The incubation layers in microcrystalline silicon films (μc-Si:H) are studied in detail. The incubation layers in μc- Si:H films are investigated by biracial Raman spectra, and the results indicate that either d...The incubation layers in microcrystalline silicon films (μc-Si:H) are studied in detail. The incubation layers in μc- Si:H films are investigated by biracial Raman spectra, and the results indicate that either decreasing silane concentration (SC) or increasing plasma power can reduce the thickness of incubation layer. The analysis of the in-situ diagnosis by plasma optical emission spectrum (OES) shows that the emission intensities of the SiH*(412 nm) and Hα (656 nm) lines are time-dependent, thus SiH*/Hα ratio is of temporal evolution. The variation of SiH*/Hα ratio can indicate the variation in relative concentration of precursor and atomic hydrogen in the plasma. And the atomic hydrogen plays a crucial role in the formation of μc-Si:H; thus, with the plasma excited, the temporal-evolution SiH*/Hα ratio has a great influence on the formation of an incubation layer in the initial growth stage. The fact that decreasing the SC or increasing the plasma power can decrease the SIH*/Hα ratio is used to explain why the thickness of incubation layer can reduce with decreasing the SC or increasing the plasma power.展开更多
In this paper intrinsic microcrystalline silicon films have been prepared by very high frequency plasma enhanced chemical vapour deposition (VHF-PECVD) with different substrate temperature and pressure. The film pro...In this paper intrinsic microcrystalline silicon films have been prepared by very high frequency plasma enhanced chemical vapour deposition (VHF-PECVD) with different substrate temperature and pressure. The film properties were investigated by using Raman spectra, x-ray diffraction, scanning electron microscope (SEM), and optical transmittance measurements, as well as dark conductivity. Raman results indicate that increase of substrate temperature improves the microcrystallinity of the film. The crystallinity is improved when the pressure increases from 50Pa to 80Pa and the structure transits from microcrystalline to amorphous silicon for pressure higher than 80Pa. SEM reveals the effect of substrate temperature and pressure on surface morphology.展开更多
This paper studies the effects of silane back diffusion in the initial plasma ignition stage on the properties of microcrystalline silicon (μc-Si:H) films by Raman spectroscopy and spectroscopic ellipsometry, thro...This paper studies the effects of silane back diffusion in the initial plasma ignition stage on the properties of microcrystalline silicon (μc-Si:H) films by Raman spectroscopy and spectroscopic ellipsometry, through delaying the injection of SiH4 gas to the reactor before plasma ignition. Compared with standard discharge condition, delayed SiH4 gas condition could prevent the back diffusion of Sill4 from the reactor to the deposition region effectively, which induced the formation of a thick amorphous incubation layer in the interface between bulk film and glass substrate. Applying this method, it obtains the improvement of spectral response in the middle and long wavelength region by combining this method with solar cell fabrication. Finally, results are explained by modifying zero-order analytical model, and a good agreement is found between the model and experiments concerning the optimum delayed injection time.展开更多
The structural un-uniformity of microcrystalline silicon, thin film, amorphous incubation layerc-Si:H films prepared using very high frequency plasma-enhanced chemical vapour deposition method has been investigated ...The structural un-uniformity of microcrystalline silicon, thin film, amorphous incubation layerc-Si:H films prepared using very high frequency plasma-enhanced chemical vapour deposition method has been investigated by Raman spectroscopy, spectroscopic ellipsometer and atomic force mi- croscopy. It was found that the formation of amorphous incubation layer was caused by the back diffusion of SiH4 and the amorphous induction of glass surface during the initial ignition process, and growth of the incubation layer can be suppressed and uniform μc-Si:H phase is generated by the application of delayed initial SiH4 density and silane profiling methods.展开更多
This paper studies boron contamination at the interface between the p and i layers of μc-Si:H solar cells deposited in a single-chamber PECVD system. The boron depth profile in the i layer was measured by Secondary ...This paper studies boron contamination at the interface between the p and i layers of μc-Si:H solar cells deposited in a single-chamber PECVD system. The boron depth profile in the i layer was measured by Secondary Ion Mass Spectroscopy. It is found that the mixed-phase μc-Si:H materials with 40% crystalline volume fraction is easy to be affected by the residual boron in the reactor. The experimental results showed that a 500-nm thick μc-Si:H covering layer or a 30-seconds of hydrogen plasma treatment can effectively reduce the boron contamination at the p/i interface. However, from viewpoint of cost reduction, the hydrogen plasma treatment is desirable for solar cell manufacture because the substrate is not moved during the hydrogen plasma treatment.展开更多
This paper investigates several pretreatment techniques used to reduce the phosphorus contamination between solar cells. They include hydrogen plasma pretreatment, deposition of a p-type doped layer, i-a-Si:H or μc...This paper investigates several pretreatment techniques used to reduce the phosphorus contamination between solar cells. They include hydrogen plasma pretreatment, deposition of a p-type doped layer, i-a-Si:H or μc-Si:H covering layer between solar cells. Their effectiveness for the pretreatment is evaluated by means of phosphorus concentration in films, the dark conductivity of p-layer properties and cell performance.展开更多
