Light-induced degradation and self-healing inside CH3NH3PbI3-based solar cells

CH3NH3PbI3 (MAPbI(3))-based perovskite solar cells (PSCs) with special hole and electron transport layers (HTL and ETL) were prepared to study their light-induced degradation. Obvious degradation was observed under initial light exposure not only at the device level but also at the film morphology and electronic structure level. Device performance parameters, such as short-circuit current (J(SC)), power conversion efficiency, fill factor, and hysteresis effect, were aggravated with an initial light exposure of less than similar to 8 h at 1 sun intensity. Meanwhile, the deteriorated crystallinity and electronic structure of the MAPbI(3) film were also detected with x-ray diffraction, ultraviolet photoelectron spectroscopy, and UV-Visible absorption spectroscopy. The observed degradation is rationally related to the light-induced decomposition of MAPbI(3). However, the degradation can be partly recovered with the following light exposure resulting in self-healing of the devices and MAPbI(3) films. The self-healing behavior should be ascribed to the conversion of decomposition products back to MAPbI(3), because the intermediates are wrapped tightly in the photoactive layer by the compact coverlayers of HTLs and ETLs and some reversible reactions occur consequently. The mechanism of self-healing is discussed by introducing the trapped states derived from ion migration. The PSCs prepared here imply a good optical stability and thus a good performance facilitated by tight wrapping of the active MAPbI(3).