P3HT/非富勒烯受体异质结有机太阳电池

非富勒烯受体材料在分子设计、光吸收及能级等多方面具有极其丰富的可调控性, 使得基于非富勒烯电子受体的本体异质结有机太阳电池(BHJ OSC) 近年得以迅速发展。P3HT聚合物作为被广泛研究的第二代有机半导体材料, 其价格便宜、具有较好的结晶性以及优异的载流子传输性能, 是经典的电子给体材料。本文综述了近年来以P3HT聚合物为给体、非富勒烯类有机化合物为电子受体的有机太阳电池研究进展, 探讨了P3HT/非富勒烯受体BHJ OSC中, 影响器件效率提升的关键因素, 以及电子受体优化设计方面的相应要求。对基于P3HT/非富勒烯受体 BHJ OSC器件的研究前景进行了展望。     

Diketopyrrolopyrrole‐Based and Tetracyano‐Bridged Small Molecules for Bulk Heterojunction Organic Solar Cells

Research on bulk heterojunction organic solar cells has rapidly grown over the past two decades, and device performance has reached power conversion efficiencies over 13 %. In this focus review, we highlight design strategies used for the development of diketopyrrolopyrrole‐ and tetracyano‐based molecular donors. We also describe how tetracyano‐bridged non‐fullerene acceptors can be developed by a click‐type [2+2]‐cycloaddition–electrocyclic ring‐opening reaction of acetylene‐bridged small molecules with tetracyanoethylene by simple modification.     

Naphtho[2,1‐b:3,4‐b′]dithiophene‐based Bulk Heterojunction Solar Cells: How Molecular Structure Influences Nanoscale Morphology and Photovoltaic Properties

Organic bulk heterojunction photovoltaic devices based on a series of three naphtho[2,1‐b:3,4‐b′]dithiophene (NDT) derivatives blended with phenyl‐C₇₁‐butyric acid methyl ester were studied. These three derivatives, which have NDT units with various thiophene‐chain lengths, were employed as the donor polymers. The influence of their molecular structures on the correlation between their solar‐cell performances and their degree of crystallization was assessed. The grazing‐incidence angle X‐ray diffraction and atomic force microscopy results showed that the three derivatives exhibit three distinct nanoscale morphologies. We correlated these morphologies with the device physics by determining the J–V characteristics and the hole and electron mobilities of the devices. On the basis of our results, we propose new rules for the design of future generations of NDT‐based polymers for use in bulk heterojunction solar cells.     

Effect of polydispersity on the bulk‐heterojunction morphology of P3HT:PCBM solar cells

Bulk heterojunctions (BHJs) based on semiconducting electron–donor polymer and electron–acceptor fullerene have been extensively investigated as potential photoactive layers for organic solar cells (OSCs). In the experimental studies, poly‐(3‐hexyl‐thiophene) (P3HT) polymers are hardly monodisperse as the synthesis of highly monodisperse polymer mixture is a near impossible task to achieve. However, the majority of the computational efforts on P3HT: phenyl‐C61‐butyric acid methyl ester (P3HT:PCBM)‐based OSCs, a monodisperse P3HT is usually considered. Here, results from coarse‐grained molecular dynamics simulations of solvent evaporation and thermal annealing process of the BHJ are shared describing the effect of variability in molecular weight (also known as polydispersity) on the morphology of the active layer. Results affirm that polydispersity is beneficial for charge separation as the interfacial area is observed to increase with higher dispersity. Calculations of percolation and orientation tensors, on the other hand, reveal that a certain polydispersity index ranging between 1.05 and 1.10 should be maintained for optimal charge transport. Most importantly, these results point out that the consideration of polydispersity should be considered in computational studies of polymer‐based OSCs. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 895–903     

Conjugated Oligothiophene Derivatives Based on Bithiophene with Unsaturated Bonds as Building Blocks for Solution‐Processed Bulk Heterojunction Organic Solar Cells

A new building block ATVTA that uses stiff carbon–carbon triple bonds (A) on 1,2‐di(2‐thienyl)‐ethene (TVT) has been developed. Oligothiophene derivatives S‐01 with a TVT unit, S‐02 with a 5,5′‐diethynyl‐2,2′‐dithienyl (AT2) unit and S‐03 with ATVTA were synthesized to compare their effects in a systematic study. Due to the better π‐conjugation extension of the TVT unit, S‐01 exhibits the most red‐shifted absorption profile among them, whereas S‐02 possesses the deepest HOMO level. While the HOMO level of S‐03 is down‐shifted by 0.02 eV relative to that of S‐01 , the alkyne linkages can effectively down‐shift the HOMO level. By replacing the terminal units of S‐03 with stronger electron acceptors, S‐04 and S‐05 exhibited broader absorption profiles and lower HOMO levels than those of S‐03 . Organic solar cells based on these molecules were fabricated and an S‐03 :PC₆₀BM (1:1, w/w) based device afforded the highest V_oc value of 0.96 V and a power conversion efficiency (PCE) of 2.19 %.     

基于聚合物给体/有机小分子/富勒烯受体的三元共混有机太阳能电池

成功构筑了基于聚合物给体P3HT/有机小分子TT-TTPA/富勒烯受体PC₆₁BM的三元共混有机太阳能电池. 共轭有机小分子TT-TTPA与PC₆₁BM有很好的相容性, 相分离很小. 溶剂退火和热退火时, 含量相对较少的TT-TTPA容易从P3HT相中脱离出来进入PC₆₁BM相, 增加P3HT的结晶空间, 从而提高P3HT的结晶度和相纯度. 通过引入少量的第三组分TT-TTPA, 制备的三元共混有机太阳能电池获得了4.41%的能量转换效率, 相对于P3HT/PC₆₁BM二元共混体系的效率(3.85%)提高显著.     

A‐D‐A Type Small Molecules Based on Boron Dipyrromethene for Solution‐Processed Organic Solar Cells

The unique properties of boron dipyrromethene (BODIPY) dyes including facile synthesis, high absorption coefficients, and delocalized molecular orbitals as well as excellent photochemical and thermal stability, make them promising as materials for organic solar cells. Accordingly, in this study three A‐D ‐A structural small molecules of BDTT‐BODIPY, FL‐BODIPY, and TT‐BODIPY have been synthesized, in which two BODIPY acceptor units are symmetrically conjugated to 4,8‐bis(5‐(2‐ethylhexyl) thiophen‐2‐yl)benzo[1,2‐b:4,5‐b]dithiophene (BDTT), 9,9‐dioctyl‐9H‐fluorene (FL), and thieno[3,2‐b]thiophene (TT) donor cores, respectively. The manipulation of the structural parameters significantly improves the performances of the BHJ OSCs, which show power conversion efficiencies of 4.75 %, 1.51 %, and 1.67 % based on [6,6]‐phenyl C₇₁‐butyric acid methyl ester (PC₇