This paper reports that high-rate-deposition of microcrystalline silicon solar cells was performed by very-highfrequency plasma-enhanced chemical vapor deposition. These solar cells, whose intrinsic μc-Si:H layers w...This paper reports that high-rate-deposition of microcrystalline silicon solar cells was performed by very-highfrequency plasma-enhanced chemical vapor deposition. These solar cells, whose intrinsic μc-Si:H layers were prepared by using a different total gas flow rate (Ftotal), behave much differently in performance, although their intrinsic layers have similar crystalline volume fraction, opto-electronic properties and a deposition rate of - 1.0 nm/s. The influence of Ftotal on the micro-structural properties was analyzed by Raman and Fourier transformed infrared measurements. The results showed that the vertical uniformity and the compact degree of μc-Si:H thin films were improved with increasing Ftotal. The variation of the microstructure was regarded as the main reason for the difference of the J V parameters. Combined with optical emission spectroscopy, we found that the gas temperature plays an important role in determining the microstructure of thin films. With Ftotal of 300 sccm, a conversion efficiency of 8.11% has been obtained for the intrinsic layer deposited at 8.5 A/s (1 A=0.1 nm).展开更多
The plasma parameters in ICP-CVD system with internal low inductance antennas(LIA) were diagnosed by Langmuir probe.The ions density(Ni) reached 1011-1012 cm-3,and the electron temperature(Te) was below ca.2 eV,...The plasma parameters in ICP-CVD system with internal low inductance antennas(LIA) were diagnosed by Langmuir probe.The ions density(Ni) reached 1011-1012 cm-3,and the electron temperature(Te) was below ca.2 eV,which was slightly decreased with applied power.A p-type hydrogenated microcrystalline silicon(μc-Si:H) film was prepared on glass substrate.After optimization of the processing parameters in flow ratio of SiH4:B2H6:H2,a high quality μc-Si:H film with deposition rate above 1.0 nm/s was achieved in this work.展开更多
This paper reports that the optical emission spectroscopy (OES) is used to monitor the plasma during the deposition process of hydrogenated microcrystalline silicon films in a very high frequency plasma enhanced che...This paper reports that the optical emission spectroscopy (OES) is used to monitor the plasma during the deposition process of hydrogenated microcrystalline silicon films in a very high frequency plasma enhanced chemical vapour deposition system. The OES intensities (Sill^*, H^* and H^*β) are investigated by varying the deposition parameters. The result shows that the discharge power, silane concentrations and substrate temperature affect the OES intensities. When the discharge power at silane concentration of 4% increases, the OES intensities increase first and then are constant, the intensities increase with the discharge power monotonously at silane concentration of 6%. The SiH^* intensity increases with silane concentration, while the intensities of H^*α and H^*β increase first and then decrease. When the substrate temperature increases, the SiH^* intensity decreases and the intensities of H^*α and H^*β are constant. The correlation between the intensity ratio of IH^*α/ISiH^* and the crystalline volume fraction (Xc) of films is confirmed.展开更多
In this paper, surface photovoltage spectroscopy (SPS) is used to determine the electronic structure of the hydrogenated transition Si films. All samples are prepared by using helicon wave plasma-enhanced chemical v...In this paper, surface photovoltage spectroscopy (SPS) is used to determine the electronic structure of the hydrogenated transition Si films. All samples are prepared by using helicon wave plasma-enhanced chemical vapour deposition technique, the films exhibit a transition from the amorphous phase to the microcrystalline phase with increasing temperature. The film deposited at lower substrate temperature has the amorphous-like electronic structure with two types of dominant defect states corresponding to the occupied Si dangling bond states (D^0/D^-) and the empty Si dangling states (D+). At higher substrate temperature, the crystallinity of the deposited films increases, while their band gap energy decreases. Meanwhile, two types of additional defect states is incorporate into the films as compared with the amorphous counterpart, which is attributed to the interface defect states between the microcrystalline Si grains and the amorphous matrix. The relative SPS intensity of these two kinds of defect states in samples deposited above 300℃ increases first and decreases afterwards, which may be interpreted as a result of the competition between hydrogen release and crystalline grain size increment with increasing substrate temperature.展开更多
Raman scattering spectroscopy and scanning electron microscopy (SEM) techniques were used to determine the structural properties of two typical series of microc rystalline silicon (μc-Si:H) films deposited at differe...Raman scattering spectroscopy and scanning electron microscopy (SEM) techniques were used to determine the structural properties of two typical series of microc rystalline silicon (μc-Si:H) films deposited at different VHF plasma power and different working gas pressure by very high frequency plasma enhanced chemical v apor deposition (VHF-PECVD) technique. Raman spectra measurements show that both crystalline volume fraction Xc and average grain size d of μc-Si : H films ar e strongly affected by the two deposition conditions and are more sensitive to w orking gas pressure than VHF plasma power. SEM characterizations have further co nfirmed that VHF plasma power and working gas pressure could clearly enhance the surface roughness of μc-Si : H films ascribing to polymerization reactions, w hich is also more sensitive to working gas pressure than VHF plasma power.展开更多
