Optoelectronic Properties of Tetracyanoquinodimethane (TCNQ) Related Compounds for Applications to OSCs and OLEDs: A Theoretical Study

Tetracyanoquinodimethane (TCNQ) and related compounds are thoroughly investigated as potential innovative organic semiconductors and singlet fission (SF) materials. The TDDFT method with the PBE0/Def2-TZVP level is used to determine the geometrical structures, atomic dipole corrected Hirshfeld (ADCH) charge, population, dipole moment (μ), band gaps, different density of states (DOSs), excitation energies, hole-(λ_<i>H</i>) and electron-(λ_<i>E</i>) reorganization energies, SF properties, absorption-emission spectra, transition density matrix (TDM), electron localization function (ELF) of these molecules, and open circuit voltage (<i>V</i>_oc), fill factor (FF), and power conversion efficiency (PCE) of possible optoelectronic devices. At the CAM-B3LYP/6-311G** level, we examine the ground and excited state characteristics of 44 modeled TCNQ-related molecules. Two fundamental criteria, namely, the SF driving force (Δ = <i>E</i>(<i>S</i>₁) - <i>E</i>(<i>T</i>₁)) and the triplet-triplet annihilation (TTA) probability (Ω = <i>E</i>(<i>S</i>₁) - 2<i>E</i>(<i>T</i>₁)), have been analyzed to demonstrate the SF properties of these model materials. The current study reveals effective hole transport materials (HTMs) and electron transport materials (ETMs) in organic light-emitting diodes (OLEDs), and suitable SF materials in organic solar cells (OSCs) were chosen considering those multiple factors.