Tailoring the structure and defects of non-toxic nanocrystalline Bi₂S₃solar cells

Solar cells can satisfy the increasing demand for energy worldwide, but the toxicity of semiconductors used in solar cells can overshadow their utility as a renewable source of energy. Bi₂S₃, with a desirable band gap of 1.3ev, and as a non-toxic n-type semiconductor can be a favorable replacement for toxic semiconductors containing Pb, Cd or Te. However, nanocrystalline Bi₂S₃films synthesized by various techniques such as successive ionic layer adsorption and reaction (SILAR) have not reached high solar energy conversion efficiencies hitherto, and have primarily been studied as sensitizers for photoelectrochemical applications. Here, we report the synthesis and characterization of non-toxic all-inorganic solid-state Bi₂S₃photovoltaic solar cells. We enhanced the solar energy conversion efficiency of the nanocrystalline Bi₂S₃solar cells by optimizing the structure of the electron and hole transport layers, and by tailored annealing treatments that modify the size of the Bi₂S₃nanocrystals and decrease their defect concentrations.