Employing all-inorganic perovskite quantum dots (QDs) to treat organic-inorganic perovskite films has been well documented as a serviceable tactic to improve the performance of perovskite solar cells (PSCs). However, the inert molecule-coated QDs with zero-dimensional (0D) structure would limit further enhancement of the efficiency and stability of PSCs. Here, we employ a conductive diammonium porphyrin (ZnPy-NH3Br) to treat CsPbBr3 QDs coated on a three-dimensional perovskite film, thus constructing a stable 0D-two-dimensional perovskite capping layer. The generation of large-scale nanocube crystals by treating CsPbBr3 nanocrystallites with ZnPy-NH3Br in solution demonstrates such an assembly strategy. The formed capping layer can achieve efficient charge transport and separation. As a consequence, the best efficiency of an optimized device is up to 20.0%, which is superior to the control PSCs fabricated without modification (19.1%) and with pure CsPbBr3 QD modification (19.5%). More importantly, the porphyrin-treated CsPbBr3 QD-based devices retain over 65 or 85% of their initial efficiency when placed at 85 °C or 45% humidity tracking for 1000 h, respectively. Also, with the incorporation of QD-Por, the device retained 85% of the original efficiency when illuminated at AM 1.5 G for 450 h. Therefore, this work offered a facile avenue to modify perovskite films for fabricating highly efficient and stable PSCs.
Keywords: CsPbBr3 quantum dots; ligand exchange; perovskite solar cells; porphyrins; protective layer.