Cu掺杂对CdS薄膜结构、光致发光及CdS/CdTe电池性能的影响

采用化学浴沉积(CBD)法在FTO(SnO2∶F)/Glass衬底上制备了Cu掺杂的CdS薄膜.用电感耦合等离子体-原子发射光谱(ICP-AES)测得不同Cu掺杂浓度的薄膜中Cu/Cd原子比分别为0.5％、1.5％、5％.分别用X射线衍射(XRD)、扫描电镜(SEM)、光致发光谱(PL)、紫外-可见-近红外反射透射谱对薄膜样品进行表征.研究了Cu掺杂对CdS薄膜的晶体结构,微观形貌以及体内点缺陷的影响.用Cu掺杂的CdS薄膜作为N型层制备CdTe太阳能电池,研究了CdS层中Cu对电池性能的影响.     

基于CaF2/W多层膜人工双曲介质的近场热光伏器件

基于近场热辐射的热光伏器件是一种极具应用前景的热电转换器件.近场下由于倏逝波的隧穿作用,可以获得远超黑体辐射的热流及热电功率,此时辐射表面光子态密度是个关键因素.本文提出了一种具有高表面态密度的CaF₂/W多层膜人工双曲介质作为辐射器,可以针对有限温度热源获得高效热电转化效果.采用禁带宽度为0.17eV的锑化铟p-n结作为接收端,在200 K温度差和50 nm近场间隙下,理论上计算获得了超过1 kW/m的高发电功率,热电转化效率在11%以上,显著高于热电材料的能量转换效率.与纯钨热源情形相比,双曲介质具有更高的倏逝波态密度,有助于显著增强辐射热流与能量利用率.进一步研究发现,当多层膜双曲介质厚度超过140 nm时,基底的影响已经可以忽略,这对器件的实际制作非常有益.相对于纳米线阵列或自然双曲介质,本文提出的多层膜结构在制作和带宽上具有明显优势,研究结果为近场热光伏的发展起到了促进作用.     

近场热光伏和热辐射电池系统中熵的应用

近场辐射换热能够极大地提高热光伏和热辐射电池系统的输出电功率,因此研究近场热光伏和热辐射电池系统的转换效率具有重要意义。本文通过计算近场效应影响下的辐射热流和熵流,给出了近场热光伏和热辐射电池系统的最大理论转换效率,并与实际转换效率对比。结果发现在近场热光伏和热辐射电池系统中,纳米线、纳米孔两种微结构和双曲线材料相比平板和电介质,不仅有更强的辐射热流,而且有更高的理论效率。但是在实际过程中,由于近场热光伏和热辐射电池系统中光谱辐射热流的峰值频率小于电池能带间隙所对应的频率,所以其实际效率低于最大理论效率。本工作为近场热光伏和热辐射电池系统的转换效率提供了一个理论极限。     

新型硒化锑材料及其光伏器件研究进展

硒化锑(Sb₂Se₃)是一种二元单相化合物, 原料储量大、毒性低、价格便宜; 同时其禁带宽度合适(～1.15 eV), 吸光系数大(>10⁵ cm^-1), 长晶温度低, 非常适合制作新型低成本低毒的薄膜太阳能电池, 理论光电转换效率可达30%以上. 目前文献报道的Sb₂Se₃薄膜太阳能电池效率已达3.7%, 初步证明了Sb₂Se₃材料在薄膜太阳能电池应用方面的巨大潜力. 本文综述了近年来Sb₂Se₃太阳能电池的研究进展, 着重介绍了Sb₂Se₃的材料特性和薄膜制备及相关理论研究, 阐述了不同结构电池器件的研究进展, 并对其发展趋势进行了展望.     

