Modification of the Se/MoO Rear Interface for Efficient Wide-Band-Gap Trigonal Selenium Solar Cells

Trigonal selenium (t-Se) is a promising wide-band-gap photovoltaic material with a high absorption coefficient, abundant resources, simple composition, nontoxicity, and a low melting point, making it suitable for absorbers in advanced indoor and tandem photovoltaic applications. However, severe electrical losses at the rear interface of the t-Se absorber, caused by work function and lattice mismatches, limit the voltage output and overall performance. In this study, a strategy to enhance carrier transport and collection by modifying interfacial chemical interactions is proposed. By applying a controlled heat process during the deposition of the MoO hole transport layer, a chemical interaction at the t-Se/MoO interface can be facilitated. This results in the formation of an interfacial MoSe layer, leading to improved valence band alignment and reduced barrier and recombination losses. As a result, the performance of t-Se thin-film solar cells is improved compared to those without the heating process.