Controlling the Band Gap to Improve Open-Circuit Voltage in Metal Chalcogenide based Perovskite Solar Cells

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• 作者：Meng Yuan ; Xiaoman Zhang ; Jun Kong ; ^{hdkj@henu.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; Wenhui Zhou ; Zhengji Zhou ; Qingwen Tian ; Yuena Meng ; Sixin Wu ; Dongxing Kou ; ^{koudongxing1@163.com" class="auth_mail" title="E-mail the corresponding author} ; ^{koudongxing@henu.edu.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：perovskite ; solar cells ; hole-transport material ; metal chalcogenide ; open-circuit voltage
• 刊名：Electrochimica Acta
• 出版年：2016
• 出版时间：10 October 2016
• 年：2016
• 卷：215
• 期：Complete
• 页码：374-379
• 全文大小：1072 K

文摘

Both recombination and band-edge shift are important factors for the open-circuit voltage (V_oc) improvement of metal chalcogenide hole-transport material (HTM) based perovskite solar cells, but it is still not clear that which aspect plays the dominant role in such devices. Herein, we addressed this aspect through employing the band-tunable metal chalcogenide Cu₂ZnSnS₄ (CZTS) QDs as HTM into perovskite solar cells. By replacing sulfur with selenium atom, the band gap of HTM was tuned from 1.64 eV to 1.14 eV and their influences on cell performances were further discussed. Though the Cu₂ZnSnSe₄ (CZTSe) device with higher hole transport ability could improve the fill factor (FF), its V_oc was still remarkably lower than that of the CZTS device. Electrochemical impedance spectroscopy (EIS) measurements indicated that the V_oc loss (45 mV) induced by recombination here was far less than the V_oc differences between the two devices (140 mV). After analyzing the band level alignment at TiO₂/CH₃NH₃PbI₃/HTM heterojunction, we proposed that the V_oc enhancement of CZTS device was mainly ascribed to the more downward valence band-edge shift of HTM. This further approves that developing a wide band gap material without hindering charge injection is more pressing rather than depressing recombination process for future metal chalcogenide HTM researches.