热光伏能量转换器件的热力学极限与优化性能预测

受不可逆损失的影响,热光伏能量转换器件在高品位热能回收与利用方面受到限制.本文揭示不可逆损失来源,提供热光伏能量转换器件性能提升方案.利用半导体物理和普朗克热辐射理论,确定热光伏能量转换器件在理想条件下的最大效率.进而考虑Auger与Shockley-Reed-Hall非辐射复合和不可逆传热损失对光伏电池的电学、光学和热学特性的影响,预测热光伏器件优化性能.确定功率密度、效率和光子截止能量的优化区间.结果表明:相比于理想热光伏器件,非理想热光伏器件的开路电压、短路电流密度和效率有所降低;优化热光伏电池电压、光子截止能量和热源温度,可提升器件的功率密度和效率.通过对比发现理论与实验结果较一致,所得结果可为实际热光伏能量转换器件的研制提供理论指导.     

薄膜生长速率对有机光伏器件性能的影响

采用真空热蒸发镀膜的方法制备了酞菁铜(CuPc)和富勒烯(C60)构成的平面异质结结构光伏器件,并初步研究了CuPc薄膜生长速率对器件光伏性能的影响,我们发现以较大薄膜生长速率制备的器件表现出较大的短路电流和能量转换效率。X射线衍射和原子力显微镜观察的结果表明生长速率较大的CuPc薄膜结晶相含量较少,薄膜结构较均匀、致密、平整,这可能使得CuPc薄膜激子扩散和载流子迁移特性得到提高,也可能改善其与C60受主薄膜和ITO阳极的接触,并有利于载流子的分离和收集,从而表现出较好的光伏特性。     

有机EL器件MEH-PPV/Alq3的光伏特性

制备了ITO/MEH-PPV/Alq3/LiF/Al光伏(PV)器件. MEH-PPV和Alq3分别为电子受体和给体. 光谱响应曲线主要和Alq3的吸收光谱相匹配. 在功率为0.5 mW·cm2的紫外氙灯照射下电池的短路电流为2.4 μA·cm-2, 开路电压为2.6 V, Fill因子为0.71, 电池的能量转换效率达到0.9%. 在直流电的驱动下, 器件具有电致发光的特性并且发出明亮的桔红色光, 在15 V的直流电压驱动下, 最大亮度达到了1 000 cd·cm-2.     

基于温度测量法的光伏阵列失效组件监测系统的设计

为了解决光伏阵列电站中的光伏组件由于各种原因产生失效,不能及时发现、维护而导致较大的经济损失问题,提出了一种通过在PV组件接线盒上安装无线温度传感器,动态的监控旁路二极管温度间接监测失效组件的新方法,该方法能够在不影响光伏组件结构的情况下及时发现、定位光伏阵列中失效的光伏组件;文中对热斑效应形成和温度测量法的联系以及异常数据点的处理做了较为详细的阐述,设计了温度采集和无线传输系统的硬件电路,电路简单、可靠,成本低廉易于实现,采集精度符合设计要求;并编写了PC端的的监测系统的程序,通过对PV组件失效进行遮挡验证,结果表明基于温度测量法的光伏阵列失效组件监测系统检测结果可靠温度,易于使用。     

Enhancing the performance of thin film CdS/PbS photovoltaic solar cells

This work investigates dependence of the short-circuit current density, open-circuit voltage, fill factor and efficiency of a thin film CdS/PbS solar cell on thickness of transparent conductive oxide (TCO) layer, thickness of window layer (CdS), concentration of uncompensated acceptors (width of space-charge region), carrier lifetime in PbS and the reflectivity from metallic back contact. The effect of optical losses, front and rear recombination losses as well as the recombination losses on space-charge region are also considered in this study. As a result, by thinning the front contact layer indium tin oxide from 400 to 100 nm and window layer (CdS) from 200 to 100 nm it is possible to reduce the optical losses from 32 to 20%. The effect of electron lifetime on the internal and external quantum efficiency can be neglected at high width of the space-charge region. The maximum current density of 18.4 mA/cm² is achieved at wide space-charge region (concentration of uncompensated acceptors = 10¹⁵ cm^?3) and the longest lifetime (τ_n = 10^?6 s) where the optical and recombination losses are about 55%. The maximum efficiency of 5.17%, maximum open-circuit voltage of 417 mV and approximately fixed fill factor of 74% are yielded at optimum conditions such as: electron lifetime = 10^?6 s; concentration of uncompensated acceptors = 10¹⁶ cm^?3; thickness of TCO = 100 nm; thickness of CdS = 100 nm; velocity of surface and rear recombination = 10⁷ cm/s and thickness of absorber layer = 3 μm. When the reflectance from the back contact is 100%, the cell parameters improve and the cell efficiency records a value of 6.1% under the above conditions.     

