Synthesis of New Thiadiazole-Containing Polythiophene Derivatives and Their Application to Organic Solar Cells

Abstract

New thiadiazole-containing -conjugated polymers have been successfully synthesized by the Stille coupling reaction of 2,5-bis(5'-bromo-3',4'-dihexylthien-2'-yl)-1,3,4-thiadiazole (1) with various distannyl compounds as acceptor and donor monomer units, respectively. Most of polymers showed lower highest occupied molecular orbital (HOMO) energy level than poly(3-hexylthiophene) (P3HT). It was found that the bulky side chains of donor units tend to prevent the arrangements of main chains. The polymer comprised of thienothiophene donor units without side chains displayed relatively high solar cell performance with a power conversion efficiency (PCE) of 2.8% under the illumination of AM 1.5, 100 mW/cm 2 .

Synthesis of D‐A copolymers based on thiadiazole and thiazolothiazole acceptor units and their applications in ternary polymer solar cells

“…The deeper HOMO energy level of these copolymers is beneficial to achieve the high value of V OC in the PSCs. Moreover, the HOMO energy level of the P123 is upshifted compared to the polymer PB2F, 38 as reported by Zhang et al, which may be due to the weak BDTTz donor unit in P123 .…”

“…Many D‐A copolymers using benzotriazole, benzothiadiazole, and quinoxaline as acceptors, have been designed and used as a donor for fullerene‐free PSCs 35–37 . Additionally, due to the absence of hydrogen atoms at 3‐ and 4‐positions, the size of TDz is a smaller as compared to thiophene 38–40 . This compact structure of TDz compared to benzothiadiazole also provides a significant advantage in suppressing the torsion of the polymer backbone and also reduces the steric hindrance.…”

Realizing Over 13% Efficiency in Green‐Solvent‐Processed Nonfullerene Organic Solar Cells Enabled by 1,3,4‐Thiadiazole‐Based Wide‐Bandgap Copolymers

“…TDZ cycle is highly polarizable with a large electron affinity, which can be used as an excellent electron acceptor block for constructing high‐performance D–A copolymers in the OSCs. However, TDZ‐based copolymer donors received less attention and showed unsatisfactory device performances . On the other hand, BDT unit features a weak electron‐donating property, which is a good candidate as the donor block for building wide‐bandgap copolymers.…”