Preparation And Characterization Of Transparent Conductive Layer And Absorb Layer In Cu₂SnS₃ Film Solar Cells

With the increase of world’s energy crisis, the research of using solar energy is developing quickly. As an important device for using solar energy, solar cells are worth doing more research. Among all the main researched solar cells, copper zinc tin sulfide has attracted more interests due to its no-toxic and earth-abundant resource materials and high optical absorption coefficient. Photovoltaic cells using Cu2ZnSnS4 as the absorber material have achieved the highest record efficiencies up to 12.6%.However, due to the complex fabrication process, it is difficult to achieve the desired single phase Cu2ZnSnS4 without the binary or ternary impurity phases which inhibits the improvement of conversion efficiency. Recently,Cu2SnS3 has been investigated as the potential absorber materials for solar cell. Cu2SnS3 is a p-type semiconductor with a direct band gap of 0.92-1.6eV and a high absorption coefficient (≥104cm-1).In this paper, we research the transparent conductive layer and absorb layer in Cu2SnS3 film solar cells.Firstly,AZO/Mo/AZO and AZO/Mo/Cu/AZO structure transparent films have been designed and prepared by magnetron sputtering. The optical and electronic properties of the films have been investigated. The results show the AZO/Mo/AZO film with 9nm thickness Mo layer and 50nm thickness AZO layer has the best performance and perfect thermal stability. Moreover, the additional 3nm thickness Cu layer into AZO/Mo/AZO film may improve the optoelectronic performance of the film.Secondly, boron doped SnO2 films were prepared by ultrasonic spray pyrolysis. The structural and optoelectronic properties of boron doped SnO2 films have been investigated. The result confirms SnO2 film shows best optoelectronic performance when the B/Sn is 4at%.Finally, Cu2SnS3 film absorb layer were prepared by ultrasonic spray pyrolysis. The structural and optoelectronic properties of Cu2SnS3 films have been investigated. The result shows the higher Cu/Sn ratio and substrate temperature may change the dominant phase from tetragonal phase to monoclinic phase. The optical band gap of the films was reduced from 1.87eV to 1.03eV with the decrease of Cu/Sn precursor ratio. All thin films exhibit a minimum resistivity of 3.5×10-3Ωcm.