Electrical engineering

Physics

Nanotechnology

Organic chemistry

Thermochromism

Phase transition

Engineering

Perovskite (structure)

Halide

Inorganic chemistry

Chemistry

Materials science

Iodide

Transparency (behavior)

Computer science

Photovoltaic system

Quantum mechanics

Computer security

Chemical engineering

Optoelectronics

Nature Materials

Smart photovoltaic windows represent a promising green technology featuring tunable transparency and electrical power generation under external stimuli to control the light transmission and manage the solar energy. Here, we demonstrate a thermochromic solar cell for smart photovoltaic window applications utilizing the structural phase transitions in inorganic halide perovskite caesium lead iodide/bromide. The solar cells undergo thermally-driven, moisture-mediated reversible transitions between a transparent non-perovskite phase (81.7% visible transparency) with low power output and a deeply coloured perovskite phase (35.4% visible transparency) with high power output. The inorganic perovskites exhibit tunable colours and transparencies, a peak device efficiency above 7%, and a phase transition temperature as low as 105 °C. We demonstrate excellent device stability over repeated phase transition cycles without colour fade or performance degradation. The photovoltaic windows showing both photoactivity and thermochromic features represent key stepping-stones for integration with buildings, automobiles, information displays, and potentially many other technologies. CsPbI3–xBrx solar cells, which undergo temperature- and moisture-driven reversible transitions between a non-perovskite transparent phase and a perovskite light-absorbing phase, are used as thermochromic photovoltaic devices integrated in windows.

Thermochromic halide perovskite solar cells