Improved performance and stability of perovskite solar cells by incorporating gamma-aminobutyric acid in CH3NH3PbI3Electronic supplementary information (ESI) available. See DOI: 10.1039/c8ta00948a

Organic-inorganic hybrid perovskites have attracted enormous attention due to their remarkable properties for high-efficiency solar cells in recent years. However, controlling the morphology of perovskite films is still a challenge using a solution synthesis method. Perovskite films with incomplete coverage are inevitable and this significantly limits the device photoelectric performance and long-term stability. In this work, we have combined gamma-aminobutyric acid iodide (GABAI) and CH 3 NH 3 I (MAI) as a mixed amine source in a precursor solution to fabricate a mixed-cation perovskite (GABA) x MA 1− x PbI 3 . As a result, high quality (GABA) x MA 1− x PbI 3 crystals were synthesized and showed better pore-filling and more complete contact with the TiO 2 scaffold, enhancing the power conversion efficiency from 15.08 to 18.31% with respect to the controlled MAPbI 3 solar cells. Importantly, the devices that contained GABA + also showed much higher stability when compared to the reference MAPbI 3 devices. This new chemical modification design, using bifunctional mixed cations in organic-inorganic hybrid perovskites, provides an efficient approach for improving both the performance and stability simultaneously. The partial substitution of methylamine (MA) with gamma-aminobutyric acid (GABA) in MAPbI 3 greatly improved the photovoltaic performance and moisture stability.