CuBiSe2 Quantum Dots as Ecofriendly Photosensitizers for Solar Cells

Cu-based ternary chalcogenides have shown high promise as low-cost ecofriendly alternatives to heavy-metal based photosensitizers. The successive ionic layer adsorption and reaction (SILAR) processed CuBiSe2 quantum dots possess an optimal bandgap, appealing photoresponsivity (excellent absorption coefficient of (10)5 cm–1), and photostability. Because of these advantageous properties, they have been investigated as photoabsorber materials for solar cells in this work for the first time. Use of such nontoxic and nonscarce materials, paired with low-temperature solution processing can address both concerns of environmental regulation and fabrication costs. The performance of the prototype solar cell developed has been satisfactory as a new emerging material (power conversion efficiency (PCE) of 2%) unlike the reported CuBiS2 showing a PCE of 0.68%. A further increase in efficiency was observed with the formation of a heterostructure CuBiSe2/CuBiS2 that exhibits a type-1 heterostructure and enables improvement in power conversion efficiency up to 2.6%. CuBiS2 acts as a passivation layer (reducing surface defects and recombination losses) and also as an absorber, facilitating confinement and longer lifetime of charge careers. A detailed investigation of these Cu based selenium quantum dots and the insights provided into their electronic structure and dynamics in this work would significantly influence the future research of these materials into other optoelectronic applications.