This simulation-based study uses SCAPS-1D to design and optimize silver sulfide (Ag₂S) solar cells in both bulk and quantum dot (QD) absorber configurations. Ag₂S, a low-cost and environmentally benign material, was investigated with absorber sizes ranging from bulk to 10 nm, 5 nm, 3 nm, and 2 nm QDs. Parameters for QDs smaller than 10 nm are extrapolated using quantum confinement theory and have not been experimentally confirmed; these simulations represent a theoretical exploration of extreme quantum confinement. This simulation-based study uses SCAPS-1D to design and optimize silver sulfide (Ag₂S) solar cells in both bulk and quantum dot (QD) absorber configurations. For QDs smaller than 10 nm, SCAPS-1D treats the absorber as a homogeneous effective medium and cannot explicitly model ligand chemistry, interdot tunneling, or energetic disorder. Therefore, results for 5 nm, 3 nm, and 2 nm QDs should be interpreted as hypothetical sensitivity analyses exploring quantum confinement trends, not as quantitative predictions for real devices. Within this framework, bulk Ag₂S and 10 nm QDs achieved the highest simulated efficiencies (16.60% and 16.86%, respectively), while smaller QDs exhibited higher built-in potentials and Voc due to quantum confinement but suffered from intensified recombination losses. These efficiency values are simulation results obtained using SCAPS-1D with effective-medium approximations for QD solids; they represent theoretical upper limits under idealized assumptions rather than predictions for existing experimental devices. Thickness optimization further highlighted distinct trends across device types. Bulk Ag₂S reached a maximum simulated efficiency of 23.65% at ~ 500 nm, whereas QD absorbers required much thinner layers: ~150 nm for 10 nm QDs, ~ 110 nm for 5 nm QDs, and only 21–30 nm for 3 nm and 2 nm QDs. Overall, these findings demonstrate that no single QD size is universally optimal; instead, high-performance Ag₂S solar cells demand careful balancing of absorber thickness, QD size, and interface engineering. This work provides theoretical insights for advancing Ag₂S-based photovoltaics as sustainable alternatives in next-generation solar technologies.
