Exploring Cu-Doping for Performance Improvement in Sb₂Se₃ Photovoltaic Solar Cells

Copper-doped antimony selenide (Cu-doped Sb₂Se₃) thin films were deposited as absorber layers in photovoltaic solar cells using the low-temperature pulsed electron deposition (LT-PED) technique, starting from Sb₂Se₃ targets where part of the Sb was replaced with Cu. From a crystalline point of view, the best results were achieved for thin films with about Sb_1.75Cu_0.25Se₃ composition. In order to compare the results with those previously obtained on undoped thin films, Cu-doped Sb₂Se₃ films were deposited both on Mo- and Fluorine-doped Tin Oxide (FTO) substrates, which have different influences on the film crystallization and grain orientation. From the current-voltage analysis it was determined that the introduction of Cu in the Sb₂Se₃ absorber enhanced the open circuit voltage (V_OC) up to remarkable values higher than 500 mV, while the free carrier density became two orders of magnitude higher than in pure Sb₂Se₃-based solar cells.