填充因子对激光组束远场功率分布的影响

根据Collins积分公式对激光组束后的远场分布进行了理论分析和模拟计算,着重讨论了参与组束激光的填充因子对组束后的远场分布的影响。

Design,Analysis,and Optimization of a CMOS Active Pixel Sensor

A three-transistor active pixel sensor and its double sampling readout circuit implemented by a switch capacitor amplifier are designed. The circuit is embedded in a 64 × 64 pixel array CMOS image sensor and success-fully taped out with a Chartered 0.35μm process. The pixel pitch is 8μm × 8μm with a fill factor of 57%, the photo-sensitivity is 0.8V/（lux · s） ,and the dynamic range is 50dB. Theoretical analysis and test results indicate that as the process is scaled down, a smaller pixel pitch reduces the sensitivity. A deep junction n-well/p-substrate photodiode with a reasonable fill factor and high sensitivity are more appropriate for submicron processes.

Excitation Spectrum of Spin-1 Bosonic Atoms in an Optical Lattice with High Filling Factors

The Green＇s function and the higher-order correlation functions of spin-1 cold atoms in an optical lattice are defined. Because we consider the problem of spin-1 Bose condensed atoms in an optical lattice with high filling factors, i.e., the number density of Bose condensed atoms no is large, the fluctuation of them can be neglected and we take mean-field approximation for the higher-order terms. The excitation spectra for both the polar case and the ferromagnetic case are obtained and analyzed.

Effect of Temperature on the Organic Solar Cells Parameters

The dependence of the organic solar cells parameters, e.g., the shirt circuit current Isc, open circuit voltage Vo,., the fill factor FF and the efficiency eta on temperature is investigated. By expressing the different equations which link the parameters with temperature, it is observed that the short circuit current Isc increases so monotonous with temperature and then saturates to a maximum value before decreasing at high temperatures. The open circuit voltage V∝ decreases linearly with the increasing of the temperature. The fill factor FF and the efficiency eta which are directly related with short circuit current Isc and the open circuit voltage V∝ follow their variations.

Alloy-like ternary polymer solar cells with over 17.2% efficiency

Ternary strategy has been considered as an efficient method to achieve high performance polymer solar cells(PSCs). A power conversion efficiency(PCE) of 17.22% is achieved in the optimized ternary PSCs with10 wt% MF1 in acceptors. The over 8% PCE improvement by employing ternary strategy is attributed to the simultaneously increased JSCof 25.68 mA cm^-2, VOCof 0.853 V and FF of 78.61% compared with Y6 based binary PSCs. The good compatibility of MF1 and Y6 can be confirmed from Raman mapping, contact angle,cyclic voltammetry and morphology, which is the prerequisite to form alloy-like state. Electron mobility in ternary active layers strongly depends on MF1 content in acceptors due to the different lowest unoccupied molecular orbital(LUMO) levels of Y6 and MF1, which can well explain the wave-like varied FF of ternary PSCs. The third-party certified PCE of 16.8% should be one of the highest values for single bulk heterojunction PSCs. This work provides sufficient references for selecting materials to achieve efficient ternary PSCs.

A low-temperature TiO2/SnO2 electron transport layer for high-performance planar perovskite solar cells

Conventional titanium oxide(TiO2) as an electron transport layer(ETL) in hybrid organic-inorganic perovskite solar cells(PSCs) requires a sintering process at a high temperature to crystalize, which is not suitable for flexible PSCs and tandem solar cells with their low-temperatureprocessed bottom cell. Here, we introduce a low-temperature solution method to deposit a TiO2/tin oxide(SnO2) bilayer towards an efficient ETL. From the systematic measurements of optical and electronic properties, we demonstrate that the TiO2/SnO2 ETL has an enhanced charge extraction ability and a suppressed carrier recombination at the ETL/perovskite interface, both of which are beneficial to photo-generated carrier separation and transport. As a result, PSCs with TiO2/SnO2 bilayer ETLs present higher photovoltaic performance of the baseline cells compared with their TiO2 and SnO2 single-layer ETL counterparts. The champion PSC has a power conversion efficiency(PCE) of 19.11% with an open-circuit voltage(Voc)of 1.15 V, a short-circuit current density(Jsc) of 22.77 mA cm^-2,and a fill factor(FF) of 72.38%. Additionally, due to the suitable band alignment of the TiO2/SnO2 ETL in the device, a high Vocof 1.18 V is achieved. It has been proven that the TiO2/SnO2 bilayer is a promising alternative ETL for high efficiency PSCs.

