Fraunhofer ISE Develops Indoor Solar Cells with Over 40 Percent Efficiency

In a major leap for smart energy solutions, researchers at the Fraunhofer Institute for Solar Energy Systems ISE have developed indoor photovoltaic (PV) cells that deliver more than 40 percent efficiency, a record-breaking achievement in low-light environments.

Built using gallium indium phosphide (GaInP), a III-V semiconductor, the new solar cells are finely tuned to convert weak indoor light, as low as 100 lux, into electricity with astonishing efficiency. This innovation opens new doors for powering indoor Internet of Things (IoT) devices that require energy autonomy without wired connections.

Dr. Henning Helmers, Head of Department at Fraunhofer ISE, emphasised the breakthrough’s potential, saying, “Various photovoltaic technologies exist for indoor use, but III-V semiconductor, especially under LED lighting, deliver the highest efficiencies.”

The study, published in Applied Physics Letters, showcased that n-doped GaInP cells significantly outperformed their p-doped counterparts due to longer charge carrier lifetimes. “This allows more electricity generation even under weak light,” explained lead author Malte Klitzke. “Our optimised cell architecture has proven exceptionally effective for indoor conditions," he noted.

The development is the result of a synergy of multiple projects including '50Percent” backed by Germany’s Federal Ministry for Economic Affairs and Climate Protection (BMWK), 'H2Demo” supported by the Ministry of Education and Research (BMBF), and 'SMART,' funded by AZUR SPACE Solar Power and the German Aerospace Center (DLR).

With a glowing red hue under laser excitation, the GaInP cell not only signals exceptional material quality but also a bright future for wire-free smart tech powered by ambient light.