Effects of cadmium alloying on solution-processed CZTSSe solar cells:morphology,band alignment and efficiency improvement  

镉合金化对溶液法制备CZTSSe太阳电池的影响:形貌、能带排列和效率提高

作　　者：Yuanyuan Zheng Chunxu Xiang Yuancai Gong Yize Li Shiliang Xiao Haoyu Guo Chengfeng Ma Shaoying Wang Weibo Yan Wei Huang Hao Xin 郑媛元;相春旭;龚元才;李沂泽;肖仕梁;郭浩宇;马乘风;王少荧;闫伟博;黄维;辛颢(State Key Laboratory for Organic Electronics and Information Displays,Institute of Advanced Materials,Nanjing University of Posts&Telecommunications,Nanjing 210023,China)

机构地区：[1]State Key Laboratory for Organic Electronics and Information Displays,Institute of Advanced Materials,Nanjing University of Posts&Telecommunications,Nanjing 210023,China

出　　处：《Science China Materials》2025年第2期523-530,共8页中国科学(材料科学)(英文版)

基　　金：supported by the National Key Research and Development Program of China (2019YFE0118100);the National Natural Science Foundation of China (U1902218 and 22075150)。

摘　　要：Kesterite Cu2ZnSn(S,Se)4(CZTSSe)thin-film solar cells are considered promising candidates for sustainable photovoltaic applications due to their high theoretical efficiency and the abundance of low-toxicity elements.However,their performance is hindered by CuZn antisite defects and associated defect clusters,which contribute to harmful band tailing and non-radiative recombination.Substituting Zn with Cd,which has a larger ionic radius,has been shown to effectively suppress non-radiative recombination,achieving efficiencies of up to 11.73%.However,the effect of Cd alloying on absorber morphology,electronic properties,and device performance has not yet been fully explored.In this work,using the Cu^(+)-Sn^(4+)-dimethyl sulfoxide(DMSO)solution as a platform,we have successfully incorporated Cd^(2+)into the lattice of CZTSSe across the full concentration range,enabling a systematic investigation of the Cd alloying effect.The results show that Cd alloying promotes grain growth,resulting in a flat and compact film at low concentration,but excessive grain growth at high concentration.Furthermore,low Cd content inhibits lattice disorder,thereby reducing band tailing.Incorporation of Cd is found to linearly reduce the band gap by raising the valence band maximum and lowering the conduction band minimum,which increases the conduction band offset(CBO)at the heterojunction,but the CBO remains a relatively ideal value(<0.3 eV)at low Cd content(<50%).Notably,the 5%Cd alloyed CZTSSe solar cell achieved 13.31%efficiency without an anti-reflective coating,owing to the improved film properties,ideal CBO(<0.24 eV),and suppressed interface recombination.This represents an over 7.0%improvement compared to the intrinsic device performance without Cd alloying.However,high-concentration Cd alloying can damage the absorber,leading to void formation within the grains and the crystal structure transition from kesterite to stannite at 50%Cd,resulting in significant device performance degradation.锌黄锡矿结构的Cu2ZnSn(S,Se)4(CZTSSe)薄膜太阳能电池因其理论效率高、地球丰富且低毒性的元素组成而被认为是可持续光伏应用的有前景的候选者.然而,其性能受到CuZn反位缺陷及相关缺陷簇的制约,因为这些缺陷会造成有害的能带拖尾和非辐射复合.用具有较大离子半径的Cd替代Zn已被证明能有效抑制非辐射复合,最高可实现11.73%的效率.然而,Cd合金化对CZTSSe电池吸收层形貌、电学性能和器件性能的影响尚未得到充分研究.在本工作中,采用Cu^(+)Sn^(4+)-DMSO溶液体系,我们成功地在全浓度范围内将Cd^(2+)引入到CZTSSe晶格中,系统地研究了Cd合金化的作用.结果表明,Cd合金化促进了晶粒生长,在低浓度时能得到平整紧密的吸收层薄膜,但在高浓度时则出现过度晶粒生长.此外,低Cd含量能够抑制晶格无序,从而减少能带拖尾.Cd的掺入可以通过提高价带顶和降低导带底来线性降低带隙,从而增加异质结的导带偏移(CBO),但在低Cd含量(<50%)时仍保持相对理想的值(<0.3 eV).特别是在Cd合金化浓度为5%时,CZTSSe太阳能电池实现了13.31%的最佳效率(无减反层),相较于未合金化的原始器件性能提高了超过7.0%,这归功于改善的薄膜性能、理想的CBO (<0.24 eV)和界面复合的有效抑制.然而,高浓度Cd合金化可能会导致吸收层薄膜质量变差,出现大量空洞,而且在50%Cd合金化时,晶体结构从锌黄锡矿结构转变为黄锡矿结构,导致器件性能显著恶化.

关 键 词：CZTSSe solar cells Cd alloying CZTSSe/CdS band tailing 

分 类 号：TM914.4[电气工程—电力电子与电力传动]