Synergizing MAPbI_3–<i>x</i>Cl_<i>x</i>-Based Solar Cells with Columnar Mesogenic Interfacial Layers for Superior Efficiency

Perovskite solar cells (PSCs) face several challenges, particularly the recombination of charge carriers at the interface between the perovskite material and the hole transport layer. This recombination is primarily attributed to poor charge transport and injection, which reduce the open-circuit voltage, efficiency, and stability of PSCs. In this study, we investigate the effect of incorporating a triphenylene-based columnar mesogen, 2,3,6,7,10,11-hexabutyloxytriphenylene (HAT4), as an interfacial layer between MAPbI3–xClx and PEDOT:PSS to improve the performance of PSCs. The quasi-one-dimensional (1D) charge propagation of the columnar interfacial layer significantly improves the short-circuit current and open-circuit voltage of PSCs with an ITO/PEDOT:PSS/HAT4/MAPbI3–xClx/PCBM/BCP/Ag configuration. This enhancement is attributed to the reduced recombination of the charge carriers at the interface. The best device achieved a maximum efficiency of 12.23% compared to 10.57% for the reference device without the columnar mesogen layer. Additionally, simulation results corroborate the experimental findings, revealing optimized intermolecular interactions and charge transfer between MAPbI3–xClx and the columnar mesogens. These results highlight the potential of incorporating an interfacial columnar layer to improve the performance of the PSC. This approach can be used in state-of-the-art solar cell technology to enhance efficiency and wider viability close to commercialization.