New Bithiophene Extended IDIC-Based Non-Fullerene Acceptors and Organic Photovoltaics Thereof

Abstract

We developed new bithiophene extended electron acceptors based on m-alkoxythenyl-substituted IDIC with three different end groups, named as IDT-BT-IC, IDT-BT-IC4F, and IDT-BT-IC4Cl, respectively. The ultraviolet absorption maximum was redshifted and the bandgap was decreased as the strong electron accepting ability of the end group increased. A differential scanning calorimetry thermogram analysis revealed that all the new acceptors have a crystalline character. Using these acceptors and a bulk heterojunction structure using PBDB-T, inverted organic photovoltaic (OPV) devices were fabricated, and their performance was analyzed. Due to the red shift of the electron acceptors, the OPV active layer particularly, which was derived from IDT-BT-IC4F, exhibited increased absorption at long wavelengths over 800 nm. The OPV prepared using IDT-BT-IC exhibited a short-circuit current density (Jsc) of 2.30 mA/cm2, an open-circuit voltage (Voc) of 0.95 V, a fill factor (FF) of 45%, and a photocurrent efficiency (PCE) of 1.00%. Using IDT-BT-IC4F, the corresponding OPV device showed Jsc = 8.31 mA/cm2, Voc = 0.86 V, FF = 47%, and PCE = 3.37%. The IDT-BT-IC4Cl-derived OPV had Jsc = 3.00 mA/cm2, Voc = 0.89 V, FF = 29%, and PCE = 0.76%. When IDT-BT-IC4F was used as the electron acceptor, the highest Jsc and PCE values were achieved. The results show that the low average roughness (0.263 nm) of the active layer improves the extraction of electrons.

Exploration of nonlinear optical enhancement in acceptor–π–donor indacenodithiophene based derivatives via structural variations: a DFT approach

“…Current study focused on the computational investigation of NLO properties of a series of indacenodithiophene based chromophores (TNPR and TNPD1-TNPD6). For this study synthesized parent molecule (IDT-BT-IC) 30 with benzene ring of the acceptor group, respectively. In TNPD6, the utilized acceptor moiety is 2-(2-methylene-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (Scheme 1).…”

“…Current study focused on the computational investigation of NLO properties of a series of indacenodithiophene based chromophores ( TNPR and TNPD1–TNPD6 ). For this study synthesized parent molecule ( IDT-BT-IC ) 30 having A–D–A configuration was modified via structural tailoring to develop reference ( TNPR ) compound as shown in Fig. 1.…”

“…Table 2 shows that the HOMO/LUMO energies (−5.499/−3.303 eV) and band gap ( E gap = 2.196 eV) of the reference chromophore ( TNPR ) is in good agreement with the experimental values (−5.25/−3.82 eV and E gap = 1.43 eV). 39 In TNPD1–TNPD6 , a decrease in the E gap is observed, possibly attributed to the electron capturing nature of substituents (chloro, fluoro and cyano) located at acceptor group in comparison to the TNPR . However, TNPD5 demonstrates the smallest E gap value of 1.692 eV, owing to the presence of two cyano groups at the terminal acceptor.…”

“…Table 4 reveals that the computed λ max for TNPR is 706.785 nm, which shows excellent agreement with experimental absorption peak observed at 682 nm. 39 The λ max values for TNPD1–TNPD6 range from 694.745 to 852.242 nm, with corresponding transition energies in the range of 1.455 to 1.785 eV and oscillation strengths ranging from 0.553 to 0.997 in chloroform solvent. These transitions arise from the H → L interactions governed by the A–π–D configuration in the studied chromophores.…”