Quantum dot-based tandem photodiodes forhigh-efficiency photo-stimulation in biomedicalapplications

Photovoltaic retinal prostheses offer a promising solution for restoring vision in indi- viduals with degenerative retinal diseases through light-mediated neural stimulation. Colloidal quantum dots (QDs), particularly silver bismuth sulfide (AgBiS2 ), provide advantages for bioelectronic interfaces due to their high NIR absorption, chemical stability, and non-toxicity. Tandem photovoltaic structures are known to enhance performance by increasing the open-circuit voltage (Voc). We introduce a novel QD-based tandem photodiode, featuring ultra-thin AgBiS2 layers in both subcells. The device generates capacitive photocurrent, and due to the higher Voc, it in- jects higher ionic charge compared to non-tandem counterparts. The biointerfaces demonstrate low in vitro toxicity and stable photoelectrical performance under vari- ous tests. These results highlight the potential of this QD-based tandem photodiode as a high-resolution, efficient, and safe platform for retinal stimulation, offering a flexible, scalable solution for bioelectronic interfaces.