Benzothiadiazole[1,2-b:4,3-b′]dithiophene, a new ladder-type multifused block: Synthesis and photovoltaic application

Abstract

a b s t r a c tA new fused building block benzothiadiazole [1,2-b:4,3-b 0 ] dithiophene (BTDT) was prepared by covalently locking thiophene unit on both sides of benzothiadiazole (BT). On the basis of this building block, a series of conjugated copolymers containing homopolymer (P1) or electron-rich comonomers such as carbazole (P2), benzodithiophene (P3 and P4) and thiophene (P5) were obtained. All polymers have good solubility in common organic solvents. The thermal, optical, electrochemical and photovoltaic properties of the polymers were investigated systematically. The thiophene units, which were covalently fastened to the BT moiety, enlarged the planarization of the polymer backbone and thus induced stronger intermolecular p-p interaction, meanwhile, decreased the electron-withdrawing ability of the BT unit. The device based on P3:PC 71 BM exhibited a high open-circuit voltage (V OC ) of 0.96 V and moderate power conversion efficiency (PCE) of 2.16%.

Polymer design for solar cell – Current trend and future scenario

“…The thiophene units, which were covalently fas- tened to the BT moiety, enlarged the planarization of polymer backbone and thus, induced stronger intermolecular p-p interaction and meanwhile, this decreased the electron-withdrawing ability of the BT unit. Due to this, the PSC of copolymer P80 and PC 71 BM exhibited a moderate PCE of 2.16% [78] (see Fig. 8).…”

One-pot homopolymerization of thiophene-fused isoindigo for ambient-stable ambipolar organic field-effect transistors

“…35 Yang et al mentioned the homopolymerization of a dibrominated monomer with benzothiadiazole[1,2-b:4,3-b 0 ]dithiophene core in the presence of hexamethylditin. 36 More recently, such a one-pot Stille homopolymerization was applied in the synthesis of an insulated conjugated polymer. 42 However, compared to the vast number of the reported cases on the copolymerization between a dibrominated monomer with a diboronated or distannylated monomer, the examples for the one-pot Suzuki or Stille homopolymerization are quite limited.…”

“…Here we report the synthesis of PTII, which was directly obtained by a one-pot polymerization method using a,a 0 -dibrominated TII (2Br-TII) as the starting material, either via Suzuki condensation polymerization in the presence of one equivalent of bis(pinacolato)diborane (for PTII-1) or Stille condensation polymerization in the presence of one equivalent of hexamethyldistannane (for PTII-2), respectively. It is worthwhile to mention that such one-pot Suzuki and Stille homopolymerization methodologies are much less studied, [34][35][36] but it provides an easier way to construct conjugated homopolymers, since the tedious and moisture-sensitive preparation and purication of the borylated or stannylated comonomers are avoided. To further elucidate the structure-property relationship of PTII, TII was also copolymerized with II to give P(TII-co-II) as a comparison.…”

Recent Development on Narrow Bandgap Conjugated Polymers for Polymer Solar Cells

“…In 2007, Heeger’s group reported the polymer PCPDTBT ( Figure 2 ), which was a kind of donor-acceptor conjugated polymer with a lower band-gap (1.46 eV). The PCE can reach 5.5% in the optimized device [ 26 ]. Although the improved J sc was achieved, the V oc was still much low.…”