Periscope-Inspired Solar Windows Achieve Record 92% Transparency While Generating Electricity

Key Takeaways

• Reflection-mode design redirects visible light, avoids absorber losses
• Achieves 92.2% visible transmittance, 8.27% efficiency
• Light‑utilization efficiency reaches 7.62%, highest reported
• Optimal at 45° incidence; louver systems improve performance
• Stability: 80% efficiency retained after 50 h at 85 °C

Pulse Analysis

Transparent photovoltaics have long wrestled with the trade‑off between daylight transmission and electricity generation. Architects and engineers quantify this balance with light‑utilization efficiency, which multiplies power‑conversion efficiency by visible transmittance. Conventional transmission‑mode cells force photons through multiple layers, causing cumulative absorption that caps LUE around six percent. The periscope‑inspired approach sidesteps this bottleneck by reflecting visible wavelengths at the surface, allowing only near‑infrared light to reach the high‑performance organic absorber. This spectral segregation dramatically reduces parasitic losses and pushes LUE toward the theoretical ceiling.

The new reflection‑mode device employs a multilayer A‑layer reflector composed of tellurium dioxide and magnesium fluoride, engineered to bounce more than 95% of visible light while transmitting 96% of near‑infrared photons. Coupled with an opaque blend of PM6, BTP‑eC9, and L8‑BO, the cell achieves 8.27% power conversion and 92.2% average visible transmittance, yielding a record 7.62% LUE. Unlike prior semi‑transparent designs, the active layer remains untouched by visible photons, allowing the use of opaque, high‑efficiency materials without sacrificing clarity. Optical simulations confirm the dual‑mirror geometry performs best at a 45° incidence angle, where the periscope effect is maximized.

For real‑world deployment, angle‑dependent performance suggests integrating these panels into louver‑like or tilting façade systems that maintain optimal incidence throughout the day. The reported color‑rendering index of 89.1 ensures natural interior lighting, while accelerated aging tests show 80% efficiency retention after 50 hours at 85 °C, indicating reasonable durability for commercial windows. As glass‑covered skyscrapers dominate skylines, embedding such high‑transparency, power‑generating windows could offset a substantial portion of building energy demand, opening new revenue streams for developers and accelerating the transition to net‑zero architecture.