Enhanced photovoltaic performance in Sb2(S,Se)3/CuI planar-heterojunction solar cells: Insights from device simulation

In state-of-the-art ${\mathrm{Sb}}_2{(S,Se)}_3$ solar cells, the absorber is sandwiched between toxic-$\mathrm{CdS}$ and expensive $\mathrm{Spiro}-OMeTAD$, serving as electron and hole transport layers ($\mathrm{ETL}\mathrm{and}\mathrm{HTL}$), respectively. Adhering to the current trend in green chemistry, it is crucial to either reduce the usage of aforementioned materials or find their alternatives. In this context, this work investigates the feasibility of employing $\mathrm{Sn}{O}_2/CdS$ bilayer $\left(ETL\right)$ and $\mathrm{CuI}$ ($\mathrm{HTL})$ in ${\mathrm{Sb}}_2{(S,Se)}_3$ solar cells. The simulation results reveal that substituting $\mathrm{CdS}$ with $\mathrm{Sn}{O}_2/CdS$ bilayer can potentially improve photocurrent by 2 $\mathrm{mA}{\mathrm{cm}}^{-2}$, while $\mathrm{Spiro}-OMeTAD$ with $\mathrm{CuI}$ can boost photovoltage by $100mV$. Consequently, a $\mathrm{PCE}$ of $21.19\%$ and 17.82 % was demonstrated in optimized devices, based on $\mathrm{Au}$ and Carbon electrode, respectively. This work endorses $\mathrm{CuI}$ as an efficient heterojunction partner with ${\mathrm{Sb}}_2{(S,Se)}_3$ absorber layer and provides critical insights for the fabrication of highly efficient $(PCE>20\%)$ and cost-effective ${\mathrm{Sb}}_2{(S,Se)}_3$ solar cells.