Back interface passivation for ultrathin Cu(In,Ga)Se_(2) solar cells with Schottky back contact: A trade-off of electrical effects

Back interface passivation reduces the back recombination of photogenerated electrons, whereas aggravates the blocking of hole transport towards back contact, which complicate the back interface engineering for ultrathin CIGSe solar cells with a Schottky back contact. In this work, theoretical explorations were conducted to study how the two contradictory electrical effects impact cell performance. For ultrathin CIGSe solar cells with a pronounced Schottky potential barrier(E_(h)> 0.2 eV), back interface passivation produces diverse performance evolution trends, which are highly dependent on cell structures and properties. Since a back Ga grading can screen the effect of reduced recombination of photogenerated electrons from back interface passivation, the hole blocking effect predominates and back interface passivation is not desirable. However, when the back Schottky diode merges with the main pn junction due to a reduced absorber thickness,the back potential barrier and the hole blocking effect is much reduced on this occasion. Consequently, cells exhibit the same efficiency evolution trend as ones with an Ohmic contact, where back interface passivation is always advantageous.The discoveries imply the complexity of back interface passivation and provide guidance to manipulate back interface for ultrathin CIGSe solar on TCOs with a pronounced Schottky back contact.

The study of a new n/p tunnel recombination junction and its application in a-Si:H/μc-Si:H tandem solar cells

This paper reports that a double N layer （a-Si：H/μc-Si：H） is used to substitute the single microcrystalline silicon n layer （n-μc-Si：H） in n/p tunnel recombination junction between subcells in a-Si：H/μc-Si：H tandem solar cells. The electrical transport and optical properties of these tunnel recombination junctions are investigated by current voltage measurement and transmission measurement. The new n/p tunnel recombination junction shows a better ohmic contact. In addition, the n/p interface is exposed to the air to examine the effect of oxidation on the tunnel recombination junction performance. The open circuit voltage and FF of a-Si：H/μc-Si：H tandem solar cell are all improved and the current leakage of the subcells can be effectively prevented efficiently when the new n/p junction is implemented as tunnel recombination junction.

High performance perovskite solar cells using TiO2 nanospindles as ultrathin mesoporous layer

Single crystal anatase TiO2 nanospindles （NSs） with highly exposed {101} facets were synthesized and employed as electron transport materials （ETMs） in perovskite solar cells （PSCs）. Time-resolved photoluminescence （TRPL） spectra revealed that the TiO2 NSs are more effective than TiO2 nanoparticles in accepting electrons from perovskite. Moreover. the TiO2 nanospindles further endowed the PSCs with good reproducibility and suppressed hysteresis. The best device with TiO2 NSs as ETMs yielded power conversion efficiency （PCE） of 19.6%, demonstrating that the home-made TiO2 NSs is a good ETM for PSCs.

Status of Selective Emitters for p-Type c-Si Solar Cells

Crystalline silicon (c-Si) solar cells have the lion share in world PV market. Solar cells made from crystalline silicon have lower conversion efficiency, hence optimization of each process steps are very important. Achieving low-cost photovoltaic energy in the coming years will depend on the development of third-generation solar cells. Given the trend towards these Si materials, the most promising selective emitter methods are identified to date. Current industrial monocrystalline Cz Si solar cells based on screen-printing technology for contact formation and homogeneous emitter have an efficiency potential of around 18.4%. Limitations at the rear side by the fully covering Al-BSF can be changed by selective emitter designs allowing a decoupling and separate optimization of the metallised and non-metallised areas. Several selective emitter concepts that are already in industrial mass production or close to it are presented, and their specialties and status concerning cell performance are demonstrated. Key issues that are considered here are the cost-effectiveness, added complexity, additional benefits, reliability and efficiency potential of each selective emitter tech- niques.

a-Si/c-Si heterojunction solar cells on SiSiC ceramic substrates

Silicon thin-film solar cells are considered to be one of the most promising cells in the future for their potential advantages, such as low cost, high efficiency, great stability, simple processing, and none-pollution. In this paper, latest progress on poly-crystalline silicon solar cells on ceramic substrates achieved by our group was reported. Rapid thermal chemical vapor deposition (RTCVD) was used to deposited poly-crystalline silicon thin films, and the grains of as-grown film were enlarged by Zone-melting Recrystallization (ZMR). As a great change in cell′s structure, traditional diffused pn homojunction was replaced by a-Si/c-Si heterojunction, which lead is to distinct improvement in cell′s efficiency. A conversion efficiency of 3.42% has been achieved on 1 cm2 a-Si/c-Si heterojunction solar cell (Isc=16.93 mA, Voc=310.9 mV, FF=0.6493, AM=1.5 G, 24 ℃), while the cell with diffused homojunction only got an efficiency of 0.6%. It indicates that a-Si emitter formed at low temperature might be more suitable for thin film cell on ceramics.

