A comparative study of solution-processed low- and high-band-gap chalcopyrite thin-film solar cells

Low-cost and printable chalcopyrite thin-film solar cells were fabricated by a precursor solution-based coating method with a multi-step heat-treatment process (oxidation, sulfurization, and selenization). The high-band-gap (1.57 eV) Cu(In_xGa_1-x)S₂ (CIGS) solar cell showed a high open-circuit voltage of 787 mV, whereas the low-band-gap (1.12 eV) Cu(In_xGa_1-x)(S_1-ySe_y)₂ (CIGSSe) cell exhibited a high short-circuit current density of 32.6 mA cm ^-2. The energy conversion efficiencies were 8.28% for CIGS and 8.81% for CIGSSe under standard irradiation conditions. Despite similar efficiencies, the two samples showed notable differences in grain size, surface morphology, and interfacial properties. Low-temperature transport and admittance characteristics of the samples clearly revealed how their structural differences influenced their photovoltaic and electrical properties. Such analyses provide insight into the enhanced solar cell performance of the solution-processed chalcopyrite thin films.