Intensity Dependent Photoluminescence Imaging for In‐Line Quality Control of Perovskite Thin Film Processing

Large area fabrication of high-quality polycrystalline perovskite thin filmsremains one of the key challenges for the commercial readiness of perovskitephotovoltaic (PV). To enable high-throughput and high-yield processing,reliable and fast in-line characterization methods are required. The presentwork reports on a non-invasive characterization technique based onintensity-dependent photoluminescence (PL) imaging. The change in PLintensity as a function of excitation power density can be approximated by apower-law with exponent k, which is a useful quality indicator for theperovskite layer, providing information about the relative magnitudes ofradiative and non-radiative recombination. By evaluating k-parameter mapsinstead of more established PL intensity images, 2D information is obtainedthat is robust to optically induced artifacts such as intensity variations inexcitation and reflection. Application to various half stacks of a perovskitesolar cell showcase its ability to determine the importance of the interfacebetween the charge transporting and perovskite layers. In addition, thek-parameter correlates to the bulk passivation concentration, enabling rapidassessment of open-circuit voltage variations in the range of 20 mV.Considering expected improvements in data acquisition speed, the presentedk-imaging method will possibly be obtained in real-time, providing large-areaquality control in industrial-scale perovskite PV production.