Design multifunctional molecules of pentacene-functionalized covalent triazine frameworks as donors, acceptors, and transport materials in organic solar cells: A DFT study

The aim of this study is to design and analyze multifunctional organic molecules based on the organic molecule Covalent Triazine Framework (CTF0), functionalized by adding one to three organic pentacene units (CPNT1 to CPNT3), for application as donors and acceptors in the active layer of organic solar cells, as well as hole transport materials (HTMs) in both organic and perovskite solar cells. These compounds were investigated using DFT and TD-DFT methods with the LSDA functional and 6-31G(d,p) basis set in both the gas phase and chloroform solvent. The results showed a significant reduction in the energy gap from 2.86 eV in CTF0 to 0.95 eV in CPNT3. The HOMO and LUMO levels shifted from −6.66 and −3.80 eV to −5.05 and −4.10 eV, respectively. The absorption spectra exhibited a notable red shift from 400 nm to 637 nm, with CPNT2 showing the highest intensity (1.1673 a.u.). These molecules displayed strong spectral complementarity with well-known donor and acceptor materials such as PTB1–3, L14, N2200, and PC71BM. They can function as donors with N2200, L14, and PC71BM, and as acceptors with PTB1–3, with the combination PTB7-Th:CTF0 yielding the highest efficiency of 19.87%. Furthermore, energy alignment with perovskites such as MAPbI3, MAPbBr3, and FAPbI3, confirms their potential as efficient HTMs in perovskite solar cells. Features such as multiple charge transfer pathways, strong dipole moments, good solubility, significant structural stability, cost-effective synthesis, multifunctionality, organic nature, and environmental friendliness make these molecules highly promising candidates for next-generation organic and perovskite solar cells.