Flexible InGaP/GaAs Tandem Solar Cells Encapsulated with Ultrathin Thermally Grown Silicon Dioxide as a Permanent Water Barrier and an Antireflection Coating

The lifetime and stability of flexible photovoltaic (PV) devices are crucial factors in the production of sustainable and eco-friendly energy. However, flexible PV devices are usually constructed with a thin active material integrated onto a soft substrate, the surfaces of which are prone to moisture and heat damage, making devices unreliable in terms of their lifetime and stability. Here, we built flexible InGaP/GaAs tandem solar cells with an ultrathin thermally grown silicon dioxide layer as a permanent water barrier and an antireflection coating (ARC). By transferring an ultrathin thermally grown silicon dioxide onto flexible InGaP/GaAs tandem solar cells, there was no performance degradation even after soaking the solar cells in water at 70 °C for 10 days. Furthermore, the energy conversion efficiency of the solar cell with a thermally grown silicon dioxide layer was improved by 2.24% due to antirefletion effect compared with that of the solar cells without the silicon dioxide layer. Such device technology establishes a stable energy source not only for vehicles, satellites, and drones exposed to harsh environments but also for underwater operating systems and sensors.