A highly stable hole-conductor-free CsxMA1-xPbI3 perovskite solar cell based on carbon counter electrode

Hole-conductor-free perovskite solar cells (PSCs) based on carbon counter electrode were fabricated under a high humidity air environment and the performance of Cs + doping in methylammonium lead iodide perovskite (Cs x MA 1- x PbI 3 ) as light absorber layer was investigated and discussed. After the doping of Cs + , the excellent morphology, crystallinity and light absorption of perovskite thin films were observed by corresponding test methods, leading to the higher short-circuit current density and open-circuit voltage in the relevant devices. However, excessive Cs + doping can damage the performance of PSCs. The optimized device with x  = 0.05, exhibited open-circuit voltage of 956 mV, short-circuit current density of 21.73 mA/cm 2 , fill factor of 0.509 and the power conversion efficiency ( PCE ) of 10.57% under AM 1.5G illumination showing a 16% enhancement than pure MAPbI 3 devices. The PSCs based on carbon counter electrode also showed high stability, despite being stored under ambient air without encapsulation. After 1000 h, the Cs 0.05 MA 0.95 PbI 3 devices maintained more than 90% of their initial PCE . The long-term stability can be attributed to the synergistic interaction of Cs + on the solid solution strengthening of MAPbI 3 and the protection of the hydrophobic carbon electrode on the perovskite active layer.