Low cost co-precipitation method was used to synthesize Cu(0-0.05)doped MgO samples with fixed concertation of Zn=0.01.X-ray diffraction(XRD)spectra confirmed the phase purity of the samples for 0≤Cu≤0.03 doping con...Low cost co-precipitation method was used to synthesize Cu(0-0.05)doped MgO samples with fixed concertation of Zn=0.01.X-ray diffraction(XRD)spectra confirmed the phase purity of the samples for 0≤Cu≤0.03 doping concentration.The secondary phase for 0.04≤Cu≤0.05 exhibited the formation of mixed metal oxides.The crystallite size was found to increase from 17.5 to 23.5 nm for 0≤Cu≤0.03 and then decreased from 22 to 18.5 nm for 0.04≤Cu≤0.05.The estimated bandgap first reduced from 5.48 to 4.88 eV and then increased from 5.21 to 5.36 eV.The morphology of the samples transformed from spheroidal shape to star-like shape.The obtained results reveal that the structural and optical property are in good agreement with the morphological transition.The peak shifting towards the lower values of vibrational frequency from 694 to 579 cm^(-1) confirms the incorporation of Cu/Zn in Mg-O lattice.The tuning of optical bandgap and structural properties with varying dopant concentration in MgO nanomaterials can be used for multifunctional modern energy storage and optoelectronic devices.展开更多
Fluorinated amorphous carbon films were deposited using microwave electron cyclotron resonance chemical vapor deposition (ECR-CVD) reactor with CF4 and C8H6 as source gas and were annealed in nitrogen ambience for the...Fluorinated amorphous carbon films were deposited using microwave electron cyclotron resonance chemical vapor deposition (ECR-CVD) reactor with CF4 and C8H6 as source gas and were annealed in nitrogen ambience for the investigating of their thermal stability .The relative concentration of C=C bond and optical bandgap were obtained by Fourier Transform Infrared (FTIR) spectroscopy and Ultraviolet-Visible (UV-VIS ) spectrum, respectively. It has been demonstrated that there is a close relationship between relative concentration of C=C bond and optical bandgap, and the films deposited at a higher microwave power have a lower optical bandgap and a better thermal stability.展开更多
The gadolinium substituted nickel-zinc ferrite nanoparticles of the composition, Ni<sub>0.5</sub>Zn<sub>0.5</sub>Gd<sub>0.05</sub>Fe<sub>1.95</sub>O<sub>4</sub&...The gadolinium substituted nickel-zinc ferrite nanoparticles of the composition, Ni<sub>0.5</sub>Zn<sub>0.5</sub>Gd<sub>0.05</sub>Fe<sub>1.95</sub>O<sub>4</sub> were prepared using sol-gel method. In order to study the effect of calcination temperature on the optical parameters, the prepared powder was divided into five parts. The first part was taken as the as-prepared sample and the remaining four parts were calcinated at different temperatures, 600°C, 700°C, 800°C & 900°C. The X-ray diffraction patterns revealed the formation of cubic spinel structure with single phase and Fd3m space group. The crystallite size was increased from 11.75 nm to 18.13 nm as the calcination temperature increased from 600 to 900°C whereas as-prepared sample exhibited 17.61 nm. The dislocation density was decreased from 7.243 × 10<sup>-3</sup> to 3.042 × 10<sup>-3</sup> nm<sup>-2</sup> as the calcination temperature increased from 600°C to 900°C. The micro strain was decreased from 10 × 10<sup>-4</sup> to 6.452 × 10<sup>-4</sup> as the calcination temperature increased from 600°C to 900°C. The characteristic absorbance peaks were obtained at 255.2 nm for the ferrite nanoparticles of as-prepared and calcinated at 600°C and 800°C whereas it was obtained as 252.8 nm for the sample calcinated at 700°C and there was no such characteristic peak in UV-visible range for the sample calcinated at 900°C;it is expected in the below 200 nm region. The optical energy gap was calculated using Kubelka-Munk equation based on Tauc’s plot and found in the range 4.100 eV to 5.389 eV. The lowest energy gap of 4.100 eV exhibited by the sample calcinated at 700°C and the highest energy gap of 5.389 eV by the sample calcinated at 900°C. It is concluded that the tunable band gaps can be obtained with varying calcination temperature.展开更多
