Tuning The Optical Properties Of Semiconductor Cu-In-Ga-S Colloidal Quantum Dots For Photoelectrochemical Applications

The unique optical properties of semiconductor quantum dots are reflected in the advantages of tunable size/composition,large Stokes shift,stable luminescence properties and high quantum yield,and have a broad absorption from visible light to infrared spectrum.The range and bright narrow-band emission properties enable low-cost,high-performance quantum dot-sensitized photoelectrochemical(PEC)Cells for hydrogen production.At the same time,in order to optimize the performance of PEC devices,the enhancement of light absorption and the improvement of carrier separation efficiency of the photoanode system are two crucial aspects.In order to achieve better photoelectric hydrogen production performance and physicochemical stability,it is necessary to rationally design quantum dot photosensitizers and control the mesoporous titanium dioxide(TiO₂)carrier transport layer.The specific research contents are as follows:1.Based on multi-component Cu In Ga S₂(CIGS)colloidal quantum dots,CIGS quantum dots were synthesized by a simple thermal injection method,and the effect of molar ratios of In:Ga elements on optical properties was studied.Then,by changing the synthesis temperature and time,the effect of different particle sizes on optical properties were studied.Based on the above work,the widening and narrowing of the energy band gap of CIGS quantum dots is realized.After further sensitizing the TiO₂carrier transport layer,the performance of PEC Cells as a photoanode was investigated.2.Application of CIGS quantum dots-based photosensitization effect in PEC Cells for hydrogen production.Due to the relatively large specific surface area of semiconductor colloidal quantum dots,most of the atoms will be concentrated on the surface of the quantum dots,resulting in many unsaturated bonds and suspended bonds on the surface.In order to solve the problem of surface defects of quantum dots,the core-shell quantum dots coated with Cd S shell comodified TiO₂ photoanode system was prepared by thermal injection method,which enriched the luminescence mechanism of CIGS QDS,and finally realized the saturation current density of?6.5 m A/cm~2.It is fully demonstrated that passivation of CIGS quantum dots through a suitable shell layer can achieve better performance and stability.3.Based on the Local surface plasmon resonance(LSPR)effect and carrier transport characteristics of noble metal,Au nanoparticles are used as the key to regulate the properties.Au nanoparticles and CIGS quantum dots were co-loaded in the mesoporous TiO₂ thin film layer to construct a CIGS-Au-TiO₂ photoanode system,so as to explain the synergy and correlation between optical properties and photoelectrochemistry.The optical properties and photocatalytic hydrogen production performance of the composite electrode were further optimized,and finally the saturation current density of?6.2m A/cm~2was achieved.Combined with the finite difference time domain(FDTD)method to simulate the local electromagnetic field distribution of plasma resonance,its mechanism is studied.All in all,these properties of the Au NPs attributed to facilitate charge separation and improve electron injection efficiency,as well as an interesting synergistic effect combined with the CIGS QDs enhance light absorption in the visible range,provides an effective strategy to realize an efficient PEC system for hydrogen generation.