Zhang Wei, Zhang Fuguo, Xu Bo, Li Yuanyuan, Wang Linqin, Zhang Biaobiao, Guo Yu, Gardner James M, Sun Licheng, Kloo Lars
Department of Chemistry, Applied Physical Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
Department of Chemistry, Organic Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
ACS Appl Mater Interfaces. 2020 Jul 29;12(30):33751-33758. doi: 10.1021/acsami.0c08322. Epub 2020 Jul 14.
Despite the ubiquity and importance of organic hole-transport materials in photovoltaic devices, their intrinsic low conductivity remains a drawback. Thus, chemical doping is an indispensable solution to this drawback and is essentially always required. The most widely used p-type dopant, FK209, is a cobalt coordination complex. By reducing Co(III) to Co(II), Spiro-OMeTAD becomes partially oxidized, and the film conductivity is initially increased. In order to further increase the conductivity, the hygroscopic co-dopant LiTFSI is typically needed. However, lithium salts are normally quite hygroscopic, and thus, water absorption has been suggested as a significant reason for perovskite degradation and therefore limited device stability. In this work, we report a LiTFSI-free doping process by applying organic salts in relatively high amounts. The film conductivity and morphology have been studied at different doping amounts. The resulting solar cell devices show comparable power conversion efficiencies to those based on conventional LiTFSI-doped Spiro-OMeTAD but show considerably better long-term device stability in an ambient atmosphere.
尽管有机空穴传输材料在光伏器件中无处不在且至关重要，但其固有的低电导率仍然是一个缺点。因此，化学掺杂是解决这一缺点不可或缺的方法，基本上总是需要的。使用最广泛的p型掺杂剂FK209是一种钴配位络合物。通过将Co(III)还原为Co(II)，Spiro-OMeTAD会部分氧化，薄膜电导率最初会增加。为了进一步提高电导率，通常需要吸湿共掺杂剂LiTFSI。然而，锂盐通常具有很强的吸湿性，因此，吸水被认为是钙钛矿降解的一个重要原因，从而限制了器件的稳定性。在这项工作中，我们报告了一种通过大量应用有机盐的无LiTFSI掺杂工艺。研究了不同掺杂量下薄膜的电导率和形貌。由此制备的太阳能电池器件与基于传统LiTFSI掺杂的Spiro-OMeTAD的器件具有相当的功率转换效率，但在环境大气中显示出明显更好的长期器件稳定性。
