Preparation And Photoelectrochemical Water Splitting Performance Of Cu₂ZnSnS₄ Thin Films

Kesterite Cu₂ZnSnS₄?CZTS?absorbing materials have important applications in the thin film solar cells and solar water splitting cells due to their suitable bandgap?around 1.5 eV?,high light absorption coefficient(>10⁴ cm^-1),earth-abundant composition and low material cost.This article focuses on the main reasons that currently affect the photoelectrochemical performance of CZTS materials:the recombination of carriers at grain boundaries due to poor crystal quality of CZTS materials,and electron-hole recombination at composite interfaces of CZTS photocathodes obtained some research results.The specific research content is as follows:The CZTS thin film was prepared by a simple solution method using DMF as a solvent.We systematically studied the effect of heating rate,vulcanization temperature,sulfur powder addition amount,and CZTS thin film deposition substrate on the film growth during the high temperature vulcanization process.The results show that the grain growth is best when the curing temperature is 580°C and the added amount of sulfur powder is 400 mg,which can form a thin film with uniform surface and uniform grain size.Moreover,the conductive glass substrate containing fluorine-doped SnO₂ is more advantageous for the formation of large-grained CZTS thin films.The SnO₂ layer was inserted at different positions of the CZTS precursor film to obtain a high-quality CZTS film with no cracks,no holes,firm adhesion,and large grains running up and down.The effects of different insertion sites?upper,middle,and lower?of the SnO₂ layer on the morphology of the film were investigated.The results show that the introduction of the Sn-rich layer effectively inhibits the high temperature decomposition of the CZTS,and the insertion of the upper layer of the precursor film is more conducive to the formation of high-quality thin films without holes.The SnO₂ upper layer insert sample has a higher carrier concentration.As a photoelectrochemically decomposable water photocathode,its photocurrent density is 1.25 times higher than that of the blank sample without SnO2 insertion layer under the same conditions,showing a significantly improved photoelectrochemical performance.The Pt/TiO₂/In-OH-S/CdS/CZTS composite photocathode with further improved photocurrent and improved stability was sequentially modified on the surface of the Sn-rich CZTS photocathode.The results show that the introduction of the wide bandgap In-OH-S effectively suppresses the electron recombination at the interface between the CdS and the electrolyte,and increases the photocurrent nearly one time.The further introduction of the chemically stable TiO2 layer blocks the direct contact of the sulfide modifying layer with the electrolyte.While further improving the photocurrent(photocurrent is further increased 0.8times to 2.43 mA cm^-2),the stability of the photocathode is effectively improved,and showing excellent photoelectrochemical decomposition of water properties.