First-principles Study On The Photocatalytic Performance Of Type-Ⅱ Heterojunction Base On Ⅲ-Ⅵ Group

The production of renewable hydrogen from water through solar-driven photocatalytic water splitting reaction is regarded as an important way to solve growing environmental and energy problem.Janus of Ⅲ-Ⅵ group（M=In,Ga;X=S,Se）XM2Te are widely used in the field of photocatalysis and solar cells due to suitable band edge position,moderate band gap and excellent optical absorption.However,the single-layer XM2Te has limited separation ability and weak photoelectric conversion efficiency（PCE）,which greatly limits its practical applications as photocatalyst.It is reported that forming a type-II van der Waals（vd W）heterojunction is an promsing method to effectively improve electron-hole separation and PCE.Here,we use the first-principles calculation within HSE06 functional to study its photocatalytic performance of vd W heterojunction based on XM₂Te.The content of this article is as follows:（1）We construct layered vd W heterojunctions based on XM₂Te（M=In,Ga;X=S,Se）.Based on first principles energy calculations,we find that the Te-Te interface of AB stacking is the most stable stacking type.The band structures show that the SIn₂Te/Teln₂Se heterojunction has a 1.50 e V of direct band gap.And band edge position is suitable for water splitting.It is a typical type-II semiconductor,which can effectively reduce the recombination of electron-hole pairs.Moreover,the SIn₂Te/TeIn₂Se heterojunction possess wider light absorption spectrum and higher light absorption coefficient(～5x10⁴cm^-1)than its isolated Janus.The PCE of SIn₂Te/Teln₂Se heterojunction is up to 20.6%in the visible light range.The excellent photoelectronic performance indicates that the SIn₂Te/Teln₂Se heterojunction is a very potential photocatalytic hydrolysis catalyst.（2）The effects of strain on the photocatalytic performance is investigate.The results show that when the layer spacing is between 2.80A to 4.00A,the heterojunction always maintains direct band gap and type-II band arrangement.And the band edge position is still suitable for water-spliting,light absorption keeps robust and the PCE of the heterojunction reaches 21%.On the other hand,the excellent photocatalytic performance of the SIn₂Te/TeIn₂Se heterojunction can be well maintained under the in-plane from-1.00% to 1.50%.（3）The SIn₂Te/TeIn₂Se heterojunction is also an outstanding candidate for solar cell.We further study the influence of the external electric field on the photoelectric performance of the heterojunction.We find that the heterojunction still maintains excellent solar energy collection ability and stable electronic structure under positive electric field,which indicates that SIn₂Te/TeIn₂Se heterojunction is not only a outstanding photocatalyst for water splitting,but also a photovoltaic cell with stable performance.