Efficient all-air processed mixed cation carbon-based perovskite solar cells with ultra-high stability

Methylammonium lead iodide (MAPbI3) perovskite commonly used in hole-transport material (HTM)-free carbon-based perovskite solar cells (C-PSCs) is unstable in ambient conditions, and its glove box preparation process is essential but incompatible with the low-cost mass-production of C-PSCs. Although mixed cation/halide type perovskites are more durable against exposure to heat and moisture compared with a single cation MAPbI3 perovskite, the air-processed fabrication of stable mixed perovskite films out of the glove box has yet to be achieved in C-PSCs. We herein fabricate a multi-walled carbon nanotube (MWCNT)-incorporated FAxMA1−xPbIyBr3−y perovskite film in ambient air, in which hydrophobic MWCNTs are firstly introduced into the mixed perovskite matrix to mediate the crystallization of FAxMA1−xPbIyBr3−y and prevent the erosion by moisture of the perovskite layer. Based on the as-prepared MWCNT-incorporated FAxMA1−xPbIyBr3−y, the whole C-PSCs with the structure of ITO/SnO2/perovskite/C are constructed under actual ambient air conditions with low annealing temperature <150 °C, achieving outstanding power conversion efficiencies of 16.25% (0.08 cm2) and 12.34% (1 cm2). Particularly, the all-air-processed mixed cation C-PSCs maintain a long-term stability of 93% under ambient air conditions for 22 weeks, exhibiting the best ambient-air stability of PSCs fabricated in air so far. This study provides a feasible route for the commercialization development of low-cost, stable and efficient PSCs.