In this article,we present a theoretical study on the sub-bandgap refractive indexes and optical properties of Sidopedβ-Ga_(2)O_(3) thin films based on newly developed models.The measured sub-bandgap refractive index...In this article,we present a theoretical study on the sub-bandgap refractive indexes and optical properties of Sidopedβ-Ga_(2)O_(3) thin films based on newly developed models.The measured sub-bandgap refractive indexes ofβ-Ga_(2)O_(3) thin film are explained well with the new model,leading to the determination of an explicit analytical dispersion of refractive indexes for photon energy below an effective optical bandgap energy of 4.952 eV for theβ-Ga_(2)O_(3) thin film.Then,the oscillatory structures in long wavelength regions in experimental transmission spectra of Si-dopedβ-Ga_(2)O_(3) thin films with different Si doping concentrations are quantitively interpreted utilizing the determined sub-bandgap refractive index dispersion.Meanwhile,effective optical bandgap values of Si-dopedβ-Ga_(2)O_(3) thin films are further determined and are found to decrease with increasing the Si doping concentration as expectedly.In addition,the sub-bandgap absorption coefficients of Si-dopedβ-Ga_(2)O_(3) thin film are calculated under the frame of the Franz–Keldysh mechanism due to the electric field effect of ionized Si impurities.The theoretical absorption coefficients agree with the available experimental data.These key parameters obtained in the present study may enrich the present understanding of the sub-bandgap refractive indexes and optical properties of impurity-dopedβ-Ga_(2)O_(3) thin films.展开更多
A series of Zn_(1-x)Cd_xO thin films have been fabricated on sapphire by pulsed-laser deposition(PLD), successfully. To investigate the effect of Cd concentration on structural and optical properties of Zn_(1-x)...A series of Zn_(1-x)Cd_xO thin films have been fabricated on sapphire by pulsed-laser deposition(PLD), successfully. To investigate the effect of Cd concentration on structural and optical properties of Zn_(1-x)Cd_xO films, x-ray diffraction(XRD),ultraviolet-visible spectroscopy(UV-vis), and x-ray photoelectron spectroscopy(XPS) are employed to characterize the films in detail. The XRD pattern indicates that the Zn_(1-x)Cd_xO thin films have high single-orientation of the c axis. The energy bandgap values of ZnCdO thin films decrease from 3.26 eV to 2.98 eV with the increasing Cd concentration(x)according to the(αhν)~2–hν curve. Furthermore, the band offsets of Zn_(1-x)Cd_xO/ZnO heterojunctions are determinated by XPS, indicating that a type-I alignment takes place at the interface and the value of band offset could be tuned by adjusting the Cd concentration.展开更多
The energy band structures, density of states, and optical properties of IliA-doped wurtzite Mg0.25Zn0.75O (IIIA= A1, Ga, In) are investigated by a first-principles method based on the density functional theory. The...The energy band structures, density of states, and optical properties of IliA-doped wurtzite Mg0.25Zn0.75O (IIIA= A1, Ga, In) are investigated by a first-principles method based on the density functional theory. The calculated results show that the optical bandgaps of Mg0.25Zn0.75O:IIIA are larger than those of Mg0.25Zn0.75O because of the Burstein-Moss effect and the bandgap renormalization effect. The electron effective mass values of Mg0.25Zn0.75O:IIIA are heavier than those of Mgo.25Zno.750, which is in agreement with the previous experimental result. The formation energies of MgZnO:Al and MgZnO:Ga are smaller than that of MgZnO:In, while their optical bandgaps are larger, so MgZnO:Al and MgZnO:Ga are suitable to be fabricated and used as transparent conductive oxide films in the ultra-violet (UV) and deep UV optoelectronic devices.展开更多
