Computational insight into the potential of tetraazapentacene as an active material in bulk-heterojunction solar cells

Abstract

Bulk heterojunction (BHJ) organic solar cells (OSCs) represent a class of thin-film photovoltaic devices that harness the unique properties of organic semiconductors. Despite remarkable progress, BHJ OSCs still face challenges related to stability, scalability, and long-term performance. This paper presents a thorough and comprehensive computational exploration of the potential viability of tetraazapentacene (TAP) as an active material in BHJ solar cells, utilizing a synergistic approach that combines density functional theory (DFT) and TD-DFT calculations. Our study is centered on investigating the impact of molecular modifications by exchanging CH with nitrogen in the pentacene framework on the overall performance as well as electrical and optoelectronic properties. This approach provides meaningful design recommendations for TAP's usage in OSC applications. The series of TAP structures (with and without inversion symmetry) were analyzed to see the effect of nitrogen incorporation on energy levels, bandgap, reorganization energy, electron and hole delocalization, charge transfer, and charge carrier mobility. Our findings, as revealed by the electron density distribution map, electron delocalization analysis e.g., electron localization function, local orbital locator, transition density matrix, and frontier molecular orbital analysis, suggest that the TAP may allow easier electron injection owing to its lower LUMO level and high EA value. TDM analysis reveals that TAPs lacking inversion symmetry exhibit higher electron–hole coherence across the structure, resulting in efficient electron transport. Applying the Scharber model formalism and utilizing TAPs as donors and PCBM as acceptors in BHJ solar cells, the power conversion efficiency was estimated to be approximately ~ 28%.

Graphical abstract

This study explores the potential of Tetraazapentacene (TAP) as an active material in bulk heterojunction (BHJ) organic solar cells through Density Functional Theory (DFT) and TD-DFT analyses. By substituting CH groups with nitrogen in the pentacene framework, the impact on optoelectronic and electrical properties is examined. TAP structures lacking inversion symmetry demonstrate enhanced electron delocalization, increased electron affinity, and stronger electron–hole coherence, which collectively improve electron transport. Utilizing the Scharber model, with TAP as the donor and PCBM as the acceptor, the estimated power conversion efficiency (PCE) reaches approximately 28%.