Optoelectronic Quality and Stability of Hybrid Perovskites Determined by Steady-State Luminescence Techniques

Abstract

Hybrid perovskites are the most promising solution-processable semiconductor for low-cost, high efficiency photovoltaic applications to date. In particular, inorganic-organic lead halide perovskites are well suited for converting the sun's rays into electrical power. In addition to having the right light-absorbing and charge-carrier transport properties, hybrid perovskites may be synthesized via facile solution-based deposition techniques and demonstrate notably low amounts of heat-generating losses under illumination. Even polycrystalline films cast from hand-made inks can sustain very high concentrations of light-generated charge carriers, and in turn sustain large open-circuit voltages. Further, the three-component formula of ABX3 (A = monovalent cation, B = divalent metal, C = halide) makes the composition space for hybrid perovskites enormous. Each component can be alloyed to tune the bandgap for either single-junction or two-junction applications. In this dissertation, several methods centered around steady-state photoluminescence are detailed for characterizing this new class of materials. We explore the impact of composition, illumination time, charge-injection, and atmospheric conditions on the optoelectronic quality and stability of hybrid perovskites. We show that absolute intensity steady-state photoluminescence measurements of neat hybrid perovskite thin-films modeled with the Lasher-Stern-Würfel equation enables reliable prediction of device open-circuit voltages. Combinatorial spray coating and photoluminescence mapping of halide alloys reveals that the optoelectronic quality decreases with increasing bromide concentration. Finally, we present a scalable analysis tool-kit to analyze wide-field microscope videos of hybrid perovskite thin-film photoluminescence flickering.