Diketopyrrolopyrrole‐based conjugated polymers and small molecules for organic ambipolar transistors and solar cells

The present highlight discusses major work in the synthesis of low bandgap diketopyrrolopyrrole ( DPP )‐based polymers with donor–acceptor–donor ( D–A–D ) approach and their application in organic electronics. It examines the past and recent significant advances which have led to development of low bandgap DPP ‐based materials with phenyl and thiophene as donors. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4241–4260     

Effects of different formulation PEDOT:PSS hole transport layers on photovoltaic performance of organic solar cells

In this study, the effects of the various types of PEDOT:PSS with different conductivities on the photovoltaic parameters of organic solar cells were investigated. The performances of five various commercially available PEDOT:PSS with formulations such as FET, PT2, PH1000, PH500 and PH were compared. It was observed that the device employing PH1000 as an interlayer between ITO and the active layer exhibited the highest photovoltaic performance as compared to other devices with FET, PT2, PH500 and PH. Copyright © 2015 John Wiley & Sons, Ltd.     

Designing spirobifullerene core based three-dimensional cross shape acceptor materials with promising photovoltaic properties for high-efficiency organic solar cells

The development of organic electron acceptor materials is one of the key factors for realizing high-performance organic solar cells (OSCs). Nonfullerene electron acceptors, compared to traditional fullerene acceptor materials, have gained much impetus owing to their better optoelectronic tunabilities and lower cost, as well as higher stability. Therefore, 5 three-dimensional (3D) cross-shaped acceptor materials having a spirobifullerene core flanked with 2,1,3-benzothiadiazole are designed from a recently synthesized highly efficient acceptor molecule SF(BR) ₄ and are investigated in detail with regard to their use as acceptor molecules in OSCs. The density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been performed for the estimation of frontier molecular orbital (FMO) analysis, density of states analysis, reorganization energies of electron and hole, dipole moment, open-circuit voltage, photo-physical characteristics, and transition density matrix analysis. In addition, the structure-property relationship is studied, and the influence of end-capped acceptor modifications on photovoltaic, photo-physical, and electronic properties of newly selected molecules ( H1-H5 ) is calculated and compared with reference ( R ) acceptor molecule SF(BR) ₄ . The structural tailoring at terminals was found to effectively tune the FMO band gap, energy levels, absorption spectra, open-circuit voltage, reorganization energy, and binding energy value in selected molecules H1 to H5 . The 3D cross-shaped molecules H1 to H5 suppress the intermolecular aggregation in PTB7-Th blend, which leads to high efficiency of acceptor material H1 to H5 in OSCs. Consequently, better optoelectronic properties are achieved from designed molecules H1 to H5 . It is proposed that the conceptualized molecules are superior than highly efficient spirobifullerene core-based SF(BR) ₄ acceptor molecules and, thus, are recommended to experiments for future developments of highly efficient solar cells.     

Morphology optimization in ternary organic solar cells

Ternary organic solar cells have drawn great attention because the highest power conversion efficiencies have reached ~12%, showing a promising prospect for the future applications. However, most reported ternary solar cells focus on the increase of light absorption and the optimization of energy alignment, but ignore the importance of morphology. Herein, we summarize the morphology optimization on the ternary blends with different structural aspects, such as controlling crystallinity, crystal orientation, domain size, and domain purity. Furthermore, the fundamental mechanism of ternary solar cells which is related to the morphology has been described. The efforts here will provide a guiding role for the morphology optimization on the ternary solar cells in the future.     

Synthesis of new di-anchoring organic sensitizer based on quinoxaline acceptor for dye-sensitized solar cells

New quinoxaline-based organic sensitizer bearing di-anchoring group for dye-sensitized solar cells (DSSCs) was synthesized from diethyl 4,5-diaminophthaltate, in which was prepared under mild condition by using Takehito’s method. The synthesized sensitizer was compared with mono-anchoring sensitizer through absorption spectra, emission spectra, J-V curve, and IPCE spectra, indicating the di-anchoring group leads to a noticeable improvement of J_sc value owing to more efficient intramolecular charge transfer and channel number increment.     

基于Cz-DPP不对称D-A结构新型有机小分子光伏材料的合成与性质

本文设计合成了一系列以咔唑(CZ)和吡咯并吡咯二酮(DPP)为基本结构单元的D-A结构的新型小分子材料,并对其进行了一系列的性能表征.合成的材料以咔唑作为给电子单元,吡咯并吡咯二酮作为吸电子单元,采用三键作为π桥,并引入4-氟苯基、4-氰基苯基和4-甲氧基苯基作为末端取代基团对材料进行修饰.其中材料CZBTDPPF和CZBTDPPO因分别具有1.85和1.79 eV的较窄带隙而分别获得了相对较高的的光电转化效率(1.97%和1.91%).由此可见,引入4-氟苯基和4-甲氧基苯基作为末端取代基团对于延长材料共轭结构、拓宽材料吸收从而实现材料光伏性能的提升具有重要的作用.     

Novel small oligothiophene molecules with phenylene and naphthalene cores as promising absorber materials for organic solar cells

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Linkage position influences of anthracene and tricyanovinyl groups on the opto-electrical and photovoltaic properties of anthracene-based organic small molecules

Anthracene-based small molecules incorporating an electron accepting tricyanovinyl (TCV) group was prepared to investigate the linkage position influences of the anthracene and TCV groups on the opto-electrical and photovoltaic properties of the molecules. The maximum absorptions of the anthracene-based molecules incorporating the TCV group at the phenyl group of the triphenylamine unit (TCV-TpaA_9,10T, TCV-TpaTA_9,10T, and TCV-TpaA_2,6T) or at the thiophene unit (TpaA_9,10T-TCV, TpaTA_9,10T-TCV, and TpaA_2,6T-TCV) were found to be dependent on the linkage position of the anthracene unit. The HOMO energy levels of the molecules containing TCV group at the phenyl group of the triphenylamine unit were deeper than those of the molecules containing TCV group at the thiophene unit. The solution processed small molecule organic solar cells (SMOSCs) prepared with the structure of ITO/PEDOT:PSS/TCV-TpaA_9,10T or TCV-TpaA_2,6T or TpaA_2,6T-TCV:PC₇₁BM (2:1 wt %)/LiF/Al exhibited a maximum energy conversion efficiency of 1.04%, 1.67%, and 1.95%, respectively, under AM 1.5 irradiation (100 mW cm⁻²).     

Ethynyl-linked perylene bisimide based electron acceptors for non-fullerene organic solar cells

Star-shaped electron acceptors based on perylene bisimide as end groups and spiro-aromatic core linked with ethynyl units were developed for nonfullerene solar cells. Ethynyl linkers are able to improve the planarity of conjugated backbone, resulting in enhanced electron mobility and power conversion efficiency in solar cells.     

Synthesis and characterization of benzobisthiazole based polymers as donor materials for organic solar cells

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