Smart photocapacitive Cu2SnS3 quantum dots-based flexible biointerface for retinal-inspired photoelectrical stimulation

Retinal degeneration, marked by the progressive loss of photoreceptors, is a leading cause of blindness. Photocapacitive biointerfaces provide a prosthesis-style approach to reestablish light-driven neural activity. Here, we present a flexible Cu₂SnS₃ quantum dots/polymer heterojunction (P3HT:PCBM)-based hybrid biointerface that enables wireless photoelectrical stimulation of neurons. The device is forming a stack whose effective capacitance and photocurrent scale with wavelength, emulating retinal spectral sensitivity. When interfaced with neurons, the heterojunction produces red-light-evoked photocurrents (peak ~4.5 nA at 8 mW cm⁻²) and drives measurable changes in both membrane potential and intracellular calcium (ΔF/F₀ increase of ~10%). The operation is non-thermal and remains in the capacitive regime, while the hybrid architecture enhances charge separation and interfacial storage compared with single-material layers. These results define a flexible photocapacitive platform that achieves visible/NIR neuromodulation. Validation on hippocampal neurons and future studies on retinal ganglion cells advance this platform toward prosthetic vision applications.