Superior Multiple Exciton Generation in Ecofriendly Ag₂Se Colloidal Quantum Dots

Multiple exciton generation (MEG) or carrier multiplication, which yields two electron-hole pairs or excitons from one absorbed high-energy photon, holds great promise to enhance the conversion efficiency of optoelectronic devices. Currently, the realization of efficient MEG largely relies on colloidal nanocrystals containing toxic heavy-metal elements, with eco-friendly and satisfactory forerunners remaining out of reach. Here, we report the superior MEG characteristics in low-toxicity Ag₂Se colloidal quantum dots (CQDs) with a low threshold commencing close to the energy conservation limit of twice the bandgap energy (∼2.26E_g) and a high conversion efficiency reaching up to ∼91% based on the standard model. Nonequilibrium dynamics suggest that, benefiting from the sparse density of states in Ag₂Se CQDs, efficient MEG prolongs the buildup of exciton populations and occurs via the inverse Auger process. Combined with the solution processability and an optimal bandgap close to 1 eV, Ag₂Se CQDs may serve as an excellent candidate for sustainable and flexible third-generation photovoltaics.