Accurate Performance Characterization, Reporting, and Benchmarking for Indoor Photovoltaics
Indoor photovoltaics (IPVs) provide a promising solution for powering Internet-of-Things smart devices, which has led to a surge in IPV research. However, the diverse lighting scenarios adopted in IPV studies pose unique challenges in characterization, reporting, and benchmarking, which may obscure genuine performance improvements and result in inaccurate conclusions due to characterization errors. This study provides a comprehensive, quantitative analysis of these challenges, investigating them through the experimental characterization of IPVs covering a broad performance parameter space, including c-Si, a-Si:H, perovskite, and organic devices. We reveal that many of these challenges can lead to unacceptable error levels in IPV performance parameters, with the angular interplay among the test light source, measuring device, and IPV being particularly detrimental under diffuse indoor illumination. To address these characterization challenges, we evaluate practical protocols to mitigate them. We additionally analyze different benchmarking protocols, revealing the strengths of the reference-cell method and the limitations and solutions related to the indoor spectral coincidence concept. To facilitate the implementation of these findings, we provide comprehensive characterization, reporting, and benchmarking checklists. By enabling reliable performance evaluation and benchmarking, we anticipate that our analyses and guidelines will stimulate further advancements in IPVs, facilitating the realization of their full potential.