The Effect Of Interface Opimization On The Device Performance Of Antimony Selenide Solar Cells

Antimony selenide（Sb₂Se₃）material has attracted more and more attention due to its high absorption coefficient,suitable optical bandgap,low-cost,low toxicity and stability.At present,the highest efficiency of Sb₂Se₃ solar cells is 9.2%,which is far lower than the theoretical efficiency of 30%.The losses of cell efficiency are mainly attributed to high open-circuit voltage loss and high interface recombination.In this paper,the following two aspects were studied:（1）p-type Cu₂Zn Sn S₄ nanoparticles（CZTS NPs）as a hole transport layer was used to construct a n-i-p typed Sb₂Se₃ solar cells for reducing carrier combination at the back interface.;（2）Al₂O₃ interface layer was used as an interface layer between CdS and Sb₂Se₃ to increase open-circuit voltage and decrease interfacial recombination.The details are as follows:（1）CZTS NPs was used as a hole transport layer to construct a n-i-p typed Sb₂Se₃solar cells.It is found that the introduction of CZTS NPs hole transport layer can effectively cover the raised petale-like Sb₂Se₃ grains,thus can reduce the surface roughness of Sb₂Se₃ and improve back interface performance.Consequently,the dark saturation current（j₀）decreased from 3.35×10^-4 m A/cm~2 to 1.20×10^-4 m A/cm~2,indicating reduced carrier recombination at the back interface..The device performance results show that the introduction of CZTS will facilitate to improve the long wave response and the fill factor of the device,but slightly reduce the open circuit voltage.The slightly decrease of open-circuit voltage is due to the Fermi level of CZTS NPs is higher than the Fermi level of Sb₂Se₃ material according to Ultraviolet photoelectron spectroscopy（UPS）analysis of CZTS NPs,which will cause reduced built-in potential in Sb₂Se₃ solar cells.Finally,a champion efficiency of 6.06%(V_oc=0.409 V,J_sc=27.12 m A/cm~2,FF=54.6%)has been achieved at a n-i-p Sb₂Se₃ solar cells with FTO/CdS/Sb₂Se₃/CZTS/C device configuration,a 15.4%higher than the device efficiency of 4.94%(V_oc=0.420 V,J_sc=24.11 m A/cm~2,FF=51.8%)without a CZTS hole transport layer.（2）Al₂O₃ layer prepared by magnetron sputtering was used as an interface layer between CdS and Sb₂Se₃ With the increase of thickness of Al₂O₃ interface layer from 0 to22 nm,the ratios of texture coefficient TC_（221）/TC_（120）of Sb₂Se₃ film increase from 7.31to 43.6,indicating that Al₂O₃ interface layer can effectively enhance[221]-oriented growth and inhibit[120]-oriented growth.of Sb₂Se₃ film.Meanwhile,the surface roughness of Sb₂Se₃ film decreases from 40.6 nm to 28.3 nm.When the thickness of Al₂O₃ interface layer is as thin as 6.6 nm,the j₀ of the Sb₂Se₃ solar cell decreases from 1.44×10^-4 m A/cm~2to 7.9×10^-5 m A/cm~2 compared with Sb₂Se₃ solar cell without an Al₂O₃ interface layer,and the V_oc,J_sc and FF of the device are all improved.In particular,the open circuit voltage of the device was increased by 10%from 0.420 V to 0.462 V.Finally,Sb₂Se₃ solar cell with Al₂O₃ as an interface layer has realized a 6.25%champion efficiency(V_oc=0.462 V,J_sc=26.46 m A/cm~2,FF=51.1%),and the device performance is improved by 20.9%compared with the device without an Al₂O₃ layer.