化学水浴法制备大面积CdS薄膜及其光伏应用

采用化学水浴法制备了大面积CdS多晶薄膜,研究了薄膜的形貌、结构和光学性质,结果表明,大面积CdS多晶薄膜具有良好的均匀性,通过优化CdS多晶薄膜,制成了不同CdS窗口层厚度的CdTe小面积太阳电池,减薄CdS薄膜可有效提高器件的短路电流,改善器件性能.随后,在面积30cm×40cm的衬底上制备了全面积为993.6cm²的CdTe太阳电池组件,其27个集成单元的电学性质较为均匀,太阳电池组件的光电转换效率8.13%. 关键词： 化学水浴法(CBD) CdS薄膜 CdTe太阳电池 CdTe太阳电池组件     

Evaluation of electrical and optical characteristics of ZnO/CdS/CIS thin film solar cell

In this study, device modeling and simulation are conducted to explain the effects of each layer thickness and temperature on the performance of ZnO/CdS/CIS thin film solar cells. Also, the thicknesses of the CIS and CdS absorber layers are considered in this work theoretically and experimentally. The calculations of solar cell performances are based on the solutions of the well-known three coupling equations: the continuity equation for holes and electrons and the Poisson equation. Our simulated results show that the efficiency increases by reducing the CdS thickness. Increasing the CIS thickness can increase the efficiency but it needs more materials. The efficiency is more than 19% for a CIS layer with a thickness of 2 μm. CIS nanoparticles are prepared via the polyol route and purified through centrifugation and precipitation processes.Then nanoparticles are dispersed to obtain stable inks that could be directly used for thin-film deposition via spin coating.We also obtain x-ray diffraction(XRD) peak intensities and absorption spectra for CIS experimentally. Finally, absorption spectra for the CdS window layer in several deposition times are investigated experimentally.     

Thermally evaporated CdS/CdTe thin film solar cells: Optimization of CdCl2 evaporation treatment on absorber layer

CdCl₂ treatment is crucial in the fabrication of highly efficient CdS/CdTe thin-film solar cells. This study reports a comprehensive analysis of thermal evaporated CdS/CdTe thin-film solar cells when the CdTe absorber layer is CdCl₂ annealed at temperatures from 340 to 440 °C. Samples were characterized for structural, optical, morphological and electrical properties. The films annealed at 400 °C showed better crystallinity with a cubic zinc blende structure having large grains. Higher refractive index, optical conductivity, and absorption coefficient were recorded for the CdTe films annealed at 400 °C with CdCl₂. Optimum photoactive properties for CdS/CdTe thin-film solar cells were also obtained when samples were annealed at 400 °C for 20 min with CdCl₂, and the best device exhibited V_OC of 668.4 mV, J_SC of 13.6 mA cm⁻², FF of 53.9% and an efficiency of 4.9%.     

In-situ growth of a CdS window layer by vacuum thermal evaporation for CIGS thin film solar cell applications

Highly crystalline and transparent CdS films are grown by utilizing the vacuum thermal evaporation （VTE） method. The structural, surface morphological, and optical properties of the films are studied and compared with those prepared by chemical bath deposition （CBD）. It is found that the films deposited at a high substrate temperature （200 ℃） have a preferential orientation along （002） which is consistent with CBD-grown films. Absorption spectra reveal that the films are highly transparent and the optical band gap values are found to be in a range of 2.44 eV-2.56 eV. Culnl_xGaxSe2 （CIGS） solar cells with in-situ VTE-grown CdS films exhibit higher values of Voc together with smaller values of Jsc than those from CBD. Eventually the conversion efficiency and fill factor become slightly better than those from the CBD method. Our work suggests that the in-situ thermal evaporation method can be a competitive alternative to the CBD method, particularly in the physical- and vacuum-based CIGS technology.     

