Solution processed Cu2S/TiO2 heterojunction for visible-near infrared photodetector

Abstract

A new method has been developed to grow copper (I) sulfide (Cu2S) nanoparticle (NP) inside a titanium dioxide (TiO2) thin film. This Cu2S NP growth process consists of two successive steps: ion-exchange and sulfurization process. In the beginning, Li4Ti5O12 thin film has been fabricated by a sol-gel process that contains mobile lithium-ion (Li+). This ion-conducting Li4Ti5O12 thin film has been deposited by spin coating and subsequent annealing method. In the following step, Li+ has been exchanged with Cu+ by the ion-exchange method that has been converted to Cu2S by subsequent sulfurization process. The ion-exchange has been done by immersing this Li4Ti5O12 thin film into a copper (I) chloride (CuCl) solution, whereas sulfurization has been done by dipping the Cu+ contain thin film within aqueous sodium sulfide (Na2S) solution. This process allows us to fabricate smooth and large area TiO2 thin film containing Cu2S NPs with an average particles of ∼10.5 nm. A lateral heterojunction photodetector has been fabricated based on this Cu2S-TiO2 thin film that shows a very good photoresponse in the visible-near infrared region with a highest detectivity of 1.7 × 1011jones at 830 nm. © 2020 Elsevier B.V.