Tuning substrate temperature for enhanced vacuum-deposited wide-bandgap perovskite solar cells: insights from morphology, charge transport, and drift-diffusion simulations

Abstract

The e ciency of vacuum-processed perovskite solar cells lags behind that of solution-processed devices,partially because of the limited spectrum of deposition parameters that can be controlled during deposition.Substrate temperature is in principle a powerful tool to control the condensation and crystallization of thinlms, but has been scarcely investigated for perovskites. This study systematically investigates the e ect ofsubstrate temperature on the deposition of the wide-bandgap perovskite Cs0.2FA0.8Pb(I0.8Br0.2)3. Weobserve temperature-dependent morphological changes linked to variations in the adhesion coe cientof formamidinium iodide. Optical, structural, and optoelectronic analyses reveal that increasing thesubstrate temperature from−20 °C to 75 °C enhances charge carrier mobility and recombinationlifetime by an order of magnitude. However, these improvements do not directly translate into betterdevice performance due to competing factors such as morphology, interface energetics, and trapdensities. Using drift-di usion simulations, we identify key performance-limiting parameters, includingion mobility and charge trapping at interfaces and in the bulk. By optimizing the organic/inorganicdeposition rate at−20 °C, we achieve state-of-the-art e cient wide-bandgap perovskite solar cells withenhanced thermal stability. This study highlights substrate temperature as a crucial parameter forimproving material quality and device performance in vapor-deposited perovskites.