Perovskite solar cells (PSCs) based on methylammonium lead iodide (CH3NH3PbI3) have shown unprecedentedly outstanding performance in the recent years. Nevertheless, due to the weak interaction between polar CH3NH3...Perovskite solar cells (PSCs) based on methylammonium lead iodide (CH3NH3PbI3) have shown unprecedentedly outstanding performance in the recent years. Nevertheless, due to the weak interaction between polar CH3NH3+ (MA+) and inorganic PbI3 sublattices, CH3NH3PbI3 dramatically suffers from poor moisture stability, thermal decomposition and device hysteresis. As such, strong electrostatic interactions between cations and anionic frameworks are desired for synergistic improvements of the abovementioned issues. While replacements of I with Br and/or CI evidently widen optical bandgaps of perovskite materials, compositional modifications can solely be applied on cation components in order to preserve the broad absorption of solar spectrum. Herein, we review the current successful practices in achieving efficient, stable and minimally hysteretic PSCs with lead iodide perovskite systems that employ photoactive cesium lead iodide (CsPbI3), formamidinium lead iodide (HC(NH2)2PbI3, or FAPbI3), MA1-x y-zFAxCsyRbzPbI3 mixed-cation settings as well as two-dimensional butylammonium (C4H9NH3+, or BA+)/MA+, polymeric ammonium (PEI+)/MA+ co-cation layered structures. Fundamental aspects behind the stabilization of perovskite phases α-CsPbi3, α-FAPbI3, mixed-cation MA1-x-y-zFAxCsyRb2PbI3 and crystallographic alignment of (BA)2(MA)3Pb4I13 for effective light absorption and charge transport will be discussed. This review will contribute to the continuous development of photovoltaic technology based on PSCs.展开更多
The performance of organic solar cells(OSCs)is mainly related to the bulk heterojunction(BHJ)microstructure of specific active layer systems,which is often in a metastable state.A promising strategy to address the abo...The performance of organic solar cells(OSCs)is mainly related to the bulk heterojunction(BHJ)microstructure of specific active layer systems,which is often in a metastable state.A promising strategy to address the abovementioned shortcomings of BHJs is to develop single-component active layer materials.Owing to the single-component small molecule materials with defined chemical structures generally exhibit poor absorption spectra,herein we first introduced narrow bandgap Y-series acceptors into the molecular skeleton of single-component materials,and designed two molecular dyads,SM-Et-1Y and SM-Et-2Y.The optical bandgaps(E_g~(opt)s)of the two dyads are 1.364 and 1.361 eV,respectively,which are much smaller than those of previously reported single-component molecules.Consequently,the SM-Et-2Y-based single-component OSCs(SCOSCs)showed a power conversion efficiency(PCE)of 5.07%,superior to SM-Et-1Y(2.53%),which is one of the highest PCEs reported for SCOSCs to date.Moreover,both SM-Et-1Y-and SM-Et-2Y-based devices exhibited excellent photo-stability,retaining over 90%of their initial performance after 250 h of continuous illumination.Our results provide a deeper understanding of the molecular backbone and a guiding principle for the rational design or selection of non-fullerene single-component materials with suitable donor/acceptor ratios.展开更多
In organic solar cells(OSCs),it is an effective way to improve the power conversion efficiency(PCE)by adding a guest component with appropriate absorption and energy levels in the host system.Herein,a new nonfullerene...In organic solar cells(OSCs),it is an effective way to improve the power conversion efficiency(PCE)by adding a guest component with appropriate absorption and energy levels in the host system.Herein,a new nonfullerene acceptor(NFA)named TBF-2Cl was developed by the strategy of expanding theπconjugated core of 2,2’-(((4,4,9,9-tetrahexyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b’]dithiophene-2,7-diyl)bis(methaneylylidene))bis(5,6-dichloro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile(IDT-4Cl)with two benzene rings.With increase of benzene units,TBF-2Cl