Engineering The Optoelectronic Properties Of Eco-friendly CuAlS₂/ZnSe Quantum Dots For Photodetectors And Optoelectronic Synaptic Applications

In the current digital age,the exponential growth of information presents a challenge for traditional information processing technologies.Artificial intelligence（AI）is considered one of the most efficient approaches for handling large data tasks.To achieve AI technologies,it is necessary to develop neuromorphic devices that highly simulate human brain.However,traditional all-electronic devices cannot meet the requirements of low energy consumption and high integration.In contrast,optoelectronic technology combining the photons and electrons possesses significant advantages of low energy consumption and high bandwidth,which renders its highly prospective for neuromorphic applications.Photodetectors（PD）are important basic components in optoelectronics,with the ability to convert,process,and store optical signals,and are expected to be used as artificial optoelectronic synapses to well mimic human nevous system.Recently,semiconductor colloidal quantum dots（CQD）with tunable optical/electrical properties have been widely used in the construction of PDs or optoelectronic synapse devices due to their solution processing and large-scale preparation characteristics.However,currently high-performance QD-based PDs typically contain toxic heavy metal Pb/Hg elements（e.g.,PbS,HgS）,and the low-toxicity alternatives of Ⅰ-Ⅲ-Ⅵ QDs are also based on rare metal elements such as In/Ga（e.g.,CuInS₂,CuGaS₂）,which hinder their practical applications in daily life.This thesis addresses these issues by designing and preparing an eco-friendly CuAlS₂/ZnSe core-shell QDs based on the earth-abundant element Al,and further utilized Au nanoclusters to modify the QD properties,and finally studied the related photodetection and synaptic properties of the prepared QD-PD.The main research contents of this thesis are as follows:（1）An eco-friendly CuAlS₂/ZnSe core-shell QDs was synthesized by a one-pot method,and the prepared-QDs showed excellent light absorption and emission characteristics in the UV-visible range.By combining the QD with mesoporous TiO₂ film,a type-II band structure photoactive layer with effective photo-induced carrier separation and transfer efficiency was formed.The PDs fabricated by the QD photoactive layer exhibited a responsivity of up to 3.53 A/W and a detectivity of 2.34×10¹¹ Jones at 405nm.（2）An Au-CuAlS₂/ZnSe QD heterojunction structure was constructed and decorated by Au nanoclusters.Experimental and theoretical studies demonstrated the efficient photo-generated electron transfer from QD to Au nanoclusters in the heterojunction structure.Compared with the CuAlS₂/ZnSe-PD,the prepared Au-QD-PD exhibited higher responsivity of 7.57 A/W as well as detectivity of 2.48×10¹¹ Jones at 405 nm,while this performance enhancement was mainly attributed to the intermediate energy level promoted by the Au nanoclusters,which facilitated the photo-induced electron transfer between QD and TiO₂.（3）Based on the response time characteristics of the Au-QD-PD,the related optoelectronic synaptic properties of this device were further studied.By simulating the typical characteristics of biological synapses and demonstrating image learning and forgetting processes under optical pulse stimulation,the benign optoelectronic synapse functional characteristics of this type of device were demonstrated,which is expected to be applied in the future low-cost,solution-processed preparation of neuromorphic optoelectronic technology.