Microcrystalline silicon (μc-Si:H) thin films with and without boron doping are deposited using the radio-frequency plasma-enhanced chemical vapour deposition method. The surface roughness evolutions of the silico...Microcrystalline silicon (μc-Si:H) thin films with and without boron doping are deposited using the radio-frequency plasma-enhanced chemical vapour deposition method. The surface roughness evolutions of the silicon thin films are investigated using ex situ spectroscopic ellipsometry and an atomic force microscope. It is shown that the growth exponentβ and the roughness exponent cχ are about 0.369 and 0.95 for the undoped thin film, respectively. Whereas, for the boron-doped μc-Si:H thin film, t3 increases to 0.534 and cχ decreases to 0.46 due to the shadowing effect.展开更多
We report on the development of single chamber deposition of microcrystalline and micromorph tandem solar cells directly onto low-cost glass substrates. The cells have pin single-junction or pin/pin double-junction st...We report on the development of single chamber deposition of microcrystalline and micromorph tandem solar cells directly onto low-cost glass substrates. The cells have pin single-junction or pin/pin double-junction structures on glass substrates coated with a transparent conductive oxide layer such as SnO2 or ZnO. By controlling boron and phosphorus contaminations, a single-junction microcrystalline silicon cell with a conversion efficiency of 7.47% is achieved with an i-layer thickness of 1.2 μm. In tandem devices, by thickness optimization of the microcrystalline silicon bottom solar cell, we obtained an initial conversion efficiency of 9.91% with an aluminum (Al) back reflector without a dielectric layer. In order to enhance the performance of the tandem solar cells, an improved light trapping structure with a ZnO/Al back reflector is used. As a result, a tandem solar cell with 11.04% of initial conversion efficiency has been obtained.展开更多
A possible heating effect on the process of high deposition rate microcrystalline silicon has been studied. It includes the discharge time-accumulating heating effect, discharge power, inter-electrode distance, and to...A possible heating effect on the process of high deposition rate microcrystalline silicon has been studied. It includes the discharge time-accumulating heating effect, discharge power, inter-electrode distance, and total gas flow rate induced heating effect. It is found that the heating effects mentioned above are in some ways quite similar to and in other ways very different from each other. However, all of them will directly or indirectly cause the increase of the substrate surface temperature during the process of depositing microcrystalline silicon thin films, which will affect the properties of the materials with increasing time. This phenomenon is very serious for the high deposition rate of microcrystalline silicon thin films because of the high input power and the relatively small inter-electrode distance needed. Through analysis of the heating effects occurring in the process of depositing microcrystalline silicon, it is proposed that the discharge power and the heating temperature should be as low as possible, and the total gas flow rate and the inter-electrode distance should be suitable so that device-grade high quality deposition rate microcrystalline silicon thin films can be fabricated.展开更多
Raman spectra and scanning electron microscope (SEM) techniques were used to determine the structural properties of microcrb'stalline silicon (μc-Si:H) films deposited on different substrates with the very high...Raman spectra and scanning electron microscope (SEM) techniques were used to determine the structural properties of microcrb'stalline silicon (μc-Si:H) films deposited on different substrates with the very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) technique. Using the Raman spectra, the values of crystalline volume fraction Xc and average grain size d are 86%, 12.3nm; 65%, 5.45nm; and 38%, 4.05nm, for single crystalline silicon wafer, coming 7059 glass, and general optical glass substrates, respectively. The SEM images further demonstrate the substrate effect on the film surface roughness. For the single crystalline silicon wafer and Coming 7059 glass, the surfaces of the μc-Si:H films are fairly smooth because of the homogenous growth or h'ttle lattice mismatch. But for general optical glass, the surface of the μ-Si: H film is very rough, thus the growing surface roughness affects the crystallization process and determines the average grain size of the deposited material. Moreover, with the measurements of thickness, photo and dark conductivity, photosensitivity and activation energy, the substrate effect on the deposition rate, optical and electrical properties of the μc-Si:H thin films have also been investigated. On the basis of the above results, it can be concluded that the substrates affect the initial growing layers acting as a seed for the formation of a crystalline-like material and then the deposition rates, optical and electrical properties are also strongly influenced, hence, deposition parameter optimization is the key method that can be used to obtain a good initial growing layer, to realize the deposition of μc-Si:H films with device-grade quality on cheap substrates such as general glass.展开更多
Hydrogenated microcrystalline silicon (μc-Si:H) intrinsic films and solar cells with n-i-p configuration were prepared by plasma enhanced chemical vapor deposition (PECVD). The influence of n/i and i/p buffer la...Hydrogenated microcrystalline silicon (μc-Si:H) intrinsic films and solar cells with n-i-p configuration were prepared by plasma enhanced chemical vapor deposition (PECVD). The influence of n/i and i/p buffer layers on the μc-Si:H cell performance was studied in detail. The experimental results demonstrated that the efficiency is much improved when there is a higher crystallinity at n/i interface and an optimized a-Si:H buffer layer at i/p interface. By combining the above methods, the performance of μc-Si:H single-junction and a-Si:H/μc-Si:H tandem solar cells has been significantly improved.展开更多
