Study on degradation mechanism of perovskite solar cell and their recovering effects by introducing CH3NH3I layers

Abstract We demonstrate the degradation mechanism of CH 3 NH 3 PbI 3 perovskite solar cells (PSCs) and their recovery effects by introduction of CH 3 NH 3 I layers. After degradation by exposure to air under a 1-sun condition for 18 h, the absorption of the CH 3 NH 3 PbI 3 perovskite between 530 and 800 nm decreases, and thereby the energy band gap increases. X-ray diffraction (XRD) patterns indicate that moisture with sunlight corrodes the CH 3 NH 3 PbI 3 perovskite into PbI 2 , which generates cracklike voids on the surface of illumination-degraded CH 3 NH 3 PbI 3 perovskite thin films. As a result, the PSC photovoltaic performance is degraded and the power conversion efficiency (PCE) is reduced from 16.8 to 0.7%. However, the PCE is recovered to 7.6% by spin-coating a CH 3 NH 3 I layer into the illumination-degraded CH 3 NH 3 PbI 3 perovskite thin films. The recovery of the absorption between 530 and 800 nm and the CH 3 NH 3 PbI 3 -perovskite-assigned peaks in the XRD patterns verifies that the illumination-induced PbI 2 is recombined with spin-coated CH 3 NH 3 I and that the CH 3 NH 3 PbI 3 perovskite structure is recrystallized.