Efficient hysteresis-less bilayer type CH3NH3PbI3 perovskite hybrid solar cells

Bilayer type CH3NH3PbI3 (MAPbI(3)) perovskite hybrid solar cells were fabricated via a one-step spin-coating process by using solubility controlled MAPbI3 solutions of MAPbI(3)-DMSO (dimethyl sulfoxide) and MAPbI(3)-DMF (N, N-dimethylformamide)-HI. The best DMSO-bilayer device showed 1.07 +/- 0.02 V Voc (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%. (overall power conversion efficiency) under the forward scan direction and 1.07 +/- 0.02 V Voc, 20.4 +/- 0.1 mA cm-2 Jsc, 70 +/- 3% FF, and 15.9 +/- 0.4%. under the reverse scan direction. The best HI-bilayer device had 1.08 +/- 0.02 V Voc, 20.6 +/- 0.1 mA cm-2 Jsc, 75 +/- 1% FF, and 17.2 +/- 0.2%. under the forward scan direction and 1.08 +/- 0.02 V Voc, 20.6 +/- 0.1 mA cm-2 Jsc, 76 +/- 2% FF, and 17.4 +/- 0.3%. under the reverse scan direction. The deviation of average device efficiency (havg) 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.