Simulation analysis of Cd_1-xZn_xS/Sb₂(Se_1-xS_x)₃ solar cells with n-i-p structure

In this work, the use of Cd_1-xZn_xS ternary compound as an alternative ETL layer to CdS in solar cells with FTO/CdS/Sb₂(Se_1-xS_x)₃/spiro-OMeTAD/Au structure is evaluated for the first time. Numerical calculations on Sb₂(Se_1-xS_x)₃ solar cells with CdS and Cd_1-xZn_xS as ETL layers are performed for comparison. Experimental data reported for CdS/Sb₂(Se_1-xS_x)₃ solar cell are reproduced with good agreement, thereby validating our model. A solar cell efficiency enhancement from 10.0% to 13.3% is found with the use of a Cd_1-xZn_xS layer with a Zn concentration of 0.4 and a thickness of 70 nm. The impact of defects at Cd_1-xZn_xS/Sb₂(Se_1-xS_x)₃ and Sb₂(Se_1-xS_x)₃/spiro-OMeTAD interfaces and Sb₂(Se_1-xS_x)₃ bulk on solar cell behavior is evaluated. In particular, we found that defects at Cd_1-xZn_xS/Sb₂(Se_1-xS_x)₃ interface stand as the main limiting factor of this technology. Finally, an efficiency of 14.8% is demonstrated with the reduction of interface defects to values of about 10¹¹ cm⁻². Under this condition, more attention should be paid to reducing the effect of series and shunt resistances in order to increase solar cell efficiency from 14.8% to 17.4%.