Al_(2)O_(3)与SnO_(2)对碲化镉太阳能电池前电极的界面钝化作用  

Interface passivation by Al_(2)O_(3)and SnO_(2) at the CdTe solar cell front contact

作　　者：郑根华 王东明 吴玲玲 王光伟 蔡彦博 王德亮 ZHENG Genhua;WANG Dongming;WU Lingling;WANG Guangwei;CAI Yanbo;WANG Deliang(Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China)

机构地区：[1]中国科学技术大学合肥微尺度物质科学国家研究中心,安徽合肥230026

出　　处：《中国科学技术大学学报》2020年第4期450-456,共7页JUSTC

基　　金：国家自然科学基金(61774140,61474103)资助.

摘　　要：采用磁控溅射法分别生长Al_(2)O_(3)和SnO_(2),将其作为MgxZn_(1-x)O(MZO)/CdTe薄膜太阳能电池前电极钝化层进行了相关研究.时间分辨光致发光(TRPL)光谱的测试结果显示,MZO/Al_(2)O_(3)/CdTe的少子寿命远大于MZO/CdTe的少子寿命,表明Al_(2)O_(3)对CdTe太阳能电池具有较好的钝化作用.实验发现,以Al_(2)O_(3)为钝化层的电池亮态电流密度-电压曲线出现了严重的“S-kink”现象.通过X射线光电子能谱(XPS)分析不同钝化层电池界面的能带匹配,发现Al_(2)O_(3)和CdTe界面较高的导带带阶是造成亮态电流密度-电压曲线出现“S-kink”的主要原因之一.SnO_(2)和CdTe界面处具有较小的导带带阶,通过控制SnO_(2)薄膜厚度,可以利用量子尺寸效应调整SnO_(2)和CdTe界面处的导带带阶,减弱电流密度-电压曲线的“S-kink”现象,提升电池填充因子和短路电流密度,使得电池转化效率提升至9.7%.研究结果表明,较大的导带带阶是导致“S-kink”产生的主要原因,适当降低导带带阶,能有效改善“S-kink”现象,进而有效地提升电池转化效率.Al_(2)O_(3)and SnO_(2)thin layers employed as the passivation layer for MgxZn_(1-x)O(MZO)/CdTe thin-film solar cells were grown by RF magnetron sputtering.Time-resolved photoluminescence(TRPL)spectroscopy spectra show that the minority carrier lifetime of the MZO/Al_(2)O_(3)/CdTe structure is much longer than that of the MZO/CdTe structure,indicating that Al_(2)O_(3)has a strong passivation effect on CdTe.However,the CdTe solar cells with Al_(2)O_(3)as the passivation layer demonstrate serious“S-kink”in the light current density-voltage curves.The band alignment of solar cells with different passivation layer were analyzed by X-ray photoelectron spectroscopy(XPS).The large conduction band offset between Al_(2)O_(3)and CdTe was found to be responsible for the“S-kink”for the solar cells with Al_(2)O_(3).By controlling the thickness of the SnO_(2)layer,quantum size effect can be used to adjust the conduction band offset between SnO_(2)and CdTe,thus reducing the“S-kink”phenomenon,improving the filling factor and short-circuit current density.A solar cell with an efficiency of 9.7%has been fabricated.This study demonstrates that large conduction band offset is the main reason for the“S-kink”in the J-V curves,and that reducing the conduction band offset can effectively decrease the“S-kink”phenomenon and increase the solar cell efficiency.

关 键 词：碲化镉 薄膜太阳能电池 钝化 能带调制 

分 类 号：TM914.42[电气工程—电力电子与电力传动]