Shen Honglie

Effect of emitter layer doping concentration on the performance of a silicon thin film heterojunction solar cell

A novel type of n/i/i/p heterojunction solar cell with a-Si:H(15 nm)/a-Si:H(10 nm)/ epitaxial c-Si(47 μm)/epitaxial c-Si(3 μm) structure is fabricated by using the layer transfer technique, and the emitter layer is deposited by hot wire chemical vapour deposition. The effect of the doping concentration of the emitter layer Sd (Sd=PH3/(PH3+SiH4+H2)) on the performance of the solar cell is studied by means of current density—voltage and external quantum efficiency. The results show that the conversion efficiency of the solar cell first increases to a maximum value and then decreases with Sd increasing from 0.1% to 0.4%. The best performance of the solar cell is obtained at Sd = 0.2% with an open circuit voltage of 534 mV, a short circuit current density of 23.35 mA/cm2, a fill factor of 63.3%, and a conversion efficiency of 7.9%.

Effect of thermal pretreatment of metal precursor on the properties of Cu2ZnSnS4 films

Zn/Sn/Cu (CZT) stacks were prepared by RF magnetron sputtering. The stacks were pretreated at different temperatures (200 °C, 300 °C, 350 °C, and 400 °C) for 0.5 h and then followed by sulfurization at 500 °C for 2 h. Then, the structures, morphologies, and optical properties of the as-obtained Cu2ZnSnS4 (CZTS) films were studied by x-ray diffraction (XRD), Raman spectroscopy, UV–Vis–NIR, scanning electron microscope (SEM), and energy-dispersive x-ray spectroscopy (EDX). The XRD and Raman spectroscopy results indicated that the sample pretreated at 350 °C had no secondary phase and good crystallization. At the same time, SEM confirmed that it had large and dense grains. According to the UV–Vis–NIR spectrum, the sample had an absorption coefficient larger than 104 cm−1 in the visible light range and a band gap close to 1.5 eV.

Structural and Magnetic Properties of Codoped ZnO based Diluted Magnetic Semiconductors

Zn1-xCoxO (x = 0.01, 0.02, 0.05, 0.10 and 0.20) diluted magnetic semiconductors are prepared by the sol-gel method. The structural and magnetic properties of the samples are studied using x-ray diffraction (XRD), extended x-ray absorption fine structure (EXAFS) and superconducting quantum interference device (SQUID). The XRD patterns does not show any signal of precipitates that are different from wurtzite type ZnO when Co content is lower than x = 0.10. An EXAFS technique for the Co K-edge has been employed to probe the local structures around Co atoms doped in ZnO powders by fluorescence mode. The simulation results for the first shell EXAFS signals indicate that Zn sites can be substituted by Co atoms when Co content is lower than x = 0.05. The SQUID results show that the samples (x < 0.05) exhibit clear hysteresis loops at 300 K, and magnetization versus temperature from 5 K to 350 K at H = 100 Oe for the sample x = 0.02 shows that the samples have ferromagnetism above room temperature. A double-exchange mechanism is proposed to explain the ferromagnetic properties of the samples.

β-FeSi2 as the bottom absorber of triple-junction thin-film solar cells: A numerical study

Using β-FeSi2 as the bottom absorber of triple-junction thin-film solar cells is investigated by a numerical method for widening the long-wave spectral response. The presented results show that the β-FeSi2 subcell can contribute 0.273 V of open-circuit voltage to the a-Si/μc-Si/μ-FeSi2 triple-junction thin-film solar cell. The optimized absorber thicknesses for a-Si, μc-Si, and β-FeSi2 subcells are 260 nm, 900 nm, and 40 nm, respectively. In addition, the temperature coefficient of the conversion efficiency of the a-Si/μc-Si/β-FeSi2 cell is −0.308%/K, whose absolute value is only greater than that of the a-Si subcell. This result indicates that the a-Si/μc-Si/β-FeSi2 triple-junction solar cell has a good temperature coefficient. As a result, using β-FeSi2 as the bottom absorber can improve the thin-film solar cell performance, and the a-Si/βc-Si/β-FeSi2 triple-junction solar cell is a promising structure configuration for improving the solar cell efficiency.

The Influence of Mg Doping Amount on the Property of Zn1-xMgxO Buffer Layer and Its Application in Cu(In,Ga)Se2 Solar Cells

采用低成本溶胶凝胶旋涂法制备了不同Mg含量的Zn1-xMgxO薄膜, 用其代替传统化学水浴法制备的CdS作为铜铟镓硒(Cu(In, Ga)Se2, CIGS)薄膜太阳电池的缓冲层材料.用X射线衍射仪、原子力显微镜、紫外可见吸收光谱和X射线光电子能谱仪等研究了Mg掺杂量对Zn1-xMgxO薄膜的结构、形貌、光学性能及Zn1-xMgxO/CIGS异质结之间能带排列的影响.结果表明:所制备的Zn1-xMgxO薄膜均为非晶结构; 随着Mg掺入量的增加, Zn1-xMgxO薄膜的表面形貌由条纹状变为六方形纳米颗粒, 表面粗糙度由23.53 nm减小到1.14 nm; 光学带隙值由3.55 eV增大到3.62 eV; Zn1-xMgxO/CIGS之间的导带偏移值由+0.68 eV减小到-0.33 eV, 导带排列由“尖峰状”变为“悬崖状”; 当配制的溶液中Mg源和Zn源的摩尔比为0.1时, 所制备的Zn0.82Mg0.18O/CIGS之间的导带偏移值为+0.22 eV, 电池效率最高, 达5.83%.

Influence of Solution pH Value on Photoelectric Property of CdxZn1-xS Film Prepared by Chemical Bath Deposition

采用氯化镉、氯化锌、硫脲、柠檬酸钠和氨水的溶液体系通过化学浴沉积法合成Cd x Zn 1- x S薄膜，利用X射线衍射分析、扫描电子显微镜、能谱仪和紫外可见近红外分光光度计等表征手段研究了Cd x Zn 1- x S薄膜的形貌、相结构和光学性能，测试了薄膜的光电流响应曲线并对薄膜的光电性能进行了分析.结果表明：在pH值为10至13范围内成功制备了均匀的Cd x Zn 1- x S薄膜；随着pH值升高，薄膜中Zn原子比例与光学带隙减小；制备的薄膜均表现出明显的光电导现象.pH值为11和12时薄膜的表面最为平整致密，结晶性最好，光学带隙分别为2.92 eV和2.72 eV，光暗电导比均为1.20，光源关闭后电流下降过程最快，10 s后电流分别下降了约68.55%和69.39%.