Composition Related Tunability of “Green” Core/Shell Quantum Dots for Photovoltaic Applications from First Principles

Quantum dots (QDs) with core/shell (c/s) type configurations are promising candidates for photovoltaic (PV) applications, as they known to enhance the QD stability, and also expected reduce charge carrier recombination both by reducing trap states increasing separation. Hence, here we report detailed first-principles studies of different compositions c/s QDs made from nontoxic materials, namely, CuInSe2/ZnS, CuInSe2/ZnSe, CuInSe2/CuInS2 their inverts, ZnS/CuInSe2, ZnSe/CuInSe2, CuInS2/CuInSe2. The geometric electronic properties studied using density functional theory (DFT). optimized structures all were found have a defect-free interface, which would charge-carrier rates arising due trapping. projected (PDOS) shows that highest occupied molecular orbital (HOMO) is mainly composed either S or Se states, whereas Zn In constitute lowest unoccupied (LUMO). Time-dependent DFT (TDDFT) calculations optical transitions show these systems strong absorption in visible region spectrum. Interestingly, configuration enables tailoring compared bulk well systems; QDs, relative thickness material composition core shell tunable parameter, addition size. A natural transition (NTO) analysis transfer upon light shows, surprisingly, separation occurs only certain configurations, such CuInSe2/ZnS QD, via fast direct electron shell, CuInSe2/ZnSe indirect transfer, may be slower. exhibit better efficiencies PV applications. Thus, our study highlights importance NTO giving insight into local excitations systems.