Low-cost and easily prepared interface layer towards efficient and negligible hysteresis perovskite solar cells

Matched energy level alignment and minimal non-radiative recombination at the buried perovskite/charge transport material interface are essential for efficient electron transfer and highly-efficient perovskite solar cells (PSCs). Herein, we develop a facile and feasible method by inserting Cesium(I) Bis(trifluoromethanesulfonyl)imide (CsTFSI) interlayer to fabricate high performance PSCs with negligible hysteresis. With CsTFSI modification, tin oxide displays less trap density, improved electrical conductivity and better energy level alignment with perovskite, leading to a considerable increase in power conversion efficiency (PCE). Consequently, the champion target device presents a PCE of 22.05%, much higher than that of the control device (19.93%). Our work provides an effective and simple strategy for the modification of perovskite buried interface to obtain highly efficient PSCs.