Interface Modification of a Perovskite/Hole Transport Layer with Tetraphenyldibenzoperiflanthene for Highly Efficient and Stable Solar Cells

Interface engineering has been recognized as a very effective method to simultaneously improve both efficiency and stability in perovskite solar cells (PSCs). In this work, we report using an excellent small molecular material tetraphenyldibenzoperiflanthene (DBP) to modify the perovskite/Spiro-OMeTAD interface to achieve significantly improved solar cell performance. It is found that the ultrathin DBP interlayer accelerates hole transfer across the FAxMA1–xPbInBr3–n/Spiro-OMeTAD interface and effectively reduces the nonradiative recombination. The Kelvin probe force microscopy and energy band analyses reveal that the DBP modification helps build better matched energy level alignment and smaller energy loss for more fluent hole transport. Consequently, the DBP-treated PSCs achieve an enhanced open-circuit voltage as high as 1.184 V and fill factor as high as 78.2% as well as the negligible hysteresis. The champion PSC made with DBP gives a PCE of 21.49%, significantly increased compared to 19.68% from the reference cell without the modification. Moreover, DBP also serves as a water-resistant protection for improved moisture stability. The PCE of the DBP-treated cells without encapsulation remains more than 84% of its initial efficiency, which is significantly higher than that of the reference PSCs (65%) after 20 days of storage under an air environment with 50–65% humidity. This study provides an effective interface modification material to address notorious stability problems in Spiro-OMeTAD-based PSCs.