Tetrabutylammonium Hydroxide-Functionalized TiCT MXene for Significantly Improving the Photovoltaic Performance of Perovskite Solar Cells.

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 TiCT MXene (TBAOH-TiCT) is developed to improve the photovoltaic performance of PVSCs. TBAOH-TiCT is synthesized by HF etching and then TBAOH intercalation, and TBAOH can effectively attach to the TiCT surface during the intercalation process. In hole transport material (HTM)-free carbon-based PVSCs with the structure of ITO/ETL/MAPbI/carbon, the SnO doped by TBAOH-TiCT (SnO:TBAOH-TiCT) 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:TBAOH-TiCT ETL exhibits a significantly higher PCE of 14.93% with enhanced device stability compared to the control device with pristine SnO ETL (11.95%) and also outperforms most of the HTM-free carbon-based PVSCs with MAPbI perovskite reported so far. In traditional inverted PVSCs with the structure of ITO/PTAA/MAPbI/PCBM/CBL/Ag, the TBAOH-TiCT 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 TiCT MXene possesses great application potential in different functional layers for high-performance PVSCs.