exhibits higher lowest unoccupied molecular orbital(LUMO)level of-3.75 eV than that of one benzene unit based NFA IDT-4Cl and fluorene core based NFA F-2Cl,which facilitates enhancing the open-circuit voltage(V_(oc))of ternary devices.Moreover,TBF-2Cl film shows a medium optical bandgap with the absorption range from 500-800 nm,being well complementary with the wide bandgap polymer donor D18 and narrow bandgap NFA CH-6F.Accordingly,a remarkable PCE of 18.92%with a high short-circuit current density(J_(sc))of 27.40 mA·cm^(-2),a fill factor(FF)of 0.749,especially an outstanding V_(oc) of 0.922 V was achieved for the optimal ternary device based on D18:TBF-2Cl:CH-6F,surpassing the binary counterpart(17.08%).The findings provide insight into the development of new guest acceptors for obtaining more efficient OSCs.展开更多
Amorphous gallium selenide (a-GaSe) semiconductor nanoparticle thin films were deposited onto well cleaned glass substrates by inert gas condensation (IGC) technique under a vacuum of 400 x 10-6 Pa (3 x 10-6 Torr...Amorphous gallium selenide (a-GaSe) semiconductor nanoparticle thin films were deposited onto well cleaned glass substrates by inert gas condensation (IGC) technique under a vacuum of 400 x 10-6 Pa (3 x 10-6 Torr). The films were characterized by different structural and optical techniques, including X-ray diffraction, field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), UV-visible absorption spectroscopy and I-V measurements. The particle size and size distribution were determined by TEM images which show the presence of spherical particles in the range of 5-50 nm in size. SEM images indicate that the a-GaSe film grown on glass substrate is almost smooth and dense. The optical properties of a-GaSe nanoparticle thin films were determined by optical absorption spectra. The optical bandgap of the film was estimated to be 2.19 eV and the transitions are allowed direct type. The electrical conductivity of the deposited films has been studied as a function of temperature. In the higher temperature range the dominance of thermally activated band conduction was observed; whereas in the low temperature ranqe the hoppinQ conduction in the band tails of localized states was found to be dominated.展开更多
文摘Low cost co-precipitation method was used to synthesize Cu(0-0.05)doped MgO samples with fixed concertation of Zn=0.01.X-ray diffraction(XRD)spectra confirmed the phase purity of the samples for 0≤Cu≤0.03 doping concentration.The secondary phase for 0.04≤Cu≤0.05 exhibited the formation of mixed metal oxides.The crystallite size was found to increase from 17.5 to 23.5 nm for 0≤Cu≤0.03 and then decreased from 22 to 18.5 nm for 0.04≤Cu≤0.05.The estimated bandgap first reduced from 5.48 to 4.88 eV and then increased from 5.21 to 5.36 eV.The morphology of the samples transformed from spheroidal shape to star-like shape.The obtained results reveal that the structural and optical property are in good agreement with the morphological transition.The peak shifting towards the lower values of vibrational frequency from 694 to 579 cm^(-1) confirms the incorporation of Cu/Zn in Mg-O lattice.The tuning of optical bandgap and structural properties with varying dopant concentration in MgO nanomaterials can be used for multifunctional modern energy storage and optoelectronic devices.
文摘Fluorinated amorphous carbon films were deposited using microwave electron cyclotron resonance chemical vapor deposition (ECR-CVD) reactor with CF4 and C8H6 as source gas and were annealed in nitrogen ambience for the investigating of their thermal stability .The relative concentration of C=C bond and optical bandgap were obtained by Fourier Transform Infrared (FTIR) spectroscopy and Ultraviolet-Visible (UV-VIS ) spectrum, respectively. It has been demonstrated that there is a close relationship between relative concentration of C=C bond and optical bandgap, and the films deposited at a higher microwave power have a lower optical bandgap and a better thermal stability.
