Semitransparent Photovoltaics via Reflection Optical Paths.

Semitransparent photovoltaics (STPV) show great potential for building integration, but the imbalance between visible light transmission and power generation limits their practical applications. To overcome this, a reflective STPV (R-STPV) structure is proposed, via utilizing a dual-surface reflection optical path to achieve equivalent transmission. Unlike STPV systems relying on transmission optical paths, this design bypasses reflection losses and alleviates the stringent selective absorption requirements for the active layer. Thus, such design enables the fabrication of wavelength-selective STPVs using various high-performance photovoltaic materials such as silicon, CIGS, and CdTe. As a proof-of-concept, an optical reflector is designed to selectively reflect visible light and transmit the invisible one, and by integrating it with the above PVs, we demonstrate high-performance R-STPV with appropriate optical geometry. Remarkably, the best Si-based R-STPV delivers a reliable efficiency of 14.4%, an average visible light transmittance of 92.2%, a record light utilization efficiency of 13.28% and an exceptional color rendering index of 99%. The versatility of R-STPV window technology makes it suitable for various building-integration application scenarios, and an average annual power generation of 69.8 kWh year m is obtained according to the simulation results. Therefore, this work paves a new path for high-performance solar windows that will contribute significantly to energy sustainability.