Markovian and non-Markovian measurements play a critical role in characterizing open quantum systems and elucidating phenomena associated with radiation absorption processes. Motivated by recent advances in solar radiation harvesting technologies, this work presents a theoretical and computational study of guanidinium-based perovskites with \(25\%\) substitution. Using ab initio-inspired modeling and open quantum system simulations, we examine the non-Markovian dynamics governing UV–Vis light–matter interactions in these materials. Our simulations reveal that electronic states at the surface of guanidinium perovskites suppress Pb–I hybridization and enhance the dielectric response, resulting in improved polarization and longer charge carrier lifetimes. Non-Markovian analyses further show that guanidinium cations promote low-energy vibrational modes and facilitate the formation of large polarons. Finally, we demonstrate that tuning spectroscopic parameters critically affects the manifestation of Markovian and non-Markovian features across a wide temperature range in these perovskite structures.
