Study On Preparation And Characterization Of CZTS Based Materials And Related Photodetectors

Copper-zinc-tin-sulfur(CZTS)based materials are rich in constituent elements,non-toxic,appropriate bandgap(1.5 eV)and high absorption coefficient(?104 cm-1),which are widely used to prepare green and low-cost optoelectronic devices.Although the research on CZTS-based solar cells has been made great breakthroughs,till now,there are only few reports on CZTS-based photodetectors.To further study CZTS materials and their photodetectors,the following work has been carried out:(1)CZTS(Se)thin films were prepared using a single-target magnetron sputtering followed by a post-heat treatment process.By optimizing the process parameters,the film,with a single phase of kesterite structure,suitable bandgap(1.51 eV and 1.11 eV,respectively)as well as smooth and dense surface morphology,was obtained after sulfuration(CZTS)or selenization(CZTSe)at 500 ?.(2)A CZTS nanocrystalline ink with a single dispersion and an average particle size of 10.48 nm was synthesized using a water-based solution method.A CZTS thin film was prepared by a spin-coating process,and the crystallinity was significantly improved when the CZTS films was annealed at 500 ?.however,it also turned out to have a small amount of SnS2 precipitation,larger bandgap and increasement of roughness when the CZTS films was annealed at 500 ?.(3)The CZTS/n-Si heterojunction photodetectors with a good photovoltaic effect from visible to NIR region under the excitation wavelength at 450,635 and 980 nm,respectively,have been made.The heterojunction photodetectors have a current switching ratio larger than pure n-Si and pure CZTS devices.The best response was obtained:the switching ratio is 314.23,the responsivity is 21.17 A/W,and the rise and fall time are 1.10 and 14.58 ms,respectively,at a 635 nm laser source(3 mW/cm2)when the thickness of the CZTS layer is 400 nm.(4)CZTS/graphene hybrid photodetectors were proposed for the first time.Comparing with pure CZTS detectors,it was found that the addition of graphene decreased the response time and increased responsivity by 5 times and 8000 times,respectively.The film annealed at 500 °C has a high responsivity of 312 A/W at 8 V bias,and under a 635 nm laser source(318.5 mW/cm2),which is much higher than the responsivity of the CZTS photodetector in reported previously.In conclusion,this study provides a new idea for the development of green low-cost CZTS materials and related photodetectors.