文摘The gadolinium substituted nickel-zinc ferrite nanoparticles of the composition, Ni<sub>0.5</sub>Zn<sub>0.5</sub>Gd<sub>0.05</sub>Fe<sub>1.95</sub>O<sub>4</sub> were prepared using sol-gel method. In order to study the effect of calcination temperature on the optical parameters, the prepared powder was divided into five parts. The first part was taken as the as-prepared sample and the remaining four parts were calcinated at different temperatures, 600°C, 700°C, 800°C & 900°C. The X-ray diffraction patterns revealed the formation of cubic spinel structure with single phase and Fd3m space group. The crystallite size was increased from 11.75 nm to 18.13 nm as the calcination temperature increased from 600 to 900°C whereas as-prepared sample exhibited 17.61 nm. The dislocation density was decreased from 7.243 × 10<sup>-3</sup> to 3.042 × 10<sup>-3</sup> nm<sup>-2</sup> as the calcination temperature increased from 600°C to 900°C. The micro strain was decreased from 10 × 10<sup>-4</sup> to 6.452 × 10<sup>-4</sup> as the calcination temperature increased from 600°C to 900°C. The characteristic absorbance peaks were obtained at 255.2 nm for the ferrite nanoparticles of as-prepared and calcinated at 600°C and 800°C whereas it was obtained as 252.8 nm for the sample calcinated at 700°C and there was no such characteristic peak in UV-visible range for the sample calcinated at 900°C;it is expected in the below 200 nm region. The optical energy gap was calculated using Kubelka-Munk equation based on Tauc’s plot and found in the range 4.100 eV to 5.389 eV. The lowest energy gap of 4.100 eV exhibited by the sample calcinated at 700°C and the highest energy gap of 5.389 eV by the sample calcinated at 900°C. It is concluded that the tunable band gaps can be obtained with varying calcination temperature.
基金This study was financially supported by the National Natural Science Foundation of China(No.12074324)the Shenzhen Municipal Science and Technology Innovation Council(No.JCJY20180508163404043).
文摘In this article,we present a theoretical study on the sub-bandgap refractive indexes and optical properties of Sidopedβ-Ga_(2)O_(3) thin films based on newly developed models.The measured sub-bandgap refractive indexes ofβ-Ga_(2)O_(3) thin film are explained well with the new model,leading to the determination of an explicit analytical dispersion of refractive indexes for photon energy below an effective optical bandgap energy of 4.952 eV for theβ-Ga_(2)O_(3) thin film.Then,the oscillatory structures in long wavelength regions in experimental transmission spectra of Si-dopedβ-Ga_(2)O_(3) thin films with different Si doping concentrations are quantitively interpreted utilizing the determined sub-bandgap refractive index dispersion.Meanwhile,effective optical bandgap values of Si-dopedβ-Ga_(2)O_(3) thin films are further determined and are found to decrease with increasing the Si doping concentration as expectedly.In addition,the sub-bandgap absorption coefficients of Si-dopedβ-Ga_(2)O_(3) thin film are calculated under the frame of the Franz–Keldysh mechanism due to the electric field effect of ionized Si impurities.The theoretical absorption coefficients agree with the available experimental data.These key parameters obtained in the present study may enrich the present understanding of the sub-bandgap refractive indexes and optical properties of impurity-dopedβ-Ga_(2)O_(3) thin films.
