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Deformation-controlled solar thermal storage and release are important for thermal management of dynamic systems. However, few researchers have examined cyclic solid-state solar thermal utilization...

Four bisisoindigo (bis-IID) derivatives containing different numbers of electron withdrawing fluorine (F) or nitrogen (N) atoms and eight alternating copolymers of them with 2,2′-bithophene (BT) or 3,3′,4,4′-tetrafluoro-2,2′-bithiophene (4FBT) were synthesized. Depending on the numbers of F and N atoms incorporated, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of the polymers were feasibly tuned in the ranges of −5.51 to −6.06 eV and −3.64 to −4.01 eV, respectively. Top gate and bottom contact (TGBC) organic thin-film transistors (OTFTs) were fabricated to study the semiconducting properties of the polymers. Five polymers, i.e., P0F-BT, P2F-BT, P4F-BT, P2N2F-BT, and P0F-4FBT that contain 0–4 F and N atoms in the repeating unit, with HOMO and LUMO energy levels above −5.90 and −3.80 eV, respectively, all showed ambipolar OTFT characteristics. Three other polymers P2F-4FBT, P4F-4FBT, and P2N2F-4FBT that contain 6 or 8 F and N atoms with HOMO ...

Fluorinated conjugated polymers have been widely used in high performance polymer solar cells, but they showed limited application in field-effect transistors (FETs). In this paper, we focus on the influence of fluorine atoms upon charge transport of conjugated polymers in FET devices. Two series of conjugated polymers without or with fluorine atoms were designed and applied into FETs. Nonfluorinated conjugated polymers show high hole mobilties up to 11.16 cm2 V–1 s–1, while fluorinated polymers exhibit low hole mobilities below 1.80 cm2 V–1 s–1. Further investigation by differential scanning calorimetry (DSC) and 2D grazing-incidence wide-angle X-ray scattering (2D-GIWAXS) reveal that fluorinated conjugated polymers show low crystallinity and “face-on” orientation in thin films, explaining their poor hole mobilities in FET devices. Our results clearly show how the chemical structures influence the charge transport properties, which can be used to design new conjugated polymers toward high performance FETs.

The influence of the chemical structure of conjugated polymers on the nanophase separation and device performance in fullerene-based solar cells has been widely studied, while this is less investigated in non-fullerene solar cells. In this work, we design three conjugated polymers with different length of side chains, and we find that the length of side chains has little influence on the quantum efficiencies of non-fullerene solar cells. As a comparison, the length of side chains has a significant effect on the quantum efficiencies of fullerene-based solar cells. This indicates that morphology of the blended thin films in non-fullerene solar cells is rather independent of the length of the donor side chains, and the mechanism for morphology evolution in the non-fullerene system is completely different from that in the fullerene system. Our conclusion is confirmed by a variety of advanced characterization techniques. The studies reveal that in blended thin films based on the non-fullerene material the donor polymers with different side chains have a similar coherence length of π-π stacking, crystal size and domain purity, giving rise to similar internal quantum efficiency and power conversion efficiency of the solar cells.

Three donor–acceptor (D–A) alternating conjugated polymers with silafluorene as the donor unit, 5-alkyloxy-6-fluorobenzothiadiazole as the acceptor unit, and thiophene as the spacer has been synthesized and used as donor materials for polymer solar cells (PSCs). The introduction of a fluorine atom on the benzothiadiazole unit can lower the HOMO and LUMO energy level of the resulted polymers to afford higher open circuit voltage (Voc); whereas the introduction of a flexible alkyloxy chain on benzothiadiazole unit can increase the solubility of the resulted polymers without interfering the close packing of polymer chains in the solid state. High molecular weight polymers P-1a, P-1b, and P-1c, which are fully soluble in 1,2-dichorobenzene (DCB) at elevated temperature, have been prepared by Suzuki polycondensation. Among these polymers, P-1c exhibited the highest hole mobility up to 1.36 × 10–2 cm2 V–1 s–1. PSCs based P-1b:PC71BM demonstrated the highest Voc up to 0.98 V. P-1a:PC71BM based PSCs gave the high...

An amorphous copolymer (PBDT–BBT) of 4,8-bis(2-thienyl)benzo[1,2-b:4,5-b′]dithiophene and 5,5′-bibenzo[c][1,2,5]thiadiazole was synthesized by Stille coupling polymerization. PBDT–BBT exhibited good solution processability, excellent thermal stability with decomposition temperature of 437 °C, broad absorption (300–800 nm), deep HOMO level (−5.7 eV), and LUMO level (−3.7 eV). The microstructure order of PBDT–BBT thin films is not susceptible to thermal annealing temperature (80–200 °C). Field-effect transistors based on this polymer exhibited a charge-carrier mobility of 6 × 10–3 cm2 V–1 s–1, threshold voltage of −1 V, and on/off current ratio of 106 without any post-treatments. Thin film phototransistors of PBDT–BBT exhibited a photoresponsivity of 3200 mA W–1 and photocurrent/dark current ratio of 4 × 105.

A new conjugated copolymer PBDTTT-TIPS containing thiazolothiazole acceptor unit and triisopropylsilylethynyl (TIPS)-functionalized benzodithiophene donor unit was synthesized by Pd-catalyzed Stille coupling and compared with its alkoxy-substituted analogue PBDTTT-C12. PBDTTT-TIPS exhibits decomposition temperature of 377 °C, absorption maximum of 598 nm, HOMO level of −5.3 eV, and hole mobility as high as 1.2 × 10–3 cm2 V–1 s–1. Without any post-treatments, polymer solar cells based on the blend of PBDTTT-TIPS and PC71BM exhibited power conversion efficiency as high as 4.33%, which is 2 times that for device based on the PBDTTT-C12:PC71BM blend. TIPS and C12 side chains exhibit a little impact on absorption, HOMO level, and hole mobility of the polymers, but they significantly influence blend film morphology and photovoltaic performance. TIPS side chains induces excellent compatibility between PBDTTT-TIPS and PC71BM, and the PBDTTT-TIPS:PC71BM blend exhibits perfect phase separation scales around 10–20 n...

A novel donor-acceptor copolymer containing 9-alkylidene-9H-fluorene unit in the main chain, poly[9-(1-hexylheptylidene)-2,7-fluorene-alt-5, 5-(4,7-di-2-thienyl-5,6-dialkoxy-2,1,3-benzothiadiazole) ...

Four new copolymers P1–P4 containing the same backbone of bithiazole acceptor unit and benzodithiophene donor unit but different side chain pattern were synthesized by Pd-catalyzed Stille coupling....