Chitosan-supported graphite as an anodic counter electrode for stable organic solar cell applications: insight from...

The course for improving the stability and electronic transport properties of electrode materials is crucial for obtaining high-performance organic solar cells and warrants attention. The current study explores the potential of graphite as an anode-based counter electrode material for organic solar cell applications using a first-principles calculations approach. The study focuses on the effect of chitosan molecules on the charge transfers and optical response properties of graphite. The adsorption of chitosan onto graphite showed a negligible lattice mismatch and decreased cohesive energies, suggesting improved stability. The increased density of states of graphite with chitosan incorporation suggests the presence of delocalized electronic states near the Fermi level. The optical response properties show increased absorption with chitosan adsorption on graphite surface, suggesting the introduction of surface dipoles and light absorption. The variation of the refractive index of graphite ( $1.23\to 1.45$ ) with chitosan adsorption suggests significant interfacial charge transfers. The bulk of the charge transfer behaviour can be attributed to the π-π and n-π transitions. Hence, chitosan-supported graphite heterostructures can act as potential anode electrode materials for organic solar cells and other optoelectronic applications. METHODS: All computations were performed using density functional theory (DFT) as implemented in the CASTEP code, the DMol package, and the adsorption locator tool. The geometric structures were optimized using the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional. The electronic and optical properties were studied using the same norm-conserving pseudopotentials of the CASTEP code.