Thiophene/Phenylene/Thiophene-Based Low-Bandgap Conjugated Polymers for Efficient Near-Infrared Photovoltaic Applications

Abstract

We have prepared thiophene/phenylene/thiophene (TPT)-based low bandgap conjugated polymers exhibiting tunable energy levels and investigated their application in solar cells. By incorporating various electron-withdrawing comonomers through Stille coupling reactions, we obtained TPT-based donor/acceptor copolymers having bandgaps ranging from 1.0 to 1.8 eV. We compared the absorption spectra, electrochemistry, field effect hole mobility, and photovoltaic properties of these low bandgap TPT derivatives with those of poly(3-hexylthiophene) (P3HT). The absorption coefficients of the thin films fell in the range from 0.77 Â 10 5 to 1.4 Â 10 5 cm -1 . These materials displayed sufficiently high hole mobilities (>10 -3 cm 2 V -1 s -1 ) for efficient charge extraction and good fill-factors for organic photovoltaic applications. Electrochemical studies indicated desirable HOMO/LUMO levels, with a good correlation between the HOMO energy levels and the open circuit voltage (V oc ) when the polymers were blended with fullerene derivative as an electron acceptor. Power conversion efficiencies of up to 4.3% were achieved under AM 1.5G simulated solar light (100 mW cm -2 ). Our findings suggest that TPT derivatives presenting suitable electron-withdrawing groups are promising photovoltaic materials.

Thiadizoloquinoxaline-Based Low-Bandgap Conjugated Polymers as Ambipolar Semiconductors for Organic Field Effect Transistors

“…The design, synthesis, and characterization of TQ-containing polymers have undergone important progress in the last decade. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Most TQ-based polymers have been reported to show hole transport, while only few of them were presented as ambipolar semiconductors. 27,32,33 However, these systems usually exhibited very low mobilities (≤ 10 -2 cm 2 V -1 s -1 ) in OFETs.…”

“…In this study, PBDTTQ-3 shows significantly improved and balanced holes and electrons mobilities as high as 0. 22 39 were prepared according to the literature procedures.…”

Synthesis of novel thieno[3,2-b]thienobis(silolothiophene) based low bandgap polymers for organic photovoltaics

“…Indacenodithiophene (IDT), a ladder type donor moiety has been successfully introduced into 25 semiconducting polymers, which exhibited excellent hole mobilities in organic field effect transistors (OFET) and good photocurrent efficiencies in organic photovoltaic cells (OPV). [4][5][6][7] We have demonstrated that the judicious choice of bridging atom can not only have an influence on the crystallinity and solubility, 30 but also allows modulating the frontier energy levels. 8 The introduction of silicon as a bridging atom between adjacent aromatic units has several beneficial effects besides increasing the effective conjugation length and reducing the conformational disorder.…”

Conjugated Polymer Photovoltaic Materials

“…The coplanarity of the IDT unit could enhance interchain interaction of the polymers and is expected to afford higher hole mobility. Ting et al pioneered the IDT-based random and alternating copolymers for photovoltaic applications [107,108]. In 2008, two LBG IDT-based polymers with high hole mobility (3.4 × 10 −3 cm 2 V −1 s −1 ) were designed and synthesized for application in PSCs by Ting and coworkers [106].…”