Highly soluble energy relay dyes for dye-sensitized solar cells

High solubility is a requirement for energy relay dyes (ERDs) to absorb a large portion of incident light and significantly improve the efficiency of dye-sensitized solar cells (DSSCs). Two benzonitrile-soluble ERDs, BL302 and BL315, were synthesized, characterized, and resulted in a 65% increase in the efficiency of TT1-sensitized DSSCs. The high solubility (180 mM) of these ERDs allows for absorption of over 95% of incident light at their peak wavelength. The overall power conversion efficiency of DSSCs with BL302 and BL315 was found to be limited by their energy transfer efficiency of approximately 70%. Losses due to large pore size, dynamic collisional quenching of the ERD, energy transfer to desorbed sensitizing dyes and static quenching by complex formation were investigated and it was found that a majority of the losses are caused by the formation of statically quenched ERDs in solution

Recent progress in lactam-based polymer semiconductors for organic electronic devices

Numerous polymer semiconductor materials with alternating electron donor-electron acceptor (D-A) structures have attracted immense attention because they exhibit excellent semiconductor performance and solution processability. These materials can be used for the fabrication of various lightweight and flexible electronic devices. In this review, we provide a brief overview of the structural features and important properties of lactams whose performance can be enhanced by introducing an acceptor in the design of D-A-type polymer semiconductor materials. The focus is on polymer semiconductor materials with lactams in their structures, such as diketopyrrolo[3,4-c]pyrrole, naphthalene diimide, isoindigo, 2,2-bithiophene-3,3-dicarboximide, and thieno[3,4-c]pyrrole-4,6-dione. The recent advances made in the field in the last 3 years are discussed. In addition, the application of polymers for the fabrication of organic electronic devices and the progress in the field are discussed.11Nsciescopu

Highly efficient polymer solar cells with a thienopyrroledione and benzodithiophene containing planar random copolymer

We synthesized and characterized a new low band-gap copolymer, PBTTFB, incorporating N-alkylthieno [3,4-c] pyrrole-4,6-dione (TPD) as the acceptor and benzodithiophene (BDT) and (2,5-difluorophenylene) dithiophene as the donor units with S...F and S...O non-covalent intramolecular interactions. The PBTTFB polymer replaced bis(dodecyloxy) benzo[c][1,2,5] thiadiazole (BT) in P1, a previously reported polymer, with 5-dodecyl-4H-thieno[3,4-c] pyrrole-4,6(5H)-dione and exhibited improved macromolecular planarity and molecular ordering of the molecular structure. UV-vis absorption, electrochemical properties, bulk-heterojuction (BHJ) film morphology, and molecular ordering as well as photovoltaic charaterization derived from PBTTFB were studied and analyzed to explore the effect of the thienopyrroledione unit instead of the benzodithiophene unit in the molecular backbone of the polymer. From photovoltaic charaterization, we obtained an enhanced J(sc) value of 14.51 mA cm(-2) from the PBTTFB polymer compared to the Jsc value of 10.54 mA cm(-2) from P1 due to improved macromolecular planarity. Furthermore, PBTTFB exhibited the highest PCE of 8.25% by adding DPE as a processing additive due to better interpenetration networks for improving charge transport and collection

A regioregular donor-acceptor copolymer allowing a high gain-bandwidth product to be obtained in photomultiplication-type organic photodiodes

Obtaining a photomultiplication-type organic photodiode with a high gain-bandwidth product is challenging. We show that a newly designed regioregular polymer enables the formation of a highly oriented face-on structure with a low trap density, leading to a high EQE and a fast response time. As a result, a gain-bandwidth product of over 4 × 105 Hz is achieved. © The Royal Society of Chemistry.1

Design and Synthesis of a New Non-Fullerene Acceptor for High-Performance Photomultiplication-Type Organic Photodiodes

