Optoelectronic Quality and Stability of Hybrid Perovskites from MAPbI3 to MAPbI2Br Using Composition Spread Libraries

Abstract

The development of stable high-bandgap hybrid perovskites (HPs) with high optoelectronic quality may enable tandem solar cells with power conversion efficiencies approaching 30%. The halide composition of HPs has been observed to effect bandgap, carrier lifetime, and material stability. Here we report optoelectronic quality and stability under illumination of thousands of compositions ranging from the pure iodide (CH3NH3PbI3) to the diiodomonobromide (CH3NH3PbI2Br). Hyperspectral maps of steady-state absolute intensity photoluminescence (AIPL) are used to determine the quasi-Fermi level splitting (QFLS) at each point after synthesis. The QFLS upon first illumination increases with bandgap and reaches a maximum of 1.27 eV under 1 sun illumination intensity for a bandgap of 1.75 eV. However, the optoelectronic quality (χ), defined as the ratio of the QFLS to the maximum theoretical QFLS for bandgap, decreases with bandgap from around 88% for 1.60 eV bandgap down to 82% for 1.84 eV bandgap. Further, we show ...