Activating Earth-Abundant Element-Based Colloidal Copper Chalcogenide Quantum Dots for Photodetector and Optoelectronic Synapse Applications

Colloidal copper chalcogenide-based CuAlS2 (CAS) quantum dots (QDs) composed of earth-abundant and benign elements are emerging building blocks for optoelectronic technologies. However, their potential applications in high-performance optoelectronic devices are still unexplored due to limited optical properties and poor charge transfer efficiency. Here, a new class of CAS/ZnSe QDs exhibiting decent visible light absorption/emission was prepared and associative QD-gold nanoclusters (Au NCs) heterostructures were rationally constructed for improved charge separation and transport efficiency. Both experimental and theoretical studies revealed that such metal nanocluster decoration enables effective charge transfer from QDs to Au NCs. Photodetectors (PDs) fabricated using CAS/ZnSe QDs and Au-QD heterostructures were further demonstrated, wherein the Au-QDs PD show enhanced device performance with a responsivity of 7.57 A W-1 and a detectivity of 2.48 x 1011 Jones (405 nm, 2.8 mW cm-2) compared to that of the CAS/ZnSe QD PDs. We found that the Au NCs conjunction is key to setting intermediate energy levels and facilitating photoinduced charge transfer from QDs to the electron-transport layers (TiO2) employed in PD devices. Besides, as-assembled, Au-QD PDs have demonstrated optoelectronic synapse application by emulating the learning and forgetting processes under optical stimulation, representing a promising prototype device to achieve future solutionprocessed neuromorphic electronics.