A strategy to enhance VOC of π-conjugated molecules based on thieno[2,3-b] indole for applications in bulk heterojunction organic solar cells using DFT, TD-DFT, and 3D-QSPR modeling studies

Abstract

Seven novel organic compounds BHJ-i (i = 1–7) based on carrying 8-alkyl-8H-thieno [2,3-b] indole as a donor, thiophene as a bridge and different acceptors were used for bulk heterojunction organic solar cells (BHJ). The main objective of this work was to find a better acceptor for π-conjugated molecules used in photovoltaic solar cells in order to improve their efficiency. The study was through DFT and TD-DFT quantum methods. Several optoelectronic properties of these materials, electronic properties (E_HOMO, E_LUMO, and E_gap), natural bond orbital (NBO) analysis, quantum chemical parameters (chemical hardness (η), chemical potential (μ) and electronegativity (χ)), UV-vis spectra and the open-circuit photovoltage (V_oc), were calculated. We also developed the 3D-QSPR model based on CoMFA and CoMSIA approaches to predict the most important three-dimensional properties of the structure of 8-butyl-8H-thieno [2,3-b] indol-2-yl) thiophen-2-yl) methylene derivatives, which allowed us to design new molecules and optimize their properties for a high-performance V_oc. The results indicated that the molecules in this work exhibit a theoretical power conversion efficiency of 7%. Finally, due to 3D-QSPR results, we have designed 10 new molecules, which have very interesting V_oc values.