Transport mechanisms limiting the efficiency of Sb₂(S_1-xSe_x)₃ solar cells

Antimony sulfide-selenide (Sb₂(S_1-xSe_x)₃) compounds have emerged as promising photovoltaic materials due to their abundance in nature, low toxicity, and long-term durability. With a tunable band-gap in the range of 1.1-1.7 eV, the compounds satisfy the requirement for single-junction cells and tandem solar cells. A power conversion efficiency of about 28% is theoretically possible for these absorber compounds, but the maximum value achieved in the laboratory currently hovers around 10%.

To address this Ayala-Mató et al. conducted a theoretical study on the effect of different transport mechanisms that may limit the performance of Sb₂(S_1-xSe_x)₃ solar cells, showing a correlation between the density of defects at the interfaces and the loss in photovoltaic efficiency.

To further understand the physical mechanisms behind the loss of efficiency, specifically the impact of bulk and interface defects on Sb₂(S_1-xSe_x)₃ solar cell behavior, the researchers modeled a FTO/CdS/Sb₂(S,Se)₃/Spiro-OMeTAD/Au solar cell configuration with SCAPS-1D software, and performed numerical simulations of different recombination mechanisms.

While previous work has focused on losses associated with bulk defects, the authors identified interface recombination as the main hurdle. To improve the efficiency, they suggest focusing on reducing the impact of CdS/Sb₂(SSe)₃ interface defects, which contributes to an open-circuit voltage deficit of almost 50%, as well as a 45% efficiency reduction compared to an ideal radiative regimen.

Consequently, the researchers recommend further studies on the use of alternative electron transport layers (ETL) to replace CdS in order to achieve better lattice coupling and band alignment.

Source: “Study of loss mechanisms on Sb₂(S_1-xSe_x)₃ solar cell with n-i-p structure: Towards an efficiency promotion,” by Fernando Ayala-Mató, Osvaldo Vigil-Galán, Miriam Marmara Nicolás-Marín, and Maykel Courel, Applied Physics Letters (2021). The article can be accessed at https://doi.org/10.1063/5.0032867 .