In Short : Fraunhofer ISE has developed indoor photovoltaic cells using gallium indium phosphide (GaInP) with over 40% efficiency under low-light conditions. These III-V cells achieve up to 41.4% efficiency at 1000 lux, making them ideal for powering indoor IoT devices. Their performance at just 100 lux remains strong, offering a sustainable, wireless energy solution for smart environments.
In Detail : Scientists at Fraunhofer ISE have developed advanced indoor photovoltaic cells using gallium indium phosphide (GaInP), achieving over 40% power conversion efficiency. This marks a significant breakthrough in solar technology for low-light indoor environments, where traditional silicon cells underperform.
These cells are based on III-V semiconductors, known for their superior electronic properties. The optimized GaInP absorber, featuring an n-doped double-heterostructure, was key to achieving such high efficiency levels under artificial light sources commonly found indoors.
The research demonstrated that the cells reach a record 41.4% efficiency under 1000 lux of LED illumination. Even at just 100 lux—typical of dim indoor conditions—the cells maintained an impressive 37.5% efficiency, showing their ability to operate effectively across a wide range of lighting levels.
This performance is attributed to the GaInP material’s optimal 1.9 eV bandgap, which aligns well with indoor light spectra, particularly from LEDs. The cells efficiently generate charge carriers and maintain high voltage and current even in low-irradiance environments.
A key finding in the study was the superior performance of n-doped cells over p-doped variants. The n-doped design allows for longer carrier lifetimes and better charge retention, leading to improved overall efficiency in low-light operation.
The development is part of several German research initiatives, including the ‘50Percent’, ‘SMART’, and ‘H2Demo’ projects. These programs aim to enhance the role of photovoltaics in next-generation energy systems, particularly for autonomous indoor applications.
Such high-efficiency indoor cells are particularly suited for powering Internet of Things (IoT) devices, sensors, and electronics in homes, offices, and industrial facilities. Their ability to function reliably without wired power connections could significantly enhance the autonomy of smart devices.
Fraunhofer’s achievement paves the way for more sustainable and maintenance-free energy solutions indoors. With the growing demand for wireless and compact energy sources, this innovation could transform how electronics are powered in the near future.
