High Open-Circuit Voltage Solar Cells Based on New Thieno[3,4-c]pyrrole-4,6-dione and 2,7-Carbazole Copolymers

Thieno[3,4-c]pyrrole-4,6-dione-based conjugated polymers for organic solar cells

Thieno[3,4-c]pyrrole-4,6-dione (TPD) based conjugated polymers as an electron donor, acceptor and single-component for application in organic solar cells in the past ten years have been intensively reviewed in this Feature Article.

Anthanthrene-based conjugated polymers for the dispersion of single-walled carbon nanotubes

Four new copolymers based on anthanthrene for the dispersion of semiconducting SWNTs of various diameters have been synthesized.

Small Molecules Derived from Thieno[3,4-c]pyrrole-4,6-dione (TPD) and Their Use in Solution Processed Organic Solar Cells

In this work, microwave synthesis, chemical, optical and electrochemical characterization of three small organic molecules, TPA-TPD, TPA-PT-TPD and TPA-TT-TPD with donor-acceptor structure and their use in organic photovoltaic cells are reported. For the synthesis, 5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione was used as electron withdrawing fragment while the triphenylamine was used as electron donating fragment. Molecular electronic geometry and electronic distribution density were established by density functional theory (DFT) calculations and confirmed by optical and chemical characterization. These molecules were employed as electron-donors in the active layer for manufacturing bulk heterojunction organic solar cells, where [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) was used as electron-acceptor. As cathode, Field's metal (FM), an eutectic alloy (Bi/In/Sn: 32.5%, 51%, and 16.5%, respectively) with a melting point above 62 °C, was easily deposited by drop casting under vacuum-free process and at air atmosphere. Prepared devices based on TPA-TPD:PC71BM (1:4 w/w ratio) presented a large VOC = 0.97 V, with JSC = 7.9 mA/cm², a FF = 0.34, then, a power conversion efficiency (PCE) of 2.6%.

Recent Advances in Wide-Bandgap Photovoltaic Polymers

The past decade has witnessed significant advances in the field of organic solar cells (OSCs). Ongoing improvements in the power conversion efficiency of OSCs have been achieved, which were mainly attributed to the design and synthesis of novel conjugated polymers with different architectures and functional moieties. Among various conjugated polymers, the development of wide-bandgap (WBG) polymers has received less attention than that of low-bandgap and medium-bandgap polymers. Here, we briefly summarize recent advances in WBG polymers and their applications in organic photovoltaic (PV) devices, such as tandem, ternary, and non-fullerene solar cells. Addtionally, we also dissuss the application of high open-circuit voltage tandem solar cells in PV-driven electrochemical water dissociation. We mainly focus on the molecular design strategies, the structure-property correlations, and the photovoltaic performance of these WBG polymers. Finally, we extract empirical regularities and provide invigorating perspectives on the future development of WBG photovoltaic materials.

Carbazole-based copolymers via direct arylation polymerization (DArP) for Suzuki-convergent polymer solar cell performance

Direct arylation polymerization (DArP) is used to synthesize a variety of carbazole-based copolymers for evaluation in solar cells.

Incorporating a vertical BDT unit in conjugated polymers for drastically improving the open-circuit voltage of polymer solar cells

High open circuit voltages (V_ocs) of over 1.0 V were obtained for solar cell devices based on vertical BDT-containing conjugated polymers.

Linked-Acceptor Type Conjugated Polymer for High Performance Organic Photovoltaics with an Open-Circuit Voltage Exceeding 1 V

A linked-acceptor type conjugated polymer is designed and sythesized based on 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene (BDTT) and linked-thieno[3,4-c]pyrrole-4,6-dione (LTPD). This polymer uses alkyl-substituted thiophene as a bridge. The PBDTT-LTPD includes two TPD units in one repeating unit, which can enhance acceptor density in the polymer backbone and lower the highest occupied molecular orbital (HOMO) level. By contrast, variable alkyl substitutions in the thiophene-bridges ensure the subtle regulation of polymer properties. The solar cells based on PBDTT-LTPD display an open-circuit voltage (Voc) that exceeds 1 V, and a maximum power conversion efficiency (PCE) of 7.59% is obtained. This PCE value is the highest for conventional single-junction bulk heterojunction solar cells with Voc values of up to 1 V. Given that PBDTT-LTPD exhibits a low HOMO energy level and a band gap equivalent to that of poly(3-hexylthiophene), PBDTT-LTPD/phenyl-C61-butyric acid methyl ester may be a promising candidate for the front cell in tandem polymer solar cells.

Design, synthesis and electronic properties of push–pull–push type dye

Alkyne conjugated push–pull–push type dye where alkyne π-spacer and push units monitor the electronic properties of the dye.

