Tetrabutylammonium Hydroxide-Functionalized Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXene for Significantly Improving the Photovoltaic Performance of Perovskite Solar Cells
Wei Huang, Ling Ding, Dianhui Wang, Ping Cai, Jing Wang, Ruixiang Gao, Haiqing Hu, Yashuai Ye, Chengwen Huang, Xiaogang Xue, Hongliang Peng, Lixian Sun
Abstract
An appropriate electron transport layer (ETL) or cathode buffer layer (CBL) is critical for high-performance perovskite solar cells (PVSCs). In this work, tetrabutylammonium hydroxide (TBAOH)-functionalized Ti 3 C 2 T x MXene (TBAOH-Ti 3 C 2 T x ) is developed to improve the photovoltaic performance of PVSCs. TBAOH-Ti 3 C 2 T x is synthesized by HF etching and then TBAOH intercalation, and TBAOH can effectively attach to the Ti 3 C 2 T x surface during the intercalation process. In hole transport material (HTM)-free carbon-based PVSCs with the structure of ITO/ETL/MAPbI 3 /carbon, the SnO 2 doped by TBAOH-Ti 3 C 2 T x (SnO 2:TBAOH-Ti 3 C 2 T x ) as ETL shows decreased WF and increased conductivity and improves the growth of the perovskite film with a larger grain and significantly reduced defects, which synergistically facilitate charge transport and extraction and reduce charge recombination. The HTM-free carbon-based PVSC with SnO 2:TBAOH-Ti 3 C 2 T x ETL exhibits a significantly higher PCE of 14.93% with enhanced device stability compared to the control device with pristine SnO 2 ETL (11.95%) and also outperforms most of the HTM-free carbon-based PVSCs with MAPbI 3 perovskite reported so far. In traditional inverted PVSCs with the structure of ITO/PTAA/MAPbI 3 /PCBM/CBL/Ag, the TBAOH-Ti 3 C 2 T x is utilized as a CBL to significantly enhance device performance with a high PCE of 21.16%, which is obviously superior than that (16.26%) of the control device without CBL. The impressive results indicate that tetrabutylammonium hydroxide-functionalized Ti 3 C 2 T x MXene possesses great application potential in different functional layers for high-performance PVSCs.