Optoelectronic and Photovoltaic Insights into C ₂ N/Dye Interfaces for Efficient Solar Energy Conversion: A Theoretical Study

Dye-sensitized solar cells (DSSCs) represent a promising technology for sustainable energy conversion; however, their performance optimization demands considerable experimental and computational effort. This study employs density functional theory (DFT) and time-dependent DFT (TD-DFT) to investigate the optoelectronic and photovoltaic properties of a C2N monolayer quantum dot and its complexes with two organic dyes including T2-1 and para-methyl red (PMR). Six dye/C2N configurations (T1–T3 and P1–P3) were computationally analyzed for their electronic structure, intramolecular charge transfer (ICT), and interaction with TiO2 electrodes. Key photovoltaic descriptors were evaluated to predict the device performance. Results revealed that the complexation of the dyes with C2N significantly enhances the light-harvesting efficiency, charge separation, and electron injection kinetics compared to those of isolated dyes on the TiO2 electrode. The calculated gas-phase values of short-circuit current densities and open-circuit voltages for T1, T3, P2, and P3 vary in the ranges of 51 to 53 mA cm–2 and 54 to 58 V, respectively, which shows their suitable photovoltaic performance for application in DSSCs. On the other hand, the T3 complex shows the highest open-circuit voltage (0.33 V) among the complexes while the highest short-circuit current densities (87.38 mA cm–2) is for the T1 complex in solvent (acetonitrile). The findings validate C2N as a viable photoanode material, and a cosensitizer demonstrated the efficacy of theoretical screening in improving DSSC performance.