Modeling Degradation Kinetics of FAPbI₃ Perovskite Solar Cells: Impact of Microstructural and Optoelectronic Defects

The operational thermal stability of perovskite solar cells (PSCs) is a critical issue hindering their commercialization. Therefore, besides achieving high power conversion efficiency (PCE), understanding and quantifying the device degradation kinetics of PSCs is necessary for their reliability and to prevent failure under thermal stress. In this work, exponential and linear degradation models have been adopted to comprehend and quantify the degradation kinetics of FAPbI3 and multifunctional fluorinated molecule 3-fluoro-4-methoxy-4’,4”-bis((4-vinyl benzyl ether) methyl)) triphenylamine (FTPA)-modified FAPbI3 PSCs. Further, various figures of merit, such as acceleration factor, degradation factor, mean lifetime, transformational fraction, and activation energy, have been deduced by fitting the PCE degradation data into the Arrhenius equation and onto the Johnson– Mehl-Avrami (JMA) kinetic models. These figures of merit have been correlated with other defect-determining factors such as micro-strain and Urbach’s energy. The degradation factor and PbI2 residuals are reduced for controlled PSCs to FTPA-modified PSCs. Furthermore, the activation energy and operational thermal stability of FTPA-modified PSCs have increased due to the forming of a hydrogen-bonding polymer network, which enhances PSCs’ thermal stability and acceleration factor. Our findings reveal that the studied devices’ intrinsic stability, thermal stability, and mean lifetime strongly correlate with micro-structural and optoelectronic defects, which helps to improve the performance of photovoltaics.