Photomultiplication-type organic photodiodes (PM-OPDs) rely on acceptor molecules for both charge separation and efficient gain generation. Herein, a new non-fullerene acceptor is designed and synthesized by introducing thienylenevinylene (TV) groups into the conventional 2,2MODIFIER LETTER PRIME-[[6,6,12,12-tetrakis(4-hexylphenyl)-6,12-dihydrodithieno[2,3-d:2MODIFIER LETTER PRIME,3MODIFIER LETTER PRIME-dMODIFIER LETTER PRIME]-s-indaceno[1,2-b:5,6-bMODIFIER LETTER PRIME]dithiophene-2,8-diyl]bis[methylidyne(3-oxo-1H-indene-2,1(3H)-diylidene)]]bis[propanedinitrile] (ITIC) structure. The resulting TV-ITIC acceptor possesses not only extended pi-conjugation length, which leads to lower energy bandgap as well as deeper lowest unoccupied molecular orbital (LUMO) level, but also enhanced hydrophobic characteristics, owing to the increased volumetric portion of the aliphatic chain, which improves the miscibility with the donor polymer semiconductor, poly(3-hexylthiophene-2,5-diyl) (P3HT). Moreover, pristine TV-ITIC films consist of intrinsically well-ordered anisotropic crystallites, which are confirmed by 2D grazing incidence X-ray diffraction (2D-GIXD) analysis. All of these photophysical properties are beneficial for efficient exciton separation, electron trapping, and charge injection abilities of PM-OPDs compared to those obtained with conventional ITIC. Because of such synergetic contributions of TV-ITIC to the photomultiplication mechanism, the resulting optimized PM-OPD exhibits a high external quantum efficiency (>74,000%) and a large specific detectivity (>10(12) Jones). © 2020 Wiley-VCH GmbH1

Dual Responsive Dependent Background Color Based on Thermochromic 1D Photonic Crystal Multilayer Films

In this paper, we present dual responsive one-dimensional (1D) photonic crystal (PC) multilayer films that utilize a high-humidity environment and temperature. Dual responsive 1D PC multilayer films are fabricated on precoated thermochromic film by sequential alternate layer deposition of photo-crosslinkable poly(2-vinylnaphthalene-co-benzophenone acrylate) (P(2VN-co-BPA)) as a high refractive index polymer, and poly(4-vinylpyrollidone-co-benzophenone acrylate) P(4VP-co-BPA) as a low refractive index polymer. The thermochromic film shows a vivid color transition from black to white at 28 °C. Three different colors of thermochromic 1D PC multilayer films are prepared by thickness modulation of P(4VP-co-BPA) layers, and the films on a black background exhibit visible spectrum color only in a high-humidity environment (over 90% relative humidity (RH)). For the three films placed on a hands display, three different composite colors are synthesized by the reflection of light, including yellow, magenta, and cyan, due to the changing of backgrounds from black to white with temperature. Additionally, the films show remarkable color transitions with reliable reversibility. The films can be applied as anti-counterfeiting labels and can be used for smart decoration films. To the best of our knowledge, this is the first report of dual response colorimetric films that change color in various ways depending on temperature and humidity changes, and we believe that it can be applied to various applications

Sequential "click'' functionalization of mesoporous titania for energy-relay dye enhanced dye-sensitized solar cells

Energy relay dyes (ERDs) have been investigated previously as a mean to achieve panchromatic spectral response in dye-sensitized solar cells via energy transfer. To reduced the distance between the ERDs and energy-accepting injection dyes (IDs) on the surface of a mesoporous titanium dioxide electrode, the ERDs were immobilized adjacent to the IDs via a sequential functionalization approach. In the first step, azidobenzoic acid molecules were co-adsorbed on the mesoporous titanium dioxide surface with the ID. In the second step, the highly selective copper(I)-catalyzed 1,3-dipolar azide-alkyne cycloaddition "click'' reaction was employed to couple an alkyne-functionalized ERD to the azidobenzoic acid monolayer. The cycloaddition step in the mesoporous electrode was slowed dramatically due to reactants and catalysts forming agglomerates. In solar cell devices, the close proximity between the surface-immobilized ERD and energy-accepting squaraine sensitizer dyes results in energy transfer efficiencies of up to 91%. The relative improvement in device performance due to the additional ERD spectral response was 124%, which is among the highest reported. The sequential functionalization approach described herein is transferrable to other applications requiring the functionalization of electrodes with complex molecules

