Ordering one-dimensional chains enables efficient selenium photovoltaics

As the world's first solid-state solar cells, selenium (Se) cells initiated contemporary photovoltaic research. However, the highest efficiency of Se photovoltaics has stagnated at 6.5% since 2017. Here, we report Se solar cells with a certified record efficiency of 7.2% through a critical melting-annealing strategy. This strategy provides enough energy to overcome the high activation energy of disordered Se chains and incorporate them into the lattice, arising from the unique one-dimensional crystal structure of photoactive trigonal Se. The resulting Se films exhibit a 2.3-fold reduction in trap density compared with conventional Se films. Such high-performance Se cells also achieve an efficiency of 18.0% under 1,000-lux indoor illumination, owing to their suitable wide band gap (∼1.9 eV) for indoor photovoltaics (IPVs). This efficiency surpasses those of market-dominant amorphous silicon and all currently available lead-free perovskite IPVs. We further construct Se IPV modules capable of generating a power of 559.8 μW, achieving self-powered wireless electronic shelf labels.