Passivating Contact Silicon Heterojunction Solar Cells Based On MoO_x Films Realized By Atomic Layer Deposition

The dopant-free carrier selective passivating contact material has been widely used in crystalline heterojunction silicon?c-Si?solar cells in recent years due to its wide band gap and simple preparation process.The energy conversion efficiency?PCE?of silicon solar cells based on MoO_X hole-selective passivating contact has reached 23.5%.Atomic layer deposition?ALD?technology has the advantages of high-quality conformality,uniform thickness,large area preparation and industrial compatibility,which indicates great application potential in the development of new passivating contact heterojunction c-Si solar cells.In this paper,the properties of MoO_X films prepared by ALD and its application in crystalline silicon solar cells are systematically studied.The main work includes:First,we optimized the growth temperature of ALD and prepared a crystalline silicon heterojunction solar cell based on c-Si?p?/MoO_X/Ag back contact under 140 ^oC through thickness optimization,which obtained 15.86%of PCE.X-ray photoelectron spectroscopy,transmission electron microscopy and other characterization methods were used to study the differences between MoO_X films prepared by thermal evaporation and ALD.Next,we tried to apply UV lighting into the ALD growth process to reduce O vacancies in the MoO_X film.The open-circuit voltage of the solar cell was improved obviously.In addition,the PCE of 16.34%was realized by improved ALD process,which is the highest value of c-Si?p?/MoO_X heterojunction cells currently prepared based on the ALD method.Next,we investigated the influence of the characteristics of the c-Si?p?/MoO_X and MoO_X/Ag interfaces on the performance of solar cells.The c-Si surface was treated with O₃ exposure,and good passivation performance was obtained on the c-Si?p?/MoO_Xinterface.The ultra-thin Cr O_X layer was sputtered on the MoO_X thin film to suppress Ag and O atoms in the MoO_X/Ag interface.Although the initial PCE decreased slightly to 14.82%,the stability of the solar cell was greatly improved,and its PCE did not decrease within 8 months.Finally,the band structures were simulated with AFORS-HET software,providing theoretical support for experimental data.In summary,this work systematically studies the process and properties of MoO_Xthin films grown by ALD,and proves its unique advantages and application potential in the preparation of MoO_X hole selective passivation contact,which provides support for the application of dopant-free passivated contact solar cells by ALD technology.