Excess Carrier Lifetime Improvement in c-Si Solar Cells by YAG:Ce^(3+)-Yb^(3+)

Ce3＋-Yb3＋ doped Y3Al5O12 （YAG） is a luminescent down-conversion material which could convert visible pho- tons to near infrared photons. In this work, YAG：Ce3＋-Yb3＋ is applied on the front surface of mass-produced mono crystalline Si solar cells. For the coated cells, the external quantum efficiencv from the visible to the near infrared is improved, and the energy conversion efficiency enhances from 11.70% to 12.2% under AMI.SG. Furthermore, the phosphor down-conversion effect on the solar cell is characterized by the microwave detected photoconductivity technique on the n-type silicon wafer under the 977nm excitation. The down-conversion materials improve the average excess carrier lifetime from 22.5μs to 24.2#s and the average surface recombi- nation velocity reduces from 424.Scm/s to 371.6cm/s, which reveal the significant reduction in excess carrier recombination by the phosphors.

Simulation of a-Si:H/c-Si heterojunction solar cells: From planar junction to local junction

In order to obtain higher conversion efficiency and to reduce production cost for hydrogenated amorphous silicon/crystalline silicon(a-Si:H/c-Si) based heterojunction solar cells, an a-Si:H/c-Si heterojunction with localized p–n structure(HACL) is designed. A numerical simulation is performed with the ATLAS program. The effect of the a-Si:H layer on the performance of the HIT(heterojunction with intrinsic thin film) solar cell is investigated. The performance improvement mechanism for the HACL cell is explored. The potential performance of the HACL solar cell is compared with those of the HIT and HACD(heterojunction of amorphous silicon and crystalline silicon with diffused junction) solar cells.The simulated results indicate that the a-Si:H layer can bring about much absorption loss. The conversion efficiency and the short-circuit current density of the HACL cell can reach 28.18% and 43.06 m A/cm^2, respectively, and are higher than those of the HIT and HACD solar cells. The great improvement are attributed to(1) decrease of optical absorption loss of a-Si:H and(2) decrease of photocarrier recombination for the HACL cell. The double-side local junction is very suitable for the bifacial solar cells. For an HACL cell with n-type or p-type c-Si base, all n-type or p-type c-Si passivating layers are feasible for convenience of the double-side diffusion process. Moreover, the HACL structure can reduce the consumption of rare materials since the transparent conductive oxide(TCO) can be free in this structure. It is concluded that the HACL solar cell is a promising structure for high efficiency and low cost.

Effect of H treatment on performance of HIT solar cells

Hydrogen is a ubiquitous element in semiconductor processing and particularly in amorphous and microcrystalline silicon where it plays a crucial role in the growth processes as well as in the material properties. Because of its low mass it can easily diffuse through the silicon network and leads to the passivation of dangling bonds but it may also play a role in the stabilization of metastable defects. Thus a lot of work has been devoted to the study of hydrogen diffusion, bonding and structure in disordered semiconductors. The sequence, deposition-exposure to H plasma-deposition was used to fabricate the microcrystalline emitter. A proper atomic H pretreatment of c-Si surface before depositions i layer was expected to clean the surface and passivatates the surface states, as a result improing the device parameters. In this study, H2 pretreatment of c-si surface was used at different time, power and temperature. It is found that a proper H pretreatment improves passivation of c-si surface and improves the device parameters by AFM and testing I-V.

Simulation and experimental study of a novel bifacial structure of silicon heterojunction solar cell for high efficiency and low cost

A novel structure of Ag gridlSiNx/n＋-c-Si/n-c-Si/i-a-Si：H/p＋-a-Si：HlTCO/Ag grid was designed to increase the ef- ficiency of bifacial amorphous/crystalline silicon-based solar cells and reduce the rear material consumption and production cost. The simulation results show that the new structure obtains higher efficiency compared with the typical bifa- cial amorphous/crystalline silicon-based solar cell because of an increase in the short-circuit current （Jsc）, while retaining the advantages of a high open-circuit voltage, low temperature coefficient, and good weak-light performance. Moreover, real cells composed of the novel structure with dimensions of 75 mm×75 mm were fabricated by a special fabrication recipe based on industrial processes. Without parameter optimization, the cell efficiency reached 21.1% with the Jsc of 41.7 mA/cm^2. In addition, the novel structure attained 28.55% potential conversion efficiency under an illumination of AM 1.5 G, 100 mW/cm^2. We conclude that the configuration of the Ag grid/SiNx/n＋-c-Si/n-c-Si/i-a-Si：H/p＋-a-Si：H/TCO/Ag grid is a promising structure for high efficiency and low cost.

