Acceptor–Donor–Acceptor Small Molecules Based on Indacenodithiophene for Efficient Organic Solar Cells

Abstract

Four A-D-A type small molecules using 4,4,9,9-tetrakis(4-hexylphenyl)- indaceno[1,2-b:5,6-b']dithiophene as central building block, bithiophene or terthiophene as π-bridges, alkyl cyanoacetate or rhodanine as end acceptor groups were synthesized and investigated as electron donors in solution-processed organic solar cells (OSCs). These molecules showed excellent thermal stability with decomposition temperatures over 360 °C, relatively low HOMO levels of -5.18 to -5.22 eV, and strong optical absorption from 350 to 670 nm with high molar extinction coefficient of 1.1 × 10(5) to 1.6 × 10(5) M(-1) cm(-1) in chloroform solution. OSCs based on blends of these molecules and PC71BM achieved average power conversion efficiencies of 2.32 to 5.09% (the best 5.32%) after thermal annealing. The effects of thiophene bridge length and end acceptor groups on absorption, energy level, charge transport, morphology, and photovoltaic properties of the molecules were investigated.

π-Linkage effect of push-pull-structure organic small molecules for photovoltaic application

“…In 2014, Bai et al [35] reported four A-D-A typed OSMs, namely 13a-d, which bearing 4,4,9,9-tetrakis (4-hexylphenyl)-indaceno [1,2-b:5,6-b′] dithiophene as the central donor segments, alkyl cyanoacetate or rhodanine as the terminal acceptor groups and bithiophene or terthiophene as the π-conjugation bridges. The charge mobility data of 13/PC 71 BM blend films are shown in Table 2.…”

A planar electron acceptor for efficient polymer solar cells

“…The rigid and coplanar structure of IDT can prevent the molecular skeleton from torsional or conformational change, and enhance charge carrier mobility. 45,46 Finally, the tetrahexylphenyl groups as peripheral substituents of the coplanar backbone ensure solution process ability, reduce intermolecular interactions, and prevent the acceptor from strong self-aggregation and large phase separation in blended films.…”

Small Molecules Based on Thieno[3,4-c]pyrrole-4,6-dione for High Open-Circuit Voltage (VOC) Organic Photovoltaics: Effect of Different Positions of Alkyl Substitution on Molecular Packing and Photovoltaic Performance

“…As expected, two SMs exhibited low-lying HOMO (−5. [3,4-c]-pyrrole-4,6(5H)-dione) (6,7). After compound 4 (or 5) (0.53 mmol) was dissolved in CF (20 mL), bromine (1.17 mmol) was added dropwise into the solution.…”