<p>Photovoltaic devices are usually qualified at room temperature and standard illumination. However, actual operation conditions change significantly during a day or year, influencing cell performance—especially in tandem cells—yet, the temperature-dependence of optical parameters such as bandgap and absorption in PV materials is often overlooked. Understanding these effects, therefore, is essential for proper cell architecture optimization and accurate energy yield estimation. In this study, methylammonium-lead-triiodide (MAPbI₃) perovskite layers were fabricated using sequential PVD technique and compared to slot-die coated samples from industrial source, and their optical properties were measured using spectroscopic ellipsometry at temperatures from 25 to 65 °C. The layers featured temperature coefficients of approx. + 0.54 meV/°C for the optical bandgap, and − 0.1%/°C for the absorption coefficient in relevant wavelength ranges, consistent with previous estimations of temperature coefficients by I–V characteristics. Although generally present for all tested samples, the magnitude of these effects varied by fabrication process.</p> Graphical abstract <p></p>