Towards Improved Device Performance: A Study on Defects and Interfaces in MHP Devices using Electron Spin Resonance Spectroscopy

Electron spin resonance (ESR) spectroscopy has been identified as a powerful method for nondestructively probing intrinsic defects and interfaces in metal halide perovskite (MHP) devices. Key challenges in MHP devices stem from defects originating from synthesis, interface reactions, lattice strain, energy level mismatches, and other interfacial issues. Furthermore, intrinsic perovskite defects, which tend to propagate post-device deployment [1–3], have substantial implications on device stability. Traditional approaches, like photoemission, often fall short in accurately characterizing these defects due to their constraints at near-surface regions. To circumvent these limitations, nondestructive methods with an acceptable probing depth and sensitivity are needed. In our study, UV and visible light sources were applied to MHP samples to analyze degradation dynamics. We acquired both ex situ and in situ EPR spectra from MHP single crystals, precursor powders, and perovskites interfaced with transport materials. The results provide valuable insights into defect origins and degradation pathways, further emphasizing the importance of a comprehensive understanding to improve MHP-based device longevity and performance.