Direct arylation synthesis of thienoisoindigo‐based low‐band‐gap polymer from asymmetric donor–acceptor monomer

Thienoisoindigo (TIG) moiety has been paid numerous attentions as an excellent acceptor building block in low‐band‐gap polymers. Herein, a new TIG‐dithiophene alternating copolymer (PTIG2T) was successfully synthesized from an asymmetric TIG‐based donor–acceptor (D‐A) monomer via the self‐condensation‐type direct arylation polymerization. PTIG2T exhibited the light absorption over 1000 nm owing to the intramolecular charge transfer in the thin film state, which corresponded to an optical band gap of 1.24 eV. The HOMO and LUMO levels of PTIG2T were determined to be −5.08 and −3.60 eV, respectively. Furthermore, the organic photovoltaic (OPV) with a PTIG2T/PC₆₁BM active layer achieved a power conversion efficiency (PCE) of 3.19%, which is one of the highest PEC achieved by OPVs with TIG‐based materials. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 430–436     

Exploring the synthesis and impact of end‐functional poly(3‐hexylthiophene)

In recent years, end‐functional poly(3‐hexylthiophene) (P3HT) has proven to be instrumental in the continued development and innovation within the broad conjugated polymer arena, enabling a variety of applications, particularly in organic electronics. The availability of P3HT with controlled molecular weights, low polydispersity, and importantly, a wide range of reactive end‐groups not only serves as a key building block for the preparation of conjugated block copolymers but also facilitates the development of hybrid nanocomposite materials via inorganic surface modification strategies. This Highlight focuses on the synthetic approaches to end‐functional P3HT and the impact of these systems in emerging technologies. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 831–841     

Ternary-organic photovoltaics with J71 as donor and two compatible nonfullerene acceptors

Recombining the advantages on photovoltaic parameters of two binary-organic photovoltaics (OPVs) into one ternary cell is an efficient strategy for selecting materials, in addition to the absorption spectra complementary among the used materials. The binary-OPVs with J71:BTP-4F-12 exhibit a power conversion efficiency (PCE) of 11.70%, along with a short-circuit-current-density (J_SC) of 23.61 mA cm⁻², an open-circuit-voltage (V_OC) of 0.841 V and a fill factor (FF) of 58.99%. Although the relatively low PCE of 10.92% and J_SC of 16.59 mA cm⁻² are achieved in J71:ITIC-based binary-OPVs, the V_OC of 0.935 V and FF of 70.40% are impressive compared with J71:BTP-4F-12-based OPVs. Optimal ternary-OPVs are achieved with J71:BTP-4F-12:ITIC as active layers by weight ratio of 1:0.48:0.72, delivering a markedly increased PCE of 13.05% with a V_OC of 0.903 V, a J_SC of 21.27 mA cm⁻² and a FF of 68.20%. An over 11.5% PCE improvement is obtained by recombining the advantages of binary-OPVs into ternary-OPVs with ITIC as photon harvesting reinforcing agent and morphology regulator. The good compatibility between BTP-4F-12 and ITIC provides large room to well optimize their relative content for achieving the well balanced three key photovoltaic parameters of ternary-OPVs.     

Synthesis and characterization of amantadinium iodoacetatobismuthate,a hybrid compound with mixed iodide–carboxylate anions

The amantadinium iodoacetatobismuthate(III) [C₁₀H₁₅NH₃·(CH₃)₂CO]₂[BiI_3.67(CH₃COO)_1.33] is a new hybrid halometallate with iodide ions partially replaced by oxygen-containing acetates to form stronger interaction between the anionic and cationic substructures. The title compound as well-shaped orange-red crystals was synthesized by a facile reaction in acetone solution in the presence of glacial acetic acid. The crystal structure of the compound consists of the infinite anionic chains [BiI_3.67(CH₃COO)_1.33]^2– and the countercations [C₁₀H₁₅NH₃·(CH₃)₂CO]+; according to the optical absorption data, the test compound is a semiconductor with a band gap of 2.06 eV.     