High-Efficiency Organic Photovoltaics with Two-Dimensional Conjugated Benzodithiophene-Based Regioregular Polymers

We synthesized and characterized two kinds of regioregular polymers that were based on thieno[3,4-b]thiophene as an electron-accepting unit and benzo[1,2-b:4,5-b′]dithiophene as the electron-donating unit with different side chain, alkylthio and alkyl thiophenes, named rr-PTBS and rr-PTB7-Th, respectively. Because of the partial introduction of the alkylthio thiophene side chain, rr-PTBS showed red-shifted absorption and a deeper HOMO level compared to those of rr-PTB7-Th. In addition, both rr-PTBS:PC71BM and rr-PTB7-Th:PC71BM blended films showed face-on orientations stronger than those of regiorandom PTB7-Th. However, the rr-PTB7-Th:PC71BM blended film showed a peak in the out-of-plane direction much weaker than those of rr-PTBS:PC71BM and PTB7-Th:PC71BM blended films. Moreover, the rr-PTBS:PC71BM blended film exhibited charge carrier mobility (μe/μh ∼ 1.01) much more balanced than that of the rr-PTB7-Th:PC71BM blended film (μe/μh ∼ 1.23). The bulk-heterojunction organic photovoltaic (OPV) device based on rr-PTBS and the 1,8-diiodooctane additive showed a high power conversion efficiency (PCE) of 8.68%, while the OPV device based on rr-PTB7-Th and the 1,8-diiodooctane additive showed a PCE of 7.04%. Finally, an OPV device using rr-PTBS, the diphenyl ether additive, and Micro Lens Film exhibited a short-circuit current (Jsc) of 19.72 mA/cm2, an open-circuit voltage (Voc) of 0.82 V, and a fill factor (FF) of 63.82%, thus resulting in a PCE of 10.31%. © 2017 American Chemical Society.

Synergistic Effects of Terpolymer Regioregularity on the Performance of All-Polymer Solar Cells

Random terpolymers with three different monomer units can provide broader light absorption than the most widely used donor-acceptor (D-A) alternating copolymers, but their electrical properties are often sacrificed by the randomly distributed monomers in the polymeric backbone that prevent efficient intermolecular π- π interactions. Here, we report the development of a regioregular terpolymer and demonstrate its importance in enhancing the power conversion efficiency (PCE) of all-polymer solar cells (all-PSCs). To investigate the impact of the monomer sequence and regioregularity in the terpolymer, we designed and synthesized two terpolymers (Ra-(D1-A-D2-A) random terpolymer and RR-(D1-A-D2-A) regioregular terpolymer) consisting of two electron-donating benzodithiophene (BDT) units with different side chains and one electron-withdrawing fluorinated thieno[3,4-b]thiophene (TT-F) unit. As a reference polymer, we also synthesized the D1-A alternating copolymer. The RR-(D1-A-D2-A) film exhibited stronger π- π stacking and a larger crystallite size than the D1-A and Ra-(D1-A-D2-A) films, resulting in 1 order of magnitude higher hole mobility than those of the other polymers. When blended with the P(NDI2HD-DTAN) polymer acceptor, the RR-(D1-A-D2-A)-based all-PSC yielded an outstanding PCE of 6.13%, which was superior to those of the D1-A-based all-PSCs (4.81%) and Ra-(D1-A-D2-A)-based all-PSCs (4.93%). These findings indicate that the synthesis of the regioregular terpolymer is a promising design strategy for the development of high-performance all-PSCs with improved optical and electrical properties. © 2019 American Chemical Society.1