A research team led by Prof. GAO Peng from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences has developed high-performance perovskite solar cells with enhanced environmental stability.

The team reported a 2-(4-fluorophenyl)ethylamine (FPEA: 4-FC6H4C2H4NH3) bulky cation to grow a 2D perovskite overlayer on the top of the Cs/FA/MA triple-cation 3D perovskite to combine the high stability of 2D perovskite with high efficiency of 3D perovskite simultaneously.

The density functional theory (DFT) calculations based on the defect model evaluated the slab surface energies of three kinds of perovskite crystals, the triple-cation mixed 3D perovskite, PEA2PbI4, and FPEA2PbI4, respectively. The defect formation energy of (FPEA)2PbI4 is much higher than that of (PEA)2PbI4, which will benefit to enhance the stability when it is deposited on top of a 3D perovskite.

By performing X-ray diffraction (XRD), photoluminescence (PL), and Laser Scanning Confocal Microscope (LSCM) experiments, the researchers confirmed the formation and distribution of (FPEA)2PbI4 crystals on top of the 3D perovskite.

Employing the 3D-2D perovskite as the absorbing layer in the photovoltaic cells, they realized a high power conversion efficiency of 20.54% with a higher VOC of 1.126 V, a JSC of 22.80 mA cm-2, and an FF of 0.80.

In addition, the researchers achieved a stabilized efficiency of 20.26% by introducing 2 mg mL-1 FPEAI/IPA solution onto the 3D perovskite films with greatly enhanced stability than the control cell sustaining 99% of their initial efficiency after 864 h.

Further study is underway in the lab exploring more hydrophobic aromatic fluorocarbons to improve the micromorphology of the perovskite layer and moisture- resistant properties of PSCs.