cis‐substituted tetraethynylporphyrin derivatives for small molecule organic solar cells

A 5,10‐Bis(phenylethynyl)‐15,20‐bis(triisopropylsilylethynyl)porphyrin (cis‐TIPSTEP) was synthesized by using phenylethynyl dipyrromethane and triisopropylsilylpropynal through scrambling of the ethynyl substituents. X‐ray crystallographic structures of cis‐TIPSTEP, 5‐phenylethynyl‐10,15,20‐tris(triisopropylsilylethynyl)porphyrin, and 5,10,15,20‐tetrakis(triisopropylsilylethynyl)porphyrin were determined in order to study the packing structure; cis‐TIPSTEP exhibited good π‐overlap and parallel π‐stacking structures. 5,10‐Bis(phenylethynyl)‐15,20‐bis(triisopropylsilylethynyl)porphyrinato magnesium (II) (Mg‐cis‐TIPSTEP) was synthesized for the use in small molecule organic solar cells, which gave power conversion efficiency of 1.5% with short‐circuit current density of 4.5 mA/cm², open‐circuit voltage of 0.83 V, and fill factor of 0.39. Copyright © 2013 John Wiley & Sons, Ltd.     

AFM study of advanced composite materials for organic photovoltaic cells with active layer based on P3HT:PCBM and chiral photosensitive liquid crystalline dopants

Advanced composite materials aimed for construction of organic photovoltaic cells have been studied by atomic force microscopy (AFM). The composites are based on poly(3-hexylthiophene) (P3HT), [6,6]-phenyl C₆₁-butyric acid methyl ester (PCBM) and two different chiral photosensitive liquid crystalline (LC) materials. The objective of the study was to examine the nanoscale morphology of the active layer without and after annealing at specific temperature. The preliminary results of AFM observation of the morphological changes done on the investigated composites revealed an increase in the surface ordering. The surface area ratio decreases for both studied composites, while the basic roughness parameters (S_a and S_q) have been found toughly dependent on the structure of the photosensitive LC dopant.     

Novel Donor-Acceptor Copolymers Based on Dithienosilole and Ketone Modified Thieno[3,4-b]thiophene for Photovoltaic Application

Two novel donor-acceptor （D-A） copolymers containing dithienosilole （DTS） donor unit and ketone modified thieno[3,4-b]thiophene （TT） acceptor unit, namely, poly{4,4＇-bis（2-ethylhexyl）dithieno[3,2-b：2＇,Y-d]silole-5,5＇-diyl- alt-l-（thieno[3,4-b]thiophen-2-yl）-2-ethylhexan-l-one} （PDTSTT） and poly{4,4＇-bis（2-ethylhexyl）dithieno[3,2- b：2＇,3＇-d]silole-5,5＇-diyl-alt- 1-（4,6-bis（4-ethylhexylthien-2-yl）thieno[3,4-b]thiophen-2-yl）-2-ethylhexan- 1-one} （PD- TSDTTT）, were synthesized for the application in polymer solar cells （PSCs）, and the effects of thiophene bridge on the structural geometry and photovoiltaie performance have been investigated. The polymer PDTSTT and PDTSDTTT have the electrochemical bandgaps of 1.54 and 2.02 eV, together with low-lying HOMO energy levels of-5.47 and -5.37 eV, respectively. Molecular geometry simulation result shows that compared with PDTSTT, the insertion of thiophene bridge in PDTSDTTT can well relieve the steric hindrance between the TT and DTS unit, as confirmed by the reduced dihedral angle between DTS and DTTT unit. Under the illumination of AM 1.5G, 100 mW/cm2, the PSC based on PDTSDTTT/PC61BM （1 ： 1, w ： w） demonstrates a power conversion efficiency of 1.0%, which is significantly improved in comparison with the device based on PDTSTT/PC61BM （1 ： 2, w ： w） under the same experimental condition. This is because the enhanced planarity and increased effective conjugation of the main chain in PDTSDTTT promote the more favorable morphology for charge transportation, although PDTSTT possesses the broader absorption band than PDTSDTTT.     

