Semi-transparent solar cells for photovoltaic windows: A review of materials, performance optimization, and design challenges

The continuous growth in building energy consumption has intensified the demand for sustainable energy solutions, driving rapid advancements in building-integrated photovoltaics. Photovoltaic windows, as a multifunctional technology capable of simultaneously enabling electricity generation, natural daylighting, and thermal management, have emerged as a critical pathway for improving building energy efficiency. This review begins by introducing common strategies for enhancing light transmittance in the transition from traditional opaque solar cells to semi-transparent devices, and analyzes key factors influencing their performance improvement. It then provides a detailed assessment of six mainstream semi-transparent solar cell technologies—including amorphous silicon, cadmium telluride, copper indium gallium selenide, dye-sensitized, perovskite, and organic solar cells—with a focus on their device architectures and corresponding performance optimization methods. Notably, perovskite and organic solar cells have achieved remarkable breakthroughs in the synergistic optimization of visible light transmittance and power conversion efficiency, demonstrating considerable application potential. Furthermore, the review discusses critical challenges that must be addressed to facilitate the transition from laboratory research to large-scale commercialization, such as scalable fabrication, stability, cost, and environmental sustainability, and proposes promising solutions. This review aims to provide a systematic reference for the future development of photovoltaic window technology and to offer both theoretical support and practical insights for advancing building energy efficiency and green sustainable development.