Defect Quantification in Metal Halide Perovskites Anticipates Photoluminescence and Photovoltaic Performance
Michel De Keersmaecker, Juan Tirado, Neal R. Armstrong, Erin L. Ratcliff
Abstract
Semiconductor material optimization requires quantification of performance and stability-dependent near-valence maximum and near-conduction minimum defects with sufficient energy resolution and sensitivity. Herein, we utilize a spectroscopy-electrochemistry approach to resolve the energy-distinct donor and acceptor defect concentrations in wide-gap (Cs .05 FA .79 MA .16 )Pb(I .87 Br .13 ) 3 perovskites, benchmarked against photoluminescence and photovoltaic device performance. Monitoring charge transfer events to electron acceptor and donor molecules within solid electrolyte top contacts enables defect quantification below 10 15 cm –3 at an energy resolution of 10 meV under device-relevant bias, well below levels reported by other methods. Further method sensitivity is demonstrated for defects arising from <2% formamidinium concentration modifications, mimicking compositional imperfections resulting from nonoptimized processing. This method provides the first complete perovskite energetic diagrams with small changes in composition, is nondestructive, compatible with in-line processing characterization, and will enable the semiconductor community to link molecular origins of defects with limitations in device performance across a wide array of optoelectronic platforms.