Development and Properties of Surfactant‐Free Water‐Dispersible Cu2ZnSnS4 Nanocrystals: A Material for Low‐Cost Photovoltaics

A simple, yet novel hydrothermal method has been developed to synthesize surfactant‐free Cu₂ZnSnS₄ nanocrystal ink in water. The environmentally friendly, 2–4 nm ultrafine particles are stable in water for several weeks. Detailed X‐ray diffraction (XRD) and high‐resolution transmission electron microscopy revealed the formation of single‐crystalline‐kesterite‐phase Cu₂ZnSnS₄. Elemental mapping by scanning electron microscopy/energy dispersive spectrometry corroborated the presence of all four elements in a stoichiometric ratio with minor sulfur deficiency. Finally, Raman spectroscopy ruled out the possible presence of impurities of ZnS, Cu₂SnS₃, SnS, SnS₂, Cu_2?xS, or Sn₂S₃, which often interfere with the XRD and optical spectra of Cu₂ZnSnS₄. X‐ray photoelectron spectroscopic studies of the as‐synthesized samples confirmed that the oxidation states of the four elements match those of the bulk sample. Optical absorption analyses of thin film and solution samples showed high absorption efficiency (>10⁴ cm^?1) across the visible and near‐infrared spectral regions and a band gap E_g of 1.75 eV for the as‐synthesized sample. A non‐ohmic asymmetric rectifying response was observed in the I–V measurement at room temperature. The nonlinearity was more pronounced for this p‐type semiconductor when the resistance was measured against temperature in the range 180–400 K, which was detected in the hot‐point probe measurement.     

Efficient interdigitated back‐contacted silicon heterojunction solar cells

We present back‐contacted amorphous/crystalline silicon heterojunction solar cells (IBC‐SHJ) on n‐type substrates with fill factors exceeding 78% and high current densities, the latter enabled by a SiN_x /SiO₂ passivated phosphorus‐diffused front surface field. V_oc calculations based on carrier lifetime data of reference samples indicate that for the IBC architecture and the given amorphous silicon layer qualities an emitter buffer layer is crucial to reach a high V_oc, as known for both‐side contacted silicon heterojunction solar cells. A back surface field buffer layer has a minor influence. We observe a boost in solar cell V_oc of 40 mV and a simultaneous fill factor reduction introducing the buffer layer. The aperture‐area efficiency increases from 19.8 ± 0.4% to 20.2 ± 0.4%. Both, efficiencies and fill factors constitute a significant improvement over previously reported values. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Exploiting the Bulk Photovoltaic Effect in a 2D Trilayered Hybrid Ferroelectric for Highly Sensitive Polarized Light Detection

Polarized light detection is attracting increasing attention for its wide applications ranging from optical switches to high‐resolution photodetectors. Two‐dimensional (2D) hybrid perovskite‐type ferroelectrics combining inherent light polarization dependence of bulk photovoltaic effect (BPVE) with excellent semiconducting performance present significant possibilities. Now, the BPVE‐driven highly sensitive polarized light detection in a 2D trilayered hybrid perovskite ferroelectric, (allyammonium)₂(ethylammonium)₂Pb₃Br₁₀ ( 1 ), is presented. It shows a superior BPVE with near‐band gap photovoltage of ca. 2.5 V and high on/off switching ratio of current (ca. 10⁴). Driven by the superior BPVE, 1 exhibits highly sensitive polarized light detection with a polarization ratio as high as ca. 15, which is far more beyond than those of structural anisotropy‐based monocomponent devices. This is the first realization of BPVE‐driven polarized light detection in hybrid perovskite ferroelectrics.