Angular-Shaped 4,9-Dialkylnaphthodithiophene-Based Donor–Acceptor Copolymers for Efficient Polymer Solar Cells and High-Mobility Field-Effect Transistors

Abstract

Although the tetracyclic angular-shaped naphthodithiophenes (aNDTs) derivatives are an emergent building block for constructing promising semiconductor conjugated polymers, the absence of aliphatic side chains as solubilizing groups on the aNDTs greatly restricted their further application toward polymer synthesis. To create a new class of aNDT-based polymers for widespread applications in solution-processable OFETs and PSCs, side-chain engineering of the aNDT-based structures plays a pivotal role in improving solubility and optimizing electronic/steric properties associated with the resultant solar cell characteristics. In this research, we developed an efficient and straightforward methodology to construct the angular naphthodithophene core with regiospecific introduction of two aliphatic chains at its 4,9-positions via a base-induced double 6π-cyclization. For the first time, the corresponding 2,7-distannylated-4,9-dialkylated aNDT monomers were polymerized with FBT and DPP acceptors to make two new PaNDTDTFBT and PaNDTDPP donor−acceptor copolymers. The photovoltaic devices based on the PaNDTDTFBT:PC 71 BM blend not only showed a promising PCE of 6.52% with conventional configuration but also achieved a higher PCE of 6.86% with inverted configuration. Moreover, PaNDTDPP with strong intermolecular interaction achieved a high FET hole mobility of 0.202 cm 2 V −1 s −1 . ■ INTRODUCTIONDonor−acceptor (D−A) copolymers have been extensively utilized in organic photovoltaics (OPVs) and organic fieldeffect transistors (OFETs) due to their easy tunability of molecular properties and excellent solution processability. A variety of novel electron-rich conjugated building blocks have thus been developed for polymerization. 1 Compared to the tricyclic benzodithiophene derivatives representing the most successful component for constructing high-performance D−A copolymers of OPVs, 2 the tetracyclic naphthodithiophenes (NDTs) also attract growing attention considering their extended conjugation as well as diverse structures. 3 Depending on the molecular geometry, the NDT derivatives can have linear-shaped (lNDT) and angular-shaped (aNDT) isomeric structures (Figure 1). It was found that aNDT-based copolymers have higher ordered structures than the lNDTbased copolymers, thereby achieving higher OFET mobilities. 4 Furthermore, the aNDT molecules exhibit lower-lying HOMO energy levels than the lNDT counterparts, 5 which are beneficial for better air stability and greater open-circuit voltage (V oc ) for OPVs. To fully exploit the aNDT-containing polymers for the optoelectronic applications, side-chain engineering by introducing solubilizing groups onto an aNDT framework is highly essential to not only ensure the solution processability but also induce suitable molecular packing. 6 To address the issue, Takimiya and Osaka first introduced two alkyl groups at the outer positions (5,10-positions) of the central naphthalene moiety in the aNDT. 7 Compared to the polymer incorporating the unsubstituted aNDT units, 8 the 5,10-dialkyl aN...

Synthesis of a 4,9-Didodecyl Angular-Shaped Naphthodiselenophene Building Block To Achieve High-Mobility Transistors

“…In the presence of 1,8-diazabicyclo[5.4.0]­undec-7-ene (DBU) with microwave irradiation, compound 6 underwent an intramolecular benzannulation to form compound 7. The mechanism involves propargyl-allenyl isomerization followed by 6π-electrocyclization/aromatization. , PtCl 2 -catalyzed benzannulation of 7 via a 6-endo-dig fashion afforded 4,9-α-aNDS with two dodecyl groups regiospecifically at the 4,9-postions. 4,9-α-aNDS was further stannylated to yield the target Sn-4,9-α-aNDS monomer in a high yield of 95%.…”

“…Ladder-type conjugated structures with rigid and coplanar molecular frameworks feature longer effective conjugation, narrow optical bandgap, and strong intermolecular π–π interactions which are ideal characteristics for organic field-effect transistors (OFETs). − Acenedithiophenes, made up of linearly fused benzene rings with two terminal thiophenes, are particularly superior building blocks due to their coplanar structures, facile functionalization, and high charge mobility. Benzodithiophene (BDT)-incorporating donor–acceptor (D-A) copolymers have achieved high-efficiency solar cells, − whereas anthradithiophene (ADT) derivatives have shown high mobilities in p -type OFETs − More recently, growing research effort is directed toward the synthesis and molecular properties of naphthodithiophenes (NDT) having versatile isomeric structures. − In addition to the linear-shaped NDTs, angular-shaped NDTs (aNDT) can have two α-aNDT and β-aNDT isomers (see Chart ). Takimiya and Osaka et al first incorporated alkyl chains into an α-aNDT to ensure the solubility of the resulting polymers for solution-processable transistors and solar cells. , We recently described a synthetic strategy to introduce two alkyl groups at 4,9- or 5,10-positions of both α-aNDT and β-aNDT .…”

Highly Luminous Sky-Blue Organic Light-Emitting Diodes Based on the Bis[(1,2)(5,6)]indoloanthracene Emissive Layer

“…61,62 In the realm of organic electronics, base catalysed isomerisation of alkynylated oligomers to polyaromatic semiconductors has been used for the synthesis of coronenes 63,64,65,66 and thienoacenes of various number of rings and sulfur atoms. 67,68,69,70 Here, we demonstrate that this strategy is also suitable for the synthesis of bis-[(1,2)(5,6)]indoloanthracene (4) a new π-extended nitrogen based heterocycle.…”

Nanographene and Graphene Nanoribbon Synthesis via Alkyne Benzannulations

“…Müllen and coworkers reported the synthesis of CDIs using a DBU-promoted alkyne benzannulation reaction of diethynyl-substituted PDIs 120 to arrive at alkylated CDI derivatives 121 in good yields (Scheme 23) [123]. Since this report, there have been many examples of base-induced alkyne benzannulations to produce various NGs [122,124,125], heteroatom-containing NGs [126], and polymers [127,128,129].…”