Perovskite solar cells (PSCs) have demonstrated high power conversion efficiencies and considerable potential for next-generation photovoltaic applications. However, their limited operational durability under environmental stress remains a major challenge for commercialization. Reliable lifetime estimation is therefore essential for evaluating their long-term performance under practical operating conditions. This study investigates the effects of temperature and illumination intensity on PSC durability and proposes an empirical approach for preliminary outdoor lifetime estimation based on controlled indoor measurements.

Encapsulated devices were subjected to maximum power point tracking (MPPT) under different temperature and LED illumination conditions for approximately 500 h. Five irradiance levels (20, 40, 60, 80, and 100 mW cm⁻²), calibrated using a silicon reference cell, were combined with four PSC temperatures (25, 55, 65, and 80 °C), resulting in 20 temperature–illumination combinations. The results revealed that efficiency retention generally decreased with increasing temperature and illumination, while the influence of illumination intensity was more pronounced at lower temperatures. At elevated temperatures, the absolute differences in efficiency retention among illumination conditions became smaller.

As the efficiency degradation exhibited a more consistent trend during the later stages of testing, the final 100 h (400–500 h) were selected for linear regression to investigate long-term degradation behavior. The slopes obtained under individual conditions showed relatively small variations, allowing their average to be adopted as a common degradation slope. An empirical model was then developed by expressing the fitted intercept as a function of temperature and illumination intensity, incorporating an Arrhenius-inspired temperature term and an illumination-dependent term.

The derived empirical equation was used to estimate T50 by incorporating annual average temperature and 24-hour average irradiance from representative regions. These preliminary estimates provide a basis for comparing PSC durability under different climate conditions. However, the model does not account for day–night variations or dark degradation and recovery, and further outdoor validation is required.

This work provides an empirical framework linking controlled indoor durability measurements with preliminary lifetime estimation, contributing to the assessment of PSC operational stability under different environmental conditions.