Improving intrinsic stability for perovskite/silicon tandem solar cells

Monolithic hybrid halide perovskite/crystalline silicon(c-Si)tandem solar cells have demonstrated their great potential to surpass the theoretical efficiency limit of single-junction devices.However,the stability of perovskite sub-cells is inferior to that of the c-Si solar cells that have been commercialized,casting serious doubt about the lifetime of the entire device.During device operation,light and heat are inevitable,which requires special attention.Herein,we review the current understandings of the intrinsic stability of perovskite/c-Si tandems upon light and/or heat aging.First,we summarize the recent understandings regarding light facilitated ion migration,materials decomposition,and phase segregation.In addition,the reverse bias effect on the stability of tandem modules caused by uneven illumination is discussed.Second,this review also summarizes the thermalinduced degradation and mismatch issue,which underlines the system design of perovskite/c-Si tandems.Third,recent strategies to improve the intrinsic stability of perovskite/c-Si tandems under light and/or heat are reviewed,such as composition engineering,crystallinity enhancement,interface modification,material optimization,and device structure modification.At last,we present several potential research directions that have been overlooked,and hope those are helpful for future research on perovskite based tandem solar cells.

Analysis of the double-layer a-Si：H emitter with different doping concentrations for α-Si：H/c-Si heterojunction solar cells

Double-layer emitters with different doping concentrations （DLE） have been designed and prepared for amorphous silicon/crystalline silicon （ct-Si：H/c-Si） hetero- junction solar cells. Compared with the traditional single layer emitter, both the experiment and the simulation （AFORS-HET, http：//www.paper.edu.cn/html/releasepaper/2014/04/282/） prove that the double-layer emitter increases the short circuit current of the cells significantly. Based on the quantum efficiency （QE） results and the current-voltage-temperature analysis, the mechanism for the experimental results above has been investigated. The possible reasons for the increased current include the enhancement of the QE in the short wavelength range, the increase of the tunneling probability of the current transport and the decrease of the activation energy of the emitter layers.

Indium tin oxide-free inverted polymer solar cells with ultrathin metal transparent electrodes

Efficient indium tin oxide （ITO）-free inverted polymer solar cells （PSCs） were fabricated by applying ultrathin metal transparent electrodes as sunlight incident electrodes. Smooth and continuous Ag film of 4 nm thickness was developed through the introduction of a 2 nm Au seed layer. Ultrathin Ag transparent electrode with an average transmittance of up to 80% from 480 to 680 nm and a sheet resistance of 35.4Ω/sq was obtained through the introduction of a ZnO anti-reflective layer. The ultrathin metal electrode could be directly used as cathode in polymer solar cells without oxygen plasma treatment. ITO-free inverted PSCs obtained a power conversion efficiency （PCE） of 5.2% by utilizing the ultrathin metal transparent electrodes. These results demonstrated a simple method of fabricating ITO-free inverted PSCs.

超薄晶硅太阳电池表面介质纳米结构减反及陷光机理研究

该文以实现宽谱减反、吸收增强的介质纳米结构织构化表面超薄晶硅太阳电池为目标,利用时域有限差分(FDTD)方法,系统仿真不同形貌纳米结构对太阳电池宽谱减反及吸收性能的影响。同时,借助仿真所得电场强度分布数据,进一步分析介质纳米结构织构化表面的超薄晶硅电池减反及陷光机理。结果表明:基于Mie共振散射、Fabry-Perot共振等多种模式的共同作用,表面制备介质纳米结构的超薄晶硅电池对入射光的吸收能力较表面制备单层减反层的电池大大提升,在部分波段甚至超过Yablonovitch界限。

An industrial solution to light-induced degradation of crystalline silicon solar cells

Boron-oxygen defects can cause serious lightinduced degradation （LID） of commercial solar cells based on the boron-doped crystalline silicon （c-Si）, which are formed under the injection of excess carriers induced either by illumination or applying forward bias. In this contribution, we have demonstrated that the passivation process of boron-oxygen defects can be induced by applying forward bias for a large quantity of solar cells, which is much more economic than light illumination. We have used this strategy to trigger the passivation process of batches of aluminum back surface field （A1-BSF） solar cells and passivated emitter and rear contact （PERC） solar cells. Both kinds of the treated solar cells show high stability in efficiency and suffer from very little LID under further illumination at room temperature. This technology is of significance for the suppression of LID of c-Si solar cells for the industrial manufacture.