Highly efficient Cu_(2)ZnSn(S,Se)_(4) bifacial solar cell via a composition gradient strategy through the molecular ink

The use of transparent conducting oxide(TCO)as a substrate in Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)thin-film solar cells allows for advanced applications,such as bifacial,semitransparent,and tandem solar cells with the capability to increase power density generation.However,the efficiency of this kind of solar cell is still below 6% based on the low-cost solution process.In this work,we develop a composition gradient strategy and demonstrate a 6.82% efficient CZTSSe solar cell on F:SnO_(2)(FTO)substrate under the ambient condition.The composition gradient is realized by simply depositing the precursor inks with different Zn/Sn ratios.To verify that the high performance of the solar cell is attributed to the composition gradient strategy rather than the sole change of the Zn/Sn ratio,devices based on absorbers with varied Zn/Sn ratios are fabricated.Furthermore,the structure and surface morphology of the CZTSSe films with/without composition gradients are examined.The presence of elemental gradient through the depth of the CZTSSe films before and after annealing is confirmed by secondary ion mass spectroscopy analysis.It is found that the composition gradient enhances the crystallinity of the absorber,reduces the surface roughness as well as device parasitic losses,contributing to a higher fill factor,open-circuit voltage,and conversion efficiency.

Promising Cd-free double buffer layer in CZTSSe thin film solar cells

Zn(O,S)film is widely used as a Cd-free buffer layer for kesterite thin film solar cells due to its low-cost and eco-friendly characteristics.However,the low carrier concentration and conductivity of Zn(O,S)will deteriorate the device performance.In this work,an additional buffer layer of In2S3 is introduced to modify the properties of the Zn(O,S)layer as well as the CZTSSe layer via a post-annealing treatment.The carrier concentrations of both the Zn(O,S)and CZTSSe layers are increased,which facilitates the carrier separation and increases the open circuit voltage(VOC).It is also found that ammonia etching treatment can remove the contamination and reduce the interface defects,and there is an increase of the surface roughness of the In2S3 layer,which works as an antireflection layer.Consequently,the efficiency of the CZTSSe solar cells is improved by 24%after the annealing and etching treatments.Simulation and experimental results show that a large band offset of the In2S3 layer and defect energy levels in the Zn(O,S)layer are the main properties limiting the fill factor and efficiency of these CZTSSe devices.This study affords a new perspective for the carrier concentration enhancement of the absorber and buffer layers by In-doping,and it also indicates that In2S3/Zn(O,S)is a promising Cd-free hybrid buffer layer for high-efficiency kesterite solar cells.

Optimizing the component ratio of PEDOT:PSS by water rinse for high efficiency organic solar cells over 16.7%

For the state-of-the-art organic solar cells(OSCs),PEDOT:PSS is the most popularly used hole transport material for the conventional structure.However,it still suffers from several disadvantages,such as low conductivity and harm to ITO due to the acidic PSS.Herein,a simple method is introduced to enhance the conductivity and remove the additional PSS by water rinsing the PEDOT:PSS films.The photovoltaic devices based on the water rinsed PEDOT:PSS present a dramatic improvement in efficiency from 15.98%to 16.75%in comparison to that of the untreated counterparts.Systematic characterization and analysis reveal that although part of the PEDOT:PSS is washed away,it still leaves a smoother film and the ratio of PEDOT to PSS is higher than before in the remaining films.It can greatly improve the conductivity and reduce the damage to substrates.This study demonstrates that finely modifying the charge transport materials to improve conductivity and reduce defeats has great potential for boosting the efficiency of OSCs.

Synergistic high efficiency and low energy loss of all-small-molecule organic solar cells based on benzotriazole-basedπ-bridge unit

Reducing energy loss(V_(loss))is one of the most crucial challenges in organic photovoltaic cells.The V_(loss),determined by the differences between the optical band gap(E_(g))of the active layer material and the open-circuit voltage(V_(oc))of the device,is generally alleviated by lowering the energy difference between the lowest unoccupied molecular orbital(LUMO)and highest occupied molecular orbital(HOMO)level of the donor(D)and acceptor(A).In this work,we synthesized two A-π-D-π-A-type small-molecule donors(SMDs)SM-benzotriazole(BTz)-1 and SM-BTz-2 by introducing a BTzπ-bridge unit and terminal regulation.The BTzπ-bridge unit significantly lowers the HOMO energy level of SMDs,resulting in high V_(oc)and high mobility,achieving a balance of low energy loss(<0.5 eV)and high efficiency.Ultimately,the organic solar cells based on SM-BTz-2 as the donor and Y6 as the acceptor obtain a high V_(oc)of 0.91 V,J_(sc) of 22.8 mA cm^(−2),fill factor of 68%,and power conversion efficiency(PCE)of 14.12%,which is one of the highest efficiencies based on the SMDs with triazoleπ-bridges to date.What’s more,the BTzπ-bridge unit is a potential unit that can improve mobility and reduce energy loss.

Optimization of band gaps of 2D photonic crystals by the rapid generic algorithm

Based on the rapid genetic algorithm(RGA),the band gap structures of square lattices with square scatters are optimized.In the optimizing process,gene codes are used to express square scatters and the fitting function adopts the relative values of the largest absolute photonic band gaps(PBGs).By changing the value of filling factor,three cell forms with large photonic band gaps are obtained.In addition,the comparison between the rapid genetic algorithm and the general genetic algorithm(GGA) is analyzed.

