Dynamic Solar Control and Energy Harvesting with Inorganic Photochromic Multilayers Smagul Karazhanov,¹ M. Srinithi,² I. Aulika,¹ S. Premkumar^2
1Institute of Solid State Physics, University of Latvia, LV-1063 Riga, Latvia
²Vellore Institute of Technology, 632014 Vellore, India.
e-mail address: smagul.karazhanov@cfi.lu.lv


This presentation provides a comprehensive investigation of all-inorganic multilayer coatings integrating photochromic layers, designed for dynamic solar energy conversion and management. In its bleached state, the photochromic layer absorbs approximately 10% of incident sunlight. However, upon ultraviolet excitation, it transitions to a photodarkened state with significantly enhanced absorption approaching 50% of the solar spectrum by absorbing photons of smaller energy as well. This functionality is complemented by transparent conductive oxide (TCO) layers, which reflect infrared radiation for passive cooling, and a photovoltaic component that converts absorbed sunlight into electricity while maintaining partial visible transparency.
We will present detailed results on the ultimate conversion efficiency and overall solar-cell performance for both the transparent and photodarkened states. Key challenges addressed include material degradation arising from both intrinsic mechanisms (e.g., native point defects, defect diffusion) and extrinsic environmental factors such as humidity as well as performance degradation. Furthermore, we discuss strategic approaches to control the bleaching kinetics, facilitating a reversible transition from the photodarkened to the bleached state. The optical response of the multilayer system is rationalized through a comprehensive model that accounts for the presence of intrinsic point defects and the coexistence of multiple phases within the photochromic layer. These findings offer new pathways toward self-powered, adaptive glazing for energy-efficient buildings and vehicles.

Photochromism, multilayer coating, adaptive solar control and solar energy harvesting