Microcrystalline silicon films were deposited at a high rate and low temperature using jet-type inductively coupled plasma chemical vapor deposition(jet-ICPCVD).An investigation into the deposition rate and microstr...Microcrystalline silicon films were deposited at a high rate and low temperature using jet-type inductively coupled plasma chemical vapor deposition(jet-ICPCVD).An investigation into the deposition rate and microstructure properties of the deposited films showed that a high deposition rate of over 20 nm/s can be achieved while maintaining reasonable material quality.The deposition rate can be controlled by regulating the generation rate and transport of film growth precursors.The film with high crystallinity deposited at low temperature could principally result from hydrogen-induced chemical annealing.展开更多
The effect of hydrogen plasma treatment (HPT) during the initial stage ofmicrocrystalline silicon (μc- Si) growth on the defect density of μc-Si has been investigated. Lower absorption coefficient in the 0.8-1.0...The effect of hydrogen plasma treatment (HPT) during the initial stage ofmicrocrystalline silicon (μc- Si) growth on the defect density of μc-Si has been investigated. Lower absorption coefficient in the 0.8-1.0 eV indicated less defect density compared to its counterpart without HPT. The infrared spectroscopy of μc-Si with HPT shows an increase in 2040 cm-1, which reveals more Si-H in the amorphous/crystalline interfaces. We ascribe the decrease of defect density to hydrogen passivation of the dangling bonds. Improved performance of μc-Si solar cell with HPT is due to the reduced defect density.展开更多
The role of hydrogen in hydrogenated microcrystalline silicon (μc-Si:H) thin films in deposition processes with very high frequency plasma-enhanced chemical vapour deposition (VHF-PECVD) technique have been inve...The role of hydrogen in hydrogenated microcrystalline silicon (μc-Si:H) thin films in deposition processes with very high frequency plasma-enhanced chemical vapour deposition (VHF-PECVD) technique have been investigated in this paper. With in situ optical emission spectroscopy (OES) diagnosis during the fabrication of μc-Si:H thin films under different plasma excitation frequency Ve (60MHz-90MHz), the characteristic peak intensities (IsiH*, IHα* and IHβ* ) in SiH4+H2 plasma and the ratio of (IHα* + IHβ* ) to IsiH* were measured; all the characteristic peak intensities and the ratio (IHα* + IHβ* )/IsiH* are increased with plasma excitation frequency. It is identified that high plasma excitation frequency is favourable to promote the decomposition of SiH4+H2 to produce atomic hydrogen and SiHx radicals. The influences of atomic hydrogen on structural properties and that of SiHx radicals on deposition rate of μc-Si:H thin films have been studied through Raman spectra and thickness measurements, respectively. It can be concluded that both the crystalline volume fraction and deposition rate are enhanced with the increase of plasma excitation frequency, which is in good accord with the OES results. By means of FTIR measurements, hydrogen contents of μc-Si:H thin films deposited at different plasma excitation frequency have been evaluated from the integrated intensity of wagging mode near 640 cm^-1. The hydrogen contents vary from 4% to 5%, which are much lower than those of μc-Si:H films deposited with RF-PECVD technique. This implies that μc-Si:H thin films deposited with VHF-PECVD technique usually have good stability under light-soaking.展开更多
Using plasma enhanced chemical vapor deposition(PECVD) at 13.56 MHz,a seed layer is fabricated at the initial growth stage of the hydrogenated microcrystalline silicon germanium(μc-Si1-xGex:H) i-layer.The effects o...Using plasma enhanced chemical vapor deposition(PECVD) at 13.56 MHz,a seed layer is fabricated at the initial growth stage of the hydrogenated microcrystalline silicon germanium(μc-Si1-xGex:H) i-layer.The effects of seeding processes on the growth ofμc-Si1-xGex:H i-layers and the performance ofμc-Si1-xGex:H p-i-n single junction solar cells are investigated.By applying this seeding method,theμc-Si1-xGex:H solar cell shows a significant improvement in short circuit current density(Jsc) and fill factor(FF) with an acceptable performance of blue response as aμc-Si:H solar cell even when the Ge content x increases up to 0.3.Finally,an improved efficiency of 7.05%is achieved for theμc-Si0.7Ge0.3:H solar cell.展开更多
文摘The incubation layers in microcrystalline silicon films (μc-Si:H) are studied in detail. The incubation layers in μc- Si:H films are investigated by biracial Raman spectra, and the results indicate that either decreasing silane concentration (SC) or increasing plasma power can reduce the thickness of incubation layer. The analysis of the in-situ diagnosis by plasma optical emission spectrum (OES) shows that the emission intensities of the SiH*(412 nm) and Hα (656 nm) lines are time-dependent, thus SiH*/Hα ratio is of temporal evolution. The variation of SiH*/Hα ratio can indicate the variation in relative concentration of precursor and atomic hydrogen in the plasma. And the atomic hydrogen plays a crucial role in the formation of μc-Si:H; thus, with the plasma excited, the temporal-evolution SiH*/Hα ratio has a great influence on the formation of an incubation layer in the initial growth stage. The fact that decreasing the SC or increasing the plasma power can decrease the SIH*/Hα ratio is used to explain why the thickness of incubation layer can reduce with decreasing the SC or increasing the plasma power.
