Design Of MoO₃ Array Back Interface And Its Effect On CZTSSe Solar Cell Performance

As a new type of inorganic thin film solar cell,Cu₂ZnSn（S,Se）₄（CZTSSe）solar cell has become an important research direction in the field of clean energy because of its abundant reserves of component elements,environmental friendliness,adjustable band gap range and high light absorption coefficient.At present,the maximum photoelectric conversion efficiency of this kind of cell in the laboratory can reach 13.6%,but it is still far from the Shockley-Queisser limit efficiency of 32%.Improving the efficiency of CZTSSe solar cells is still the core of the development of this field.In this paper,based on a brief review of the current research status of CZTSSe photovoltaic performance improvement at domestic and overseas and the existing problems,we systematically summarized the author’s research work on the electrical contact of the back electrode interface with the title of"Design of MoO₃ array back interface and its effect on CZTSSe solar cell performance".It mainly includes the following three aspects of research content and achievements:1.Carrier CZTSSe/MoSe₂ interface recombination caused by n-type MoSe₂ layer formed inevitably during the Se process of Cu₂ZnSnS₄ precursor thin film is one of the main factors causing high open-circuit voltage loss of devices.In this paper,an innovative research idea of introducing high power function p-type MoO₃ into the Mo back electrode and constructing a porous array structure is proposed in order to achieve efficient carrier separation and rapid transport along the pore wall at the interpenetrating CZTSSe/MoSe₂interface.Therefore,MoO₃ porous array structures were prepared directly on Mo electrode by constant-voltage electrochemical anodizing method.The influences of electrolyte,anodization voltage,anodization time,anodization temperature and other technological conditions on structural parameters such as pore size and film thickness were systematically optimized.The results show that MoO₃ prepared at 10 V anodization voltage has a larger pore diameter,which is more conducive to subsequent CZTS implantation along the pore wall.Based on the limited thickness of Mo electrode,MoO₃prepared at 7 min anodization time has the most ordered porous structure and appropriate film thickness.This work lays a necessary foundation for the preparation and performance improvement of efficient CZTSSe solar cells based on the back contact of CZTSSe/MoO₃interpenetrating array structure.2.Based on the prepared MoO₃ porous array structure,the structure parameters of porous MoO₃,that is,the effect of anodic oxidation process conditions on the photovoltaic performance of CZTSSe solar cells,were systematically studied.Firstly,MoO₃ prepared under constant voltage and different anodization time was used as the base,CZTS precursor film was spin coated with solution spin coating technology and selenation.Then,Cd S buffer layer and Zn O and ITO window layer were prepared on CZTSSe absorption layer by chemical bath deposition and magnetron sputtering,respectively.The device assembly was completed after evaporation of Al electrode.The results show that the porous microstructure of MoO₃ has a greater impact on the photovoltaic performance of CZTSSe devices.Compared with the cells prepared with simple Mo substrate(PCE=5.11%,V_OC=402 m V,J_SC=25.08 m A/cm²,FF=55.6%),the photovoltaic performance of CZTSSe devices is significantly improved.The devices assembled with MoO₃substrate anodization for 7 min showed significant improvement in performance,with the average efficiency increased to about 7.63%(V_OC=406 m V,J_SC=30.61 m A/cm²,FF=57.86%).3.On the basis of the above research work,the effect of anodization voltage（5-10V）on the performance of CZTSSe devices was systematically investigated by choosing the anodization time of 7 min.Under the same device assembly process conditions,the photovoltaic performance parameters of MoO₃ porous CZTSSe devices prepared based on 10 V anodization voltage have been improved,and the maximum photoelectric conversion efficiency has been increased to 9.00%(V_OC=422 m V,J_SC=33.63 m A/cm²).FF=63.35%).The test results show that MoO₃ obtained at 10 V anodization voltage has a relatively large aperture,and can form a good CZTSSe/MoO₃ array interpenetration structure and contact interface,which is conducive to the interface separation and transfer of carriers.The CZTSSe/MoO₃ back contact interface can effectively inhibit the recombination of separated carriers and prolong the carrier lifetime.The tail effect was reduced and the Urbach energy was reduced,and the overall performance of CZTSSe devices was improved.