Preparation of chemically deposited thin films of CdS/PbS solar cell

The present paper reports the preparation of a solar cell which has a cross-sectional scheme: ITO/CdS/PbS, containing a commercially transparent conductive ITO; chemically deposited n-type CdS (340 nm) and absorbed layer of p-type PbS (1400 nm). The structural and optical properties of the constituent films are presented. X-ray diffraction showed that all of the thin films are polycrystalline. Using scanning electron microscopy, the present study revealed that the films have uniform surface morphology over the substrate. The solar cell was characterized by determining the open circuit voltage, short-circuit current density, and J–V under 40 mW/cm² solar radiation. The efficiency of the solar cells was 1.35%, which is much higher (0.041, 0.5 and 0.1–0.4%) and slightly smaller (1.65%) than some solar cells reported in the literature.     

Deep level transient spectroscopy investigation of deep levels in CdS/CdTe thin film solar cells with Te:Cu back contact

Deep levels in Cds/CdTe thin film solar cells have a potent influence on the electrical property of these devices. As an essential layer in the solar cell device structure, back contact is believed to induce some deep defects in the CdTe thin film. With the help of deep level transient spectroscopy (DLTS), we study the deep levels in CdS/CdTe thin film solar cells with Te:Cu back contact. One hole trap and one electron trap are observed. The hole trap H1, localized at E_v+0.128~eV, originates from the vacancy of Cd (V_Cd. The electron trap E1, found at E_c-0.178~eV, is considered to be correlated with the interstitial Cu_i⁼ in CdTe.     

Electronic properties and deep level transient spectroscopy of CdS/CdTe thin film solar cells

It is well known that preparing temperatures and defects are highly related to deep-level impurities. In our studies, the CdTe polycrystalline films have been prepared at various temperatures by close spaced sublimation (CSS). The different preparing temperature effects on CdS/CdTe solar cells and deep-level impurities have been investigated by I--V and C--V measurements and deep level transient spectroscopy (DLTS). By comparison, less dark saturated current density, higher carrier concentration, and better photovoltaic performance are demonstrated in a 580oC sample. Also there is less deep-level impurity recombination, because the lower hole trap concentration is present in this sample. In addition, three deep levels, E_v+0.341 eV(H4), E_v+0.226 eV(H5) and E_C-0.147 eV(E3), are found in the 580oC sample, and the possible source of deep levels is analysed and discussed.     

CdS/CdTe薄膜太阳电池的深能级瞬态谱和光致发光研究

用深能级瞬态谱和光致发光研究了无背接触层的CdS/CdTe薄膜太阳电池的杂质分布和深能级中心.得到了净掺杂浓度在器件中的分布.确定了两个能级位置分别在E_V+0365 eV和E_V+0282 eV的深中心,它们的浓度分别为167×10¹² cm^-3和386×10¹¹ cm^-2,俘获截面分别为143×10^-14cm²和153×10^-16cm².它们来源于以化学杂质形式存在的Au和（或）Te_Cd^-复合体,或与氩氧气氛下沉积CdTe时的氧原子相关. 关键词： 深能级瞬态谱 光致发光 CdS/CdTe太阳电池     

Synthesis of nanocrystalline CdS thin film by SILAR and their characterization

Cadmium sulphide (CdS) thin film was prepared by successive ion layer adsorption and reaction (SILAR) technique using ammonium sulphide as anionic precursor. Characterization techniques of XRD, SEM, TEM, FTIR and EDX were utilized to study the microstructure of the films. Structural characterization by x-ray diffraction reveals the polycrystalline nature of the films. Cubic structure is revealed from X-ray diffraction and selected area diffraction (SAD) patterns. The particle size estimated using X-ray line broadening method is approximately 7 nm. Instrumental broadening was taken into account while particle size estimation. TEM shows CdS nanoparticles in the range 5–15 nm. Elemental mapping using EFTEM reveals good stoichiometric composition of CdS. Characteristic stretching vibration mode of CdS was observed in the absorption band of FTIR spectrum. Optical absorption study exhibits a distinct blue shift in band gap energy value of about 2.56 eV which confirms the size quantization.