文摘In this paper intrinsic microcrystalline silicon films have been prepared by very high frequency plasma enhanced chemical vapour deposition (VHF-PECVD) with different substrate temperature and pressure. The film properties were investigated by using Raman spectra, x-ray diffraction, scanning electron microscope (SEM), and optical transmittance measurements, as well as dark conductivity. Raman results indicate that increase of substrate temperature improves the microcrystallinity of the film. The crystallinity is improved when the pressure increases from 50Pa to 80Pa and the structure transits from microcrystalline to amorphous silicon for pressure higher than 80Pa. SEM reveals the effect of substrate temperature and pressure on surface morphology.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No. 2006CB202601)
文摘This paper studies the effects of silane back diffusion in the initial plasma ignition stage on the properties of microcrystalline silicon (μc-Si:H) films by Raman spectroscopy and spectroscopic ellipsometry, through delaying the injection of SiH4 gas to the reactor before plasma ignition. Compared with standard discharge condition, delayed SiH4 gas condition could prevent the back diffusion of Sill4 from the reactor to the deposition region effectively, which induced the formation of a thick amorphous incubation layer in the interface between bulk film and glass substrate. Applying this method, it obtains the improvement of spectral response in the middle and long wavelength region by combining this method with solar cell fabrication. Finally, results are explained by modifying zero-order analytical model, and a good agreement is found between the model and experiments concerning the optimum delayed injection time.
基金Project supported by the State Key Development Program for Basic Research of China(Grant No.2006CB202601)the Natural Science Research Program of the Education Bureau of Henan Province of China(Grant No.2009A140007)
文摘The structural un-uniformity of microcrystalline silicon, thin film, amorphous incubation layerc-Si:H films prepared using very high frequency plasma-enhanced chemical vapour deposition method has been investigated by Raman spectroscopy, spectroscopic ellipsometer and atomic force mi- croscopy. It was found that the formation of amorphous incubation layer was caused by the back diffusion of SiH4 and the amorphous induction of glass surface during the initial ignition process, and growth of the incubation layer can be suppressed and uniform μc-Si:H phase is generated by the application of delayed initial SiH4 density and silane profiling methods.
基金Project supported by Hi-Tech Research and Development Program of China (Grant No 2007AA05Z436)Science and Technology Support Project of Tianjin (Grant No 08ZCKFGX03500)+4 种基金National Basic Research Program of China (Grant Nos 2006CB202602 and 2006CB202603)National Natural Science Foundation of China (Grant No 60506003)Starting Project of Nankai University (Grant No J02031)International Cooperation Project Between China-Greece Government (Grant No 2006DFA62390)Program for New Century Excellent Talents in University of China (NCET)
文摘This paper studies boron contamination at the interface between the p and i layers of μc-Si:H solar cells deposited in a single-chamber PECVD system. The boron depth profile in the i layer was measured by Secondary Ion Mass Spectroscopy. It is found that the mixed-phase μc-Si:H materials with 40% crystalline volume fraction is easy to be affected by the residual boron in the reactor. The experimental results showed that a 500-nm thick μc-Si:H covering layer or a 30-seconds of hydrogen plasma treatment can effectively reduce the boron contamination at the p/i interface. However, from viewpoint of cost reduction, the hydrogen plasma treatment is desirable for solar cell manufacture because the substrate is not moved during the hydrogen plasma treatment.
基金supported by Hi-Tech Research and Development Program of China (Grant Nos.2007AA05Z436 and 2009AA050602)Science and Technology Support Project of Tianjin of China (Grant No.08ZCKFGX03500)+3 种基金National Basic Research Program of China (Grant Nos.2006CB202602 and 2006CB202603)National Natural Science Foundation of China (Grant No.60976051)International Cooperation Project between China-Greece Government (Grant Nos.2006DFA62390 and 2009DFA62580)Program for New Century Excellent Talents in University of China (Grant No.NCET-08-0295)
文摘This paper investigates several pretreatment techniques used to reduce the phosphorus contamination between solar cells. They include hydrogen plasma pretreatment, deposition of a p-type doped layer, i-a-Si:H or μc-Si:H covering layer between solar cells. Their effectiveness for the pretreatment is evaluated by means of phosphorus concentration in films, the dark conductivity of p-layer properties and cell performance.
