Synthesis and Photovoltaic Properties of D–A Copolymers Based on Alkyl-Substituted Indacenodithiophene Donor Unit

Abstract

Four DÀA copolymers of tetradodecyl-substituted indacenodithiophene (IDT) donor unit with different acceptor units including bis(thiophen-2-yl)-bithiazole (BTz), bis(thiophen-2-yl)thiazolothiazole (TTz), bis(thiophen-2-yl)-tetrazine (TZ), and bis-(thiophen-2-yl)-benzothiadiazole (DTBT), PIDT-BTz, PIDT-TTz, PIDT-TZ, and PIDT-DTBT, were synthesized for the application as donor materials in polymer solar cells (PSCs). The copolymers possess good solubility benefitted from the four alkyl side chains on IDT unit, deeper HOMO levels at ca. À5.2 eV thanks to the IDT unit and tunable bandgap depending on the acceptor units. Among the copolymers, PIDT-TTz has the highest hole mobility (μ h ) of 4.99 Â 10 À3 cm 2 /V s. The power conversion efficiency (PCE) of the PSC based on PIDT-TTz/PC 70 BM (1:2 w/w) reached 5.79%, under the illumination of AM1.5G, 100 mW/ cm 2 . PIDT-DTBT film has the smallest bandgap of 1.68 eV and a higher μ h of 2.24 Â 10 À3 cm 2 /V s. The PSC based on PIDT-DTBT/PC 70 BM (1:3 w/w) exhibited an even higher PCE of 6.17% with a J sc of 13.27 mA/cm 2 , a V oc of 0.82 V, and a FF of 56.9%.

Recent Development on Narrow Bandgap Conjugated Polymers for Polymer Solar Cells

“…As expected, a higher hole mobility of 2.24 × 10 −3 cm 2 ·V −1 ·s −1 was obtained by the space charge limit current (SCLC) method using a device structure of ITO/PEDOT:PSS/polymer/Au. Eventually, the PCE of solar cell made up of P53:PC 71 BM blend showed a PCE of 6.17% with a J sc of 13.27 mA/cm 2 , a V oc of 0.82 V, and a FF of 56.9% (Table 4) [112].…”

Steric‐Hindrance Modulation toward High‐Performance 1,3‐Bis(thieno[3,4‐b]thiophen‐6‐yl)‐4H‐thieno[3,4‐c]pyrrole‐4,6(5H)‐dione‐Based Polymer Solar Cells with Enhanced Open‐Circuit Voltage

“…[25][26][27][28] Meanwhile, nitrogen atom is also utilized to tune the energy level toward high performance by substituting the carbon atom in fused rings to construct heterocyclic ring such as thiazole and [1,2,5]thiadiazolo [3,4-c]pyridine with unique characteristics. [29][30][31][32][33][34] As is well recognized, side alkyl chains are effective to enhance the solution processability of polymer donors and optimize blend morphology to achieve high device performance but can hardly modulate the electronic structure of conjugated backbones. Bao and co-workers [35] synthesized a homopolymer, poly(3,4-dihexyl-2,2′:5′,2′′-terthiophene), with proper degree of twist by introducing alkyl side chains with the specific number and at the specific position, which led to 19% enhancement in V oc as compared with that of poly(3-hexylthiophene) (P3HT)-based devices (0.735 vs 0.620 V), and similar J sc and fill factor (FF), and thus a slightly higher PCE of 4.2% without thermal annealing.…”

Synthesis and photovoltaic properties of new small molecules with rhodanine derivative as the end-capped blocks

“…Among various electron donor groups, 4,4,9,9-tetrakis(4-(dodecyloxy)phenyl)-4,9-dihydro-s-indaceno[1,2-b:5,6-b 0 ]-dithiophene (IDT) has drawn much attention because of their good photovoltaic performance [32]. The IDT can enhance inter-chain interaction of the molecules and lead to higher carrier mobility [32][33][34][35][36]. Herein, two acceptordonor-acceptor (A-D-A) type molecules DCAO3TIDT and DCNR3TIDT (Scheme 1) with IDT as the core D unit, CAO and CNR as the A unit, and trithiophene as the linker have been designed and synthesized.…”