Synthesis of a New Ladder-Type Benzodi(cyclopentadithiophene) Arene with Forced Planarization Leading to an Enhanced Efficiency of Organic Photovoltaics

Abstract

We have developed a new heptacyclic benzodi-(cyclopentadithiophene) (BDCPDT) unit, where 3,7-positions of the central benzo [1,2-b:4,5-b′]dithiophenes (BDT) subunit are covalently rigidified with 3-positons of the two external thiophenes by two carbon bridges, forming two external CPDT rings that share two thiophene rings with the central BDT core. The distannyl-BDCPDT building block was copolymerized with 1,3-dibromo-thieno[3,4-c]pyrrole-4,6-dione (TPD) by Stille polymerization to afford a new alternating donor−acceptor copolymer PBDCPDT-TPD. The implementation of forced planarization greatly suppresses the interannular twisting to extend the effective conjugated length and preserve the interactions between the donor and acceptor segments. The device using the PBDCPDT-TPD/PC 71 BM (1:3 in wt%) blend processed with dimethyl sulfoxide as an additive delivered a marked PCE of 6.6% which represents a significant enhancement compared to the device using the corresponding nonfused polymer analogue with a PCE of 0.2%.

Unconjugated Side‐Chain Engineering Enables Small Molecular Acceptors for Highly Efficient Non‐Fullerene Organic Solar Cells: Insights into the Fine‐Tuning of Acceptor Properties and Micromorphology

“…To make further breakthroughs, creating new cores (the D moiety) has been identified as an effective and sustainable approach as it is the most direct way to modulate the property considering the relatively limited choices of end groups. Among the emerging core units, benzo[1,2‐ b :4,5‐ b ′]di(cyclopenta[2,1‐ b :3,4‐ b ′]dithiophene (BDCD) is one of the isomers of IDTT with marshaling sequence of thiophene, and the NFBDT, the SMA based on the BDCD core, possesses more modification sites and shows a redshifted absorption profile relative to ITIC.…”

Synthesis of a Novel Low‐Bandgap Polymer Based on a Ladder‐Type Heptacyclic Arene Consisting of Outer Thieno[3,2‐b]thiophene Units for Efficient Photovoltaic Application

“…Recently, several highly coplanar donor units with extended π‐conjugation by fastening or fusing adjacent rings have been reported. The central cores can be benzene, thiophene, and other fused three rings like fluorene, carbazole, silole, and benzodithiophene 19–26. The outer thiophene or benzene rings are covalently fastened or fused to the central cores, affording largely coplanar and symmetric structures.…”

Synthesis and Photovoltaic Properties of New Multifused Anthradithiophene‐Based Narrow‐Bandgap D–A Copolymers

“…Notably, the PCE of all inverted solar cell devices are over two times higher than their corresponding conventional devices. The improved efficiencies for the inverted devices are mainly due to the close energy alignment between the work function of MoO 3 and the HOMO energy levels of copolymers, facilitating better charge transporting and increased J sc (4.87 vs 2.30 mA cm −2 for the PADTDPP system, 5.89 vs 3.00 mA cm −2 for the PADTTPD system, and 5.00 vs 3.97 mA cm −2 for the PADTFBO system).…”