基金supported by the National Basic Research Program of China (Grant Nos 2006CB202602 and 2006CB202603)the Tianjin Assistant Foundation for the National Basic Research Program of China (Grant No 07QTPTJC29500)the Natural Science Foundation of Tianjin (Grant No 07JCYBJC04000)
文摘This paper reports that high-rate-deposition of microcrystalline silicon solar cells was performed by very-highfrequency plasma-enhanced chemical vapor deposition. These solar cells, whose intrinsic μc-Si:H layers were prepared by using a different total gas flow rate (Ftotal), behave much differently in performance, although their intrinsic layers have similar crystalline volume fraction, opto-electronic properties and a deposition rate of - 1.0 nm/s. The influence of Ftotal on the micro-structural properties was analyzed by Raman and Fourier transformed infrared measurements. The results showed that the vertical uniformity and the compact degree of μc-Si:H thin films were improved with increasing Ftotal. The variation of the microstructure was regarded as the main reason for the difference of the J V parameters. Combined with optical emission spectroscopy, we found that the gas temperature plays an important role in determining the microstructure of thin films. With Ftotal of 300 sccm, a conversion efficiency of 8.11% has been obtained for the intrinsic layer deposited at 8.5 A/s (1 A=0.1 nm).
基金supported by National Natural Science Foundation of China(Nos.11175024,11375031),2011BAD24B01,KM 201110015008,KM 201010015005,BIGC Key Project(No.23190113051)and PHR20110516,PHR201107145
文摘The plasma parameters in ICP-CVD system with internal low inductance antennas(LIA) were diagnosed by Langmuir probe.The ions density(Ni) reached 1011-1012 cm-3,and the electron temperature(Te) was below ca.2 eV,which was slightly decreased with applied power.A p-type hydrogenated microcrystalline silicon(μc-Si:H) film was prepared on glass substrate.After optimization of the processing parameters in flow ratio of SiH4:B2H6:H2,a high quality μc-Si:H film with deposition rate above 1.0 nm/s was achieved in this work.
文摘This paper reports that the optical emission spectroscopy (OES) is used to monitor the plasma during the deposition process of hydrogenated microcrystalline silicon films in a very high frequency plasma enhanced chemical vapour deposition system. The OES intensities (Sill^*, H^* and H^*β) are investigated by varying the deposition parameters. The result shows that the discharge power, silane concentrations and substrate temperature affect the OES intensities. When the discharge power at silane concentration of 4% increases, the OES intensities increase first and then are constant, the intensities increase with the discharge power monotonously at silane concentration of 6%. The SiH^* intensity increases with silane concentration, while the intensities of H^*α and H^*β increase first and then decrease. When the substrate temperature increases, the SiH^* intensity decreases and the intensities of H^*α and H^*β are constant. The correlation between the intensity ratio of IH^*α/ISiH^* and the crystalline volume fraction (Xc) of films is confirmed.
文摘In this paper, surface photovoltage spectroscopy (SPS) is used to determine the electronic structure of the hydrogenated transition Si films. All samples are prepared by using helicon wave plasma-enhanced chemical vapour deposition technique, the films exhibit a transition from the amorphous phase to the microcrystalline phase with increasing temperature. The film deposited at lower substrate temperature has the amorphous-like electronic structure with two types of dominant defect states corresponding to the occupied Si dangling bond states (D^0/D^-) and the empty Si dangling states (D+). At higher substrate temperature, the crystallinity of the deposited films increases, while their band gap energy decreases. Meanwhile, two types of additional defect states is incorporate into the films as compared with the amorphous counterpart, which is attributed to the interface defect states between the microcrystalline Si grains and the amorphous matrix. The relative SPS intensity of these two kinds of defect states in samples deposited above 300℃ increases first and decreases afterwards, which may be interpreted as a result of the competition between hydrogen release and crystalline grain size increment with increasing substrate temperature.
基金This work was supported by National Key Basic Research and Development Programme of China(No.G2000028202 and No.G2000028203)the Science and Technology Program of Jiangmen City,Guangdong Provincethe Scientifie Research Program of Jinan University for Excellents(No.51204056).
文摘Raman scattering spectroscopy and scanning electron microscopy (SEM) techniques were used to determine the structural properties of two typical series of microc rystalline silicon (μc-Si:H) films deposited at different VHF plasma power and different working gas pressure by very high frequency plasma enhanced chemical v apor deposition (VHF-PECVD) technique. Raman spectra measurements show that both crystalline volume fraction Xc and average grain size d of μc-Si : H films ar e strongly affected by the two deposition conditions and are more sensitive to w orking gas pressure than VHF plasma power. SEM characterizations have further co nfirmed that VHF plasma power and working gas pressure could clearly enhance the surface roughness of μc-Si : H films ascribing to polymerization reactions, w hich is also more sensitive to working gas pressure than VHF plasma power.
