Efficient hysteresis-less bilayer type CH₃NH₃PbI₃ perovskite hybrid solar cells

Bilayer type CH₃NH₃PbI₃ (MAPbI₃) perovskite hybrid solar cells were fabricated via a one-step spin-coating process by using solubility controlled MAPbI₃ solutions of MAPbI₃-DMSO (dimethyl sulfoxide) and MAPbI₃-DMF (N, N-dimethylformamide)-HI. The best DMSO-bilayer device showed 1.07 ±0.02 V V _oc (open-circuit voltage), 20.2 ±0.1 mA cm^-2 J _sc (short-circuit current density), 68 ±2% FF (fill factor), and 15.2 ±0.3% η (overall power conversion efficiency) under the forward scan direction and 1.07 ±0.02 V V _oc, 20.4 ±0.1 mA cm^-2 J _sc, 70 ±3% FF, and 15.9 ±0.4% η under the reverse scan direction. The best HI-bilayer device had 1.08 ±0.02 V V _oc, 20.6 ±0.1 mA cm^-2 J _sc, 75 ±1% FF, and 17.2 ±0.2% η under the forward scan direction and 1.08 ±0.02 V V _oc, 20.6 ±0.1 mA cm^-2 J _sc, 76 ±2% FF, and 17.4 ±0.3% η under the reverse scan direction. The deviation of average device efficiency ( of 20 DMSO samples and 20 HI samples was 14.2 ±0.95% and 16.2 ±0.85%, respectively. Therefore, the HI-bilayer devices exhibited better device efficiency and smaller J-V (current density-voltage) hysteresis with respect to the scan direction than the DMSO-bilayer devices due to the reduced recombination and traps by the formation of a purer and larger MAPbI₃ perovskite crystalline film.