基金supported by the National Natural Science Foundation of China(Grant No.11404302)the Laser Fusion Research Center Funds for Young Talents(Grant No.RCFPD1-2017-9)
文摘A series of Zn_(1-x)Cd_xO thin films have been fabricated on sapphire by pulsed-laser deposition(PLD), successfully. To investigate the effect of Cd concentration on structural and optical properties of Zn_(1-x)Cd_xO films, x-ray diffraction(XRD),ultraviolet-visible spectroscopy(UV-vis), and x-ray photoelectron spectroscopy(XPS) are employed to characterize the films in detail. The XRD pattern indicates that the Zn_(1-x)Cd_xO thin films have high single-orientation of the c axis. The energy bandgap values of ZnCdO thin films decrease from 3.26 eV to 2.98 eV with the increasing Cd concentration(x)according to the(αhν)~2–hν curve. Furthermore, the band offsets of Zn_(1-x)Cd_xO/ZnO heterojunctions are determinated by XPS, indicating that a type-I alignment takes place at the interface and the value of band offset could be tuned by adjusting the Cd concentration.
基金Project supported by the National Natural Science Foundation of China(Grant No.61078046)the Special Funds for Provincial Strategic and Emerging Industries Projects of Guangdong Province,China(Grant No.2012A080304016)the Youth Foundation of South China Normal University,China(Grant No.2012KJ018)
文摘The energy band structures, density of states, and optical properties of IliA-doped wurtzite Mg0.25Zn0.75O (IIIA= A1, Ga, In) are investigated by a first-principles method based on the density functional theory. The calculated results show that the optical bandgaps of Mg0.25Zn0.75O:IIIA are larger than those of Mg0.25Zn0.75O because of the Burstein-Moss effect and the bandgap renormalization effect. The electron effective mass values of Mg0.25Zn0.75O:IIIA are heavier than those of Mgo.25Zno.750, which is in agreement with the previous experimental result. The formation energies of MgZnO:Al and MgZnO:Ga are smaller than that of MgZnO:In, while their optical bandgaps are larger, so MgZnO:Al and MgZnO:Ga are suitable to be fabricated and used as transparent conductive oxide films in the ultra-violet (UV) and deep UV optoelectronic devices.
基金financial support from the U.S.National Science Foundation(CBET-1150617)financial support from the U.S.National Science Foundation REU Grant(CHE-1659548)supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,under Contract No.DE-AC02-06CH11357
文摘Perovskite solar cells (PSCs) based on methylammonium lead iodide (CH3NH3PbI3) have shown unprecedentedly outstanding performance in the recent years. Nevertheless, due to the weak interaction between polar CH3NH3+ (MA+) and inorganic PbI3 sublattices, CH3NH3PbI3 dramatically suffers from poor moisture stability, thermal decomposition and device hysteresis. As such, strong electrostatic interactions between cations and anionic frameworks are desired for synergistic improvements of the abovementioned issues. While replacements of I with Br and/or CI evidently widen optical bandgaps of perovskite materials, compositional modifications can solely be applied on cation components in order to preserve the broad absorption of solar spectrum. Herein, we review the current successful practices in achieving efficient, stable and minimally hysteretic PSCs with lead iodide perovskite systems that employ photoactive cesium lead iodide (CsPbI3), formamidinium lead iodide (HC(NH2)2PbI3, or FAPbI3), MA1-x y-zFAxCsyRbzPbI3 mixed-cation settings as well as two-dimensional butylammonium (C4H9NH3+, or BA+)/MA+, polymeric ammonium (PEI+)/MA+ co-cation layered structures. Fundamental aspects behind the stabilization of perovskite phases α-CsPbi3, α-FAPbI3, mixed-cation MA1-x-y-zFAxCsyRb2PbI3 and crystallographic alignment of (BA)2(MA)3Pb4I13 for effective light absorption and charge transport will be discussed. This review will contribute to the continuous development of photovoltaic technology based on PSCs.
