Optimization Of Light Absorbing Layer Of Antimony Selenide Thin Film Solar Cells

Antimony selenide(Sb₂Se₃)has the characteristics of appropriate band gap,high light absorption coefficient and excellent grain boundary,which fully shows its development potential as a thin-film solar cell.At the same time,it has the advantages of rich raw materials,simple preparation methods and stable performance.It has developed rapidly in recent years,and has reached a conversion efficiency of 9.2%.However,according to the Shockley–queisser limit,the photoelectric conversion efficiency of Sb₂Se₃ solar cell device needs to be further improved.Because(Sb₄Se₆)_n nanoribbons have a one-dimensional chain structure with strong anisotropy,and the carrier transport rate along the nanoribbons is much higher than that across the nanoribbons,it is very important to form an efficient carrier transport channel by controlling the growth orientation of Sb₂Se₃ grains.Based on this,in this paper,Sn O₂ thin film doped with Cd Cl₂ is used as the electron transport layer of Sb₂Se₃ solar cell.The regulation of preferred orientation during grain growth and the evolution of microstructure were studied.Firstly,Sb₂Se₃ thin films with different preferred orientations were prepared by close space sublimation by controlling the substrate temperature of the evaporation device,and the performance of the corresponding Sb₂Se₃ solar cells was compared and analyzed.The results show that Sb₂Se₃ grains are difficult to crystallize at too low substrate temperature,while Sb₂Se₃grains are difficult to adsorb on substrate surface at too high substrate temperature.It is found that the Sb₂Se₃ thin film grown at 250°C is the best in the longitudinal direction,and the photoelectric conversion efficiency of the device is 3.80%.Then,through the numerical modeling and analysis of wx-AMPS,it is concluded that the(101)orientation preference due to the increase of substrate temperature is not conducive to the transport of carriers in the light absorbing layer,and improves the defects at the back end of the light absorbing layer,which increases the carrier recombination rate and leads to the decline of device performance.Secondly,the growth stages of Sb₂Se₃ films with substrate temperature of 250°C were studied by controlling the evaporation time.The results show that too low thickness of light absorbing layer makes it difficult to fully absorb photon energy,and too high thickness of light absorbing layer will increase the defects of battery devices.In this paper,through the study of the crystallization process of Sb₂Se₃ film,the thickness of the light absorbing layer is optimized,and finally evaporated at the evaporation source temperature of 520°C for 60 s to obtain the Sb₂Se₃film with clear grain boundary and low film roughness.Finally,the best conversion efficiency of5.07%is obtained.Then,through the numerical modeling and analysis of wx-AMPS,it is found that the appropriate thickness of the light absorbing layer can not only improve the utilization of photons,but also alleviate the carrier recombination caused by the back-end defects of the light absorbing layer.Finally,Sb₂Se₃ solar cells with continuously adjustable band gap can be realized by interdoping because Sb₂Se₃ and Sb₂S₃ have similar structures.In this paper,wx-AMPS software was used to simulate and optimize solar cells with different band gap structures Sb₂(S,Se)₃.It was found that the band gap gradient formed by solar cells with decreasing band gap structure was beneficial to hole transport,and their special band gap structure could form additional electric fields that assisted hole transport but hindered free electron transport.Finally,the theoretical photoelectric conversion efficiency of 14.42%is obtained.Then,by analyzing the thickness and defect state,the application range is obtained:when the defect state density is 10¹⁶cm^-3 and the thickness is 1.25-1.75?m,the Sb₂(S,Se)₃ solar cell with decreasing band gap structure can play the best performance advantage.