基金Project supported by the National Key Basic Research Program of China (Grant No.2011CB201606)the National Natural Science Foundation of China (Grant No.51007082)
文摘Microcrystalline silicon (μc-Si:H) thin films with and without boron doping are deposited using the radio-frequency plasma-enhanced chemical vapour deposition method. The surface roughness evolutions of the silicon thin films are investigated using ex situ spectroscopic ellipsometry and an atomic force microscope. It is shown that the growth exponentβ and the roughness exponent cχ are about 0.369 and 0.95 for the undoped thin film, respectively. Whereas, for the boron-doped μc-Si:H thin film, t3 increases to 0.534 and cχ decreases to 0.46 due to the shadowing effect.
基金supported by the Hi-Tech Research and Development Program of China (Grant Nos. 2007AA05Z436 and 2009AA050602)the Science and Technology Support Project of Tianjin (Grant No. 08ZCKFGX03500)+2 种基金the National Natural Science Foundation of China (Grant No. 60976051)the International Cooperation Project between China–Greece Government (GrantNo. 2009DFA62580)the Program for New Century Excellent Talents in University of China (NCET-08-0295)
文摘We report on the development of single chamber deposition of microcrystalline and micromorph tandem solar cells directly onto low-cost glass substrates. The cells have pin single-junction or pin/pin double-junction structures on glass substrates coated with a transparent conductive oxide layer such as SnO2 or ZnO. By controlling boron and phosphorus contaminations, a single-junction microcrystalline silicon cell with a conversion efficiency of 7.47% is achieved with an i-layer thickness of 1.2 μm. In tandem devices, by thickness optimization of the microcrystalline silicon bottom solar cell, we obtained an initial conversion efficiency of 9.91% with an aluminum (Al) back reflector without a dielectric layer. In order to enhance the performance of the tandem solar cells, an improved light trapping structure with a ZnO/Al back reflector is used. As a result, a tandem solar cell with 11.04% of initial conversion efficiency has been obtained.
基金Project supported by Hi-Tech Research and Development Program of China (Grant Nos. 2007AA05Z436 and 2009AA050602)Science and Technology Support Project of Tianjin (Grant No. 08ZCKFGX03500)+3 种基金National Basic Research Program of China(Grant Nos. 2006CB202602 and 2006CB202603)National Natural Science Foundation of China (Grant No. 60976051)International Cooperation Project between China-Greece Government (Grant Nos. 2006DFA62390 and 2009DFA62580)Program for New Century Excellent Talents in University of China (Grant No. NCET-08-0295)
文摘A possible heating effect on the process of high deposition rate microcrystalline silicon has been studied. It includes the discharge time-accumulating heating effect, discharge power, inter-electrode distance, and total gas flow rate induced heating effect. It is found that the heating effects mentioned above are in some ways quite similar to and in other ways very different from each other. However, all of them will directly or indirectly cause the increase of the substrate surface temperature during the process of depositing microcrystalline silicon thin films, which will affect the properties of the materials with increasing time. This phenomenon is very serious for the high deposition rate of microcrystalline silicon thin films because of the high input power and the relatively small inter-electrode distance needed. Through analysis of the heating effects occurring in the process of depositing microcrystalline silicon, it is proposed that the discharge power and the heating temperature should be as low as possible, and the total gas flow rate and the inter-electrode distance should be suitable so that device-grade high quality deposition rate microcrystalline silicon thin films can be fabricated.
基金This work was supported by the National Key Basic Research and Development Programme of China (No. G2000028202 and G2000028203) Guangdong Provincial Natural Science Foundation of China (No. 05300378) Programme on Natural Science of Jinan University (No. 51204056).
文摘Raman spectra and scanning electron microscope (SEM) techniques were used to determine the structural properties of microcrb'stalline silicon (μc-Si:H) films deposited on different substrates with the very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) technique. Using the Raman spectra, the values of crystalline volume fraction Xc and average grain size d are 86%, 12.3nm; 65%, 5.45nm; and 38%, 4.05nm, for single crystalline silicon wafer, coming 7059 glass, and general optical glass substrates, respectively. The SEM images further demonstrate the substrate effect on the film surface roughness. For the single crystalline silicon wafer and Coming 7059 glass, the surfaces of the μc-Si:H films are fairly smooth because of the homogenous growth or h'ttle lattice mismatch. But for general optical glass, the surface of the μ-Si: H film is very rough, thus the growing surface roughness affects the crystallization process and determines the average grain size of the deposited material. Moreover, with the measurements of thickness, photo and dark conductivity, photosensitivity and activation energy, the substrate effect on the deposition rate, optical and electrical properties of the μc-Si:H thin films have also been investigated. On the basis of the above results, it can be concluded that the substrates affect the initial growing layers acting as a seed for the formation of a crystalline-like material and then the deposition rates, optical and electrical properties are also strongly influenced, hence, deposition parameter optimization is the key method that can be used to obtain a good initial growing layer, to realize the deposition of μc-Si:H films with device-grade quality on cheap substrates such as general glass.
基金supported by the State Key Development Program for Basic Research of China (Nos. 2006CB202602, 2006CB202603)the Tianjin Assistant Foundation for the National Basic Research Program of China (No. 07QTPTJC29500).
