Computational and Stereochemical Design of Benzothiadiazole-Based Organic Sensitizers to Rival Metal-Complex Dyes in DSSCs

The development of organic sensitizers that provide efficient operation at low cost and maintain stability represents a vital requirement for advancing DSSC technology. The research combines analytical chemistry and DFT calculations to study three organic dyes containing benzothiadiazole (D2), quinoxaline (D4) and benzotriazole (D5) auxiliary acceptors for their structure-property relationships against established Ru-based complexes N3 and N719. The research evaluated ground state geometries and electronic structures and frontier molecular orbitals (FMOs) and absorption spectra and photovoltaic performance indicators including light-harvesting efficiency (LHE) and electron injection driving force (ΔGinject) and intramolecular charge transfer (ICT) characteristics. The selection of auxiliary acceptor components determines how organic dyes will behave optoelectronically according to our computational results. The benzothiadiazole-based dye (D2) demonstrates the longest wavelength absorption and strongest oscillator strength and best light absorption properties which match the performance of metal-based benchmarks. The electrostatic potential (ESP) and natural bond orbital (NBO) charge distribution analysis after excitation shows that all organic dyes achieve effective charge separation. The calculated LHE and ΔGinject values indicate that D2 represents the best organic sensitizer among the investigated compounds.