基金supported by the National Natural Science Foundation of China(52061135206,22279094)the Fundamental Research Funds for the Central Universities。
文摘The performance of organic solar cells(OSCs)is mainly related to the bulk heterojunction(BHJ)microstructure of specific active layer systems,which is often in a metastable state.A promising strategy to address the abovementioned shortcomings of BHJs is to develop single-component active layer materials.Owing to the single-component small molecule materials with defined chemical structures generally exhibit poor absorption spectra,herein we first introduced narrow bandgap Y-series acceptors into the molecular skeleton of single-component materials,and designed two molecular dyads,SM-Et-1Y and SM-Et-2Y.The optical bandgaps(E_g~(opt)s)of the two dyads are 1.364 and 1.361 eV,respectively,which are much smaller than those of previously reported single-component molecules.Consequently,the SM-Et-2Y-based single-component OSCs(SCOSCs)showed a power conversion efficiency(PCE)of 5.07%,superior to SM-Et-1Y(2.53%),which is one of the highest PCEs reported for SCOSCs to date.Moreover,both SM-Et-1Y-and SM-Et-2Y-based devices exhibited excellent photo-stability,retaining over 90%of their initial performance after 250 h of continuous illumination.Our results provide a deeper understanding of the molecular backbone and a guiding principle for the rational design or selection of non-fullerene single-component materials with suitable donor/acceptor ratios.
基金supported by the Natural Science Foundation for Distinguished Young Scholars of Hubei Province of China (2023AFA065)the National Key Research and Development Program (2019YFB2205100)Hubei Province Key Scientific and Technological Project (2022AEA001)。
基金supported by the National Natural Science Foundation of China(No.52173010)Jining University(Nos.2022HHKJ11,2019BSZX01).
文摘In organic solar cells(OSCs),it is an effective way to improve the power conversion efficiency(PCE)by adding a guest component with appropriate absorption and energy levels in the host system.Herein,a new nonfullerene acceptor(NFA)named TBF-2Cl was developed by the strategy of expanding theπconjugated core of 2,2’-(((4,4,9,9-tetrahexyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b’]dithiophene-2,7-diyl)bis(methaneylylidene))bis(5,6-dichloro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile(IDT-4Cl)with two benzene rings.With increase of benzene units,TBF-2Cl exhibits higher lowest unoccupied molecular orbital(LUMO)level of-3.75 eV than that of one benzene unit based NFA IDT-4Cl and fluorene core based NFA F-2Cl,which facilitates enhancing the open-circuit voltage(V_(oc))of ternary devices.Moreover,TBF-2Cl film shows a medium optical bandgap with the absorption range from 500-800 nm,being well complementary with the wide bandgap polymer donor D18 and narrow bandgap NFA CH-6F.Accordingly,a remarkable PCE of 18.92%with a high short-circuit current density(J_(sc))of 27.40 mA·cm^(-2),a fill factor(FF)of 0.749,especially an outstanding V_(oc) of 0.922 V was achieved for the optimal ternary device based on D18:TBF-2Cl:CH-6F,surpassing the binary counterpart(17.08%).The findings provide insight into the development of new guest acceptors for obtaining more efficient OSCs.
文摘Amorphous gallium selenide (a-GaSe) semiconductor nanoparticle thin films were deposited onto well cleaned glass substrates by inert gas condensation (IGC) technique under a vacuum of 400 x 10-6 Pa (3 x 10-6 Torr). The films were characterized by different structural and optical techniques, including X-ray diffraction, field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), UV-visible absorption spectroscopy and I-V measurements. The particle size and size distribution were determined by TEM images which show the presence of spherical particles in the range of 5-50 nm in size. SEM images indicate that the a-GaSe film grown on glass substrate is almost smooth and dense. The optical properties of a-GaSe nanoparticle thin films were determined by optical absorption spectra. The optical bandgap of the film was estimated to be 2.19 eV and the transitions are allowed direct type. The electrical conductivity of the deposited films has been studied as a function of temperature. In the higher temperature range the dominance of thermally activated band conduction was observed; whereas in the low temperature ranqe the hoppinQ conduction in the band tails of localized states was found to be dominated.