Improved photovoltaic performance of a 2D-conjugated benzodithiophene-based polymer by the side chain engineering of quinoxaline

To investigate the influence of side chains of quinoxaline on the photovoltaic performances, a novel D–A-type polymer of PBDTDT(Qx-3)-T was synthesized and characterized, in which BDT-T, T and Qx-3 were used as the donor (D) unit, π-bridge and acceptor (A) unit, respectively.

Synthesis and properties of benzo[c]-, pyrrolo[3,4-c]-, and thieno[3,4-c]-pyrrole-4,6-dione copolymers

New π-conjugated alternating donor–acceptor polymers, based on functionalized imide acceptor structures with the 2,5-dithienylthieno[3,2-b]thiophene (DTT) donor structure, were successfully synthesized and their properties were studied.

Influence of β-linkages on the morphology and performance of DArP P3HT-PC61BM solar cells

Direct arylation polymerization (DArP) has emerged as a greener and more atom-efficient alternative to Stille polymerization. Despite the attractiveness of this method, DArP is known to produce β-linkages in polymers, which have β-protons available for activation. Here, we report the influence of the β-defect content in DArP poly(3-hexylthiophene) (P3HT) on the performance of bulk-heterojunction solar cells and the morphology of pristine polymers and their blends with PC61BM in thin films and compare with Stille P3HT containing 0% β-defects as a reference point. The optical and electrochemical properties as well as the hole mobilities of pristine polymers remain virtually the same when the amount of β-defects is limited to 0.75% or lower, as evidenced by UV-visible absorption spectra, cyclic voltammetry and space-charge-limited current (SCLC) mobility measurements. However, an increase of β-defect concentration to 1.41% significantly affects the oxidation onset, UV-visible absorption profile and hole mobility of P3HT. The key result of this study is that the photovoltaic performance of DArP P3HT with 0% β-defects is remarkably close to that of Stille P3HT, whereas the performance of DArP P3HT with 0-0.75% β-defects does not differ dramatically from that of Stille P3HT and could potentially be improved upon by individual optimization of the processing conditions.

Synthesis of N-alkyl pyrroles via decarboxylation/dehydration in neutral ionic liquid under catalyst-free conditions

A catalyst-free benign route toN-alkyl pyrroles by reacting aromatic, heteroaromatic or aliphatic aldehydes with 4-hydroxyproline in neutral ionic liquid under microwave irradiation is presented.

Influence of the Acceptor Composition on Physical Properties and Solar Cell Performance in Semi-Random Two-Acceptor Copolymers

Five novel semi-random poly(3-hexylthiophene) (P3HT) based donor-acceptor copolymers containing either thienopyrroledione (TPD) or both diketopyrrolopyrrole (DPP) and TPD acceptors were synthesized by Stille copolymerization, and their optical, electrochemical, charge transport, and photovoltaic properties were investigated. Poly(3-hexylthiophene-thiophene-thienopyrroledione) polymers P3HTT-TPD-10% and P3HTT-TPD-15% with either 10% or 15% acceptor content were synthesized as a point of reference. Two-acceptor polymers containing both TPD and DPP were synthesized with varying acceptor ratios to fine-tune electrooptical properties, namely, P3HTT-TPD-DPP (1:1) (7.5% TPD and 7.5% DPP), P3HTT-TPD-DPP (2:1) (10% TPD and 5% DPP), and P3HTT-TPD-DPP (1:2) (5% TPD and 10% DPP). The two-acceptor copolymers have broad and uniformly strong absorption profiles from 350-850 nm with absorption coefficients up to 8 × 10⁴ cm^-1 at ∼700 nm for P3HTT-TPD-DPP (1:2). This is reflected in the photocurrent responses of polymer:fullerene bulk heterojunction solar cells with PC₆₁BM as an acceptor where P3HTT-TPD-DPP (1:1) and P3HTT-TPD-DPP (1:2) have peak external quantum efficiency (EQE) values of 61% and 68% at 680 nm, respectively, and at 800 nm show impressive EQE values of 29% and 40%. Power conversion efficiencies in solar cells of P3HTT-TPD-10% and P3HTT-TPD-15% are moderate (2.08% and 2.22%, respectively), whereas two-acceptor copolymers achieve high efficiencies between 3.94% and 4.93%. The higher efficiencies are due to a combination of very large short-circuit current densities exceeding 16 mA/cm² for P3HTT-TPD-DPP (1:2), which are among the highest published values for polymer solar cells and are considerably higher than those of previously published two-acceptor polymers, as well as fill factors over 0.60. These results indicate that semi-random copolymers containing multiple distinct acceptor monomers are a very promising class of polymers able to achieve large current densities and high efficiencies due to favorable properties such as semicrystallinity, high hole mobility, and importantly broad, uniform, and strong absorption of the solar spectrum.