文摘Hydrogenated microcrystalline silicon (μc-Si:H) intrinsic films and solar cells with n-i-p configuration were prepared by plasma enhanced chemical vapor deposition (PECVD). The influence of n/i and i/p buffer layers on the μc-Si:H cell performance was studied in detail. The experimental results demonstrated that the efficiency is much improved when there is a higher crystallinity at n/i interface and an optimized a-Si:H buffer layer at i/p interface. By combining the above methods, the performance of μc-Si:H single-junction and a-Si:H/μc-Si:H tandem solar cells has been significantly improved.
基金Project supported by the National Natural Science Foundation of China(No.60990314)the State Key Development Program for Basic Research of China(No.2007CB936300)
文摘Microcrystalline silicon films were deposited at a high rate and low temperature using jet-type inductively coupled plasma chemical vapor deposition(jet-ICPCVD).An investigation into the deposition rate and microstructure properties of the deposited films showed that a high deposition rate of over 20 nm/s can be achieved while maintaining reasonable material quality.The deposition rate can be controlled by regulating the generation rate and transport of film growth precursors.The film with high crystallinity deposited at low temperature could principally result from hydrogen-induced chemical annealing.
基金supported by the National High Technology Research and Development Program of China(No.2011AA050504)the National Natural Science Foundation of China(No.51072194)the Key Laboratory of Nanodevices and Applications,Suzhou Institute of Nano-Tech and Nano-Bionics,Chinese Academy of Sciences(No.12JG01)
文摘The effect of hydrogen plasma treatment (HPT) during the initial stage ofmicrocrystalline silicon (μc- Si) growth on the defect density of μc-Si has been investigated. Lower absorption coefficient in the 0.8-1.0 eV indicated less defect density compared to its counterpart without HPT. The infrared spectroscopy of μc-Si with HPT shows an increase in 2040 cm-1, which reveals more Si-H in the amorphous/crystalline interfaces. We ascribe the decrease of defect density to hydrogen passivation of the dangling bonds. Improved performance of μc-Si solar cell with HPT is due to the reduced defect density.
基金Project supported by the Natural Science Foundation of Guangdong Province, China (Grant No 05300378), the State Key Development Program for Basic Research of China (Grant Nos G2000028202 and G2000028203) and the Program on Natural Science of Jinan University, Guangzhou, China (Grant No 51204056).
文摘The role of hydrogen in hydrogenated microcrystalline silicon (μc-Si:H) thin films in deposition processes with very high frequency plasma-enhanced chemical vapour deposition (VHF-PECVD) technique have been investigated in this paper. With in situ optical emission spectroscopy (OES) diagnosis during the fabrication of μc-Si:H thin films under different plasma excitation frequency Ve (60MHz-90MHz), the characteristic peak intensities (IsiH*, IHα* and IHβ* ) in SiH4+H2 plasma and the ratio of (IHα* + IHβ* ) to IsiH* were measured; all the characteristic peak intensities and the ratio (IHα* + IHβ* )/IsiH* are increased with plasma excitation frequency. It is identified that high plasma excitation frequency is favourable to promote the decomposition of SiH4+H2 to produce atomic hydrogen and SiHx radicals. The influences of atomic hydrogen on structural properties and that of SiHx radicals on deposition rate of μc-Si:H thin films have been studied through Raman spectra and thickness measurements, respectively. It can be concluded that both the crystalline volume fraction and deposition rate are enhanced with the increase of plasma excitation frequency, which is in good accord with the OES results. By means of FTIR measurements, hydrogen contents of μc-Si:H thin films deposited at different plasma excitation frequency have been evaluated from the integrated intensity of wagging mode near 640 cm^-1. The hydrogen contents vary from 4% to 5%, which are much lower than those of μc-Si:H films deposited with RF-PECVD technique. This implies that μc-Si:H thin films deposited with VHF-PECVD technique usually have good stability under light-soaking.
基金supportedbytheNationalBasicResearch Program ofChina(Nos.2011CBA00705,2011CBA00706,2011CBA00707)the Natural Science Foundation of Tianjin(No.12JCQNJC01000)the Fundamental Research Funds for the Central Universities
文摘Using plasma enhanced chemical vapor deposition(PECVD) at 13.56 MHz,a seed layer is fabricated at the initial growth stage of the hydrogenated microcrystalline silicon germanium(μc-Si1-xGex:H) i-layer.The effects of seeding processes on the growth ofμc-Si1-xGex:H i-layers and the performance ofμc-Si1-xGex:H p-i-n single junction solar cells are investigated.By applying this seeding method,theμc-Si1-xGex:H solar cell shows a significant improvement in short circuit current density(Jsc) and fill factor(FF) with an acceptable performance of blue response as aμc-Si:H solar cell even when the Ge content x increases up to 0.3.Finally,an improved efficiency of 7.05%is achieved for theμc-Si0.7Ge0.3:H solar cell.