Research on ZnO/Si heterojunction solar cells

We put forward an n-ZnO/p-Si heterojunction solar cell model based on AFORS-HET simulations and provide experimental support in this article.ZnO：B（B-doped ZnO） thin films deposited by metal-organic chemical vapor deposition（MOCVD） are planned to act as electrical emitter layer on p-type c-Si substrate for photovoltaic applications.We investigate the effects of thickness,buffer layer,ZnO：B affinity and work function of electrodes on performances of solar cells through computer simulations using AFORS-HET software package.The energy conversion efficiency of the ZnO：B（n）/ZnO/c-Si（p） solar cell can achieve 17.16%（V（oc）：675.8 mV,J（sc）：30.24 mA/cm^2,FF：83.96%） via simulation.On a basis of optimized conditions in simulation,we carry out some experiments,which testify that the ZnO buffer layer of 20 nm contributes to improving performances of solar cells.The influences of growth temperature,thickness and diborane（B2H6） flow rates are also discussed.We achieve an appropriate condition for the fabrication of the solar cells using the MOCVD technique.The obtained conversion efficiency reaches2.82%（V（oc）：294.4 mV,J（sc）：26.108 mA/cm^2,FF：36.66%）.

Multifunctional semitransparent organic solar cells with excellent infrared photon rejection

Semitransparent organic solar cells(ST-OSCs)have the potentials to open promising applications that differ from those of conventional inorganic ones,such as see-through power windows with both energy generation and heat insulation functions.However,to achieve so,there remain significant challenges,especially for balancing critical parameters,such as power conversion efficiency(PCE),average visible transparency(AVT)and low energy infrared photon radiation rejection(IRR)to realize the full potentials of ST-OSCs.Herein,we demonstrate the new design of ST-OSCs through the rational integration of organic materials,transparent electrode and infrared photon reflector in one device.With the assistance of optical simulation,new ST-OSCs with precise layout exhibit state-of-art performance,with near 30%AVT and PCE of 7.3%,as well as an excellent IRR of over 93%(780-2500 nm),representing one of best multifunctional ST-OSCs with promising perspective for window application.

基于柔性太阳能电池和超薄水凝胶薄膜的手势识别

人们在日常生活中会用到各种各样的手势,如何将不同的手势与现有的智能可穿戴设备等结合起来对生活质量的提升有不可或缺的作用,利用太阳能相关设备的光电转换特性可以很好地解决手势识别和设备能耗问题。在柔性太阳能电池与手势识别结合的研究中,采集了5种常用手势数据,进行了Z-Score、低通滤波、滑动窗口等信号处理方法,并利用随机森林、支持向量机和神经网络等对其进行分类,成功地在小样本的基础上实现了100%的预测精度,可以证明该方法在手势识别的应用中有显著优势。

Performance improvement of c-Si solar cell by a combination of SiNx/SiOx passivation and double P-diffusion gettering treatment

SiNx/SiOx passivation and double side P-diffusion gettering treatment have been used for the fabrication of c-Si solar cells. The solar cells fabricated have high open circuit voltage and short circuit current after the double P-diffusion treatment. In addition to better surface passivation effect, SiNx/SiOx layer has lower reflectivity in long wavelength range than conventional SiNx film. As a consequence, such solar cells exhibit higher conversion efficiency and better internal quantum efficiency, compared with conventional c-Si solar cells.

TiO_2与聚合物复合薄膜的离子自组装制备及表征(英文)

在常温下,以钛酸丁酯[(C4H9O)4Ti]和聚四苯乙烯磺酸钠(PSS)作为前驱物在普通载玻片上用离子自组装法制备了TiO2纳米粒子/PSS复合薄膜,复合薄膜的透过率随镀膜次数或薄膜厚度的增加而呈现周期性变化。透射电镜(TEM)测试结果表明,TiO2呈板钛矿晶体结构,薄膜连续而均匀,TiO2的平均粒径是3.6nm。光电子能谱仪(XPS)测试结果显示,薄膜中含有Ti、O、C元素,载玻片表面完全被TiO2纳米复合薄膜所覆盖。

Bphen/Ag/Bphen复合缓冲层对有机太阳电池性能的影响

采用Bphen/Ag/Bphen作为阴极缓冲层,制备了基于CuPc/C60的有机太阳电池,研究了在有机薄膜中加入金属超薄层对器件性能的影响。结果表明,在Bphen缓冲层中加入1 nm的Ag时,器件的电子注入和传输都得到了提高。采用常用的等效电路模型,计算了缓冲层对器件性能参数的影响。发现Bphen/Ag/Bphen可以改善有机层和电极的界面接触性能,降低器件的串联电阻。此外,测试了器件的吸收光谱,研究了复合缓冲层对器件光子吸收的作用,发现加入Ag薄层后提高了器件的光吸收能力。