Efficiency enhancement of P3HT:PCBM polymer solar cells using oligomers DH4T as the third component

We assembled a ternary blend bulk heterojunction polymer solar cell(PSCs) containing P3HT(donor) and PC61BM(acceptor) incorporated with a small molecule oligomer, dihexyl-quaterthiophene(DH4T) as a third component. By optimizing the contents of DH4 T, we increased the power conversion efficiency of ternary P3HT:DH4T:PC61BM PSCs to 4.17% from 3.44% of binary P3HT:PC61BM PSCs under AM 1.5 G of 100 m W/cm2 intensity. The major improvement is from the increase of the short circuit current and fill factor that is due to the increased light absorption at short wavelength, the balanced charge carrier transportation and the enhanced hole evacuation by a DH4T-enriched layer at the anode interface. In this work, we demonstrated that the efficiency of the PSCs can be enhanced by using low-bandgap conjugated polymer and its oligomer as donors and fullerene derivatives as acceptors.

Efficient organic solar cells with low-temperature in situ prepared Ga_(2)O_(3) or In_(2)O_(3) electron collection layers

Facile synthesis of an interfacial layer in organic solar cells (OSCs) is important for broadening material designs and upscaling photovoltaic conversion efficiency (PCE).Herein,a mild solution process of spin-coating In(acac)3and Ga(acac)3isopropanol precursors followed by low-temperature thermal treatment was developed to fabricate In_(2)O_(3)and Ga2O3cathode buffer layers (CBLs).The introduction of In_(2)O_(3)or Ga2O3CBLs endows PM6:Y6-based OSCs with outstanding performance and high PCEs of 16.17%and 16.01%,respectively.Comparison studies present that the In_(2)O_(3)layer possesses a work function (WF) of 4.58 eV,which is more favorable for the formation of ohmic contact compared with the Ga2O3layer with a WF of 5.06 eV and leads to a higher open circuit voltage for the former devices.Electrochemical impedance spectroscopy was performed to reveal how In_(2)O_(3)and Ga2O3affect the internal charge transfer and the origin of their performance difference.Although In_(2)O_(3)possesses lower series resistance loss,Ga2O3has a higher recombination resistance,which enhances the device fill factor and compensates for its series resistance loss to some extent.Comparative analysis of the photo-physics of In_(2)O_(3)and Ga2O3suggests that both are excellent CBLs for highly efficient OSCs.

Bilayer broadband antireflective coating to achieve planar heterojunction perovskite solar cells with23.9%efficiency

Although perovskite solar cells(PSCs)have achieved encouraging efficiency,the photon loss at the substrate due to light reflection has not been well addressed.Light management is promising to reduce reflection loss and realize higher power conversion efficiency(PCE)of PSCs.Here,a bilayer antireflective coating(ARC)has been designed and coated onto the backside of the glass substrate of(FAPbI_(3))_(x)(MAPbBr_(3))_(1-x)PSCs to enhance photon harvesting and consequently the device efficiency.The bottom layer of the bilayer ARC is made from a silica polymer and the top layer is made from the mixture of hexamethyldisiloxane-modified mesoporous silica nanoparticles and a fluorinated silica polymer.By adjusting the refractive index and the film thickness of each layer according to a two-layer model,enhanced glass transmittance in a broadband wavelength range can be reached,with the maximum transmittance increasing from ca.90%to over 95%.With the bilayer ARC,the maximum short-circuit current density and PCE of(FAPbI_(3))_(x)(MAPbBr_(3))_(1-x)PSCs can be increased from 25.5 m A cm^(-2)and 22.7%to 26.5 mA cm^(-2)and 23.9%with negligible changes in fill factor and opencircuit voltage.This work presents a simple yet effective strategy to enhance the efficiency of solar cells employing bilayer antirefective coatings,which can be applied to other types of solar cells.

Centimeter-scale perovskite SrTaO2N single crystals with enhanced photoelectrochemical performance

Large-scale single crystals have potential applications in many fields,such as in ferroelectric and photoelectric energy conversion devices.Perovskite oxynitrides have also attracted attention in photoelectrochemical water splitting systems because of their high theoretical solar-to-hydrogen efficiencies.Nevertheless,the synthesis of perovskite oxynitride single crystals requires the coupling of cation exchange and ammonization processes,which is exceptionally challenging.The present study demonstrates an inorganic vapor method that provides,for the first time ever,high-quality epitaxial perovskite SrTaO_(2)N single crystals on the centimeter scale.Assessments using Raman spectroscopy,crystal structure analysis and density functional theory determined that the conversion mechanism followed a topotactic transition mode.Compared with conventional SrTaO_(2)N particle-assembled films,the SrTaO_(2)N single crystals made in this work were free of interparticle interfaces and grain boundaries,which exhibited extremely high performance during photoelectrochemical water oxidation.In particular,these SrTaO_(2)N single crystals showed the highest photocurrent density at 0.6 V vs.RHE(1.20 mA cm^(−2)) and the highest photocurrent filling factor(47.6%)reported to date,together with a low onset potential(0.35 V vs.RHE).This onset potential was 200 mV less than that of the reported in situ SrTaO_(2)N film,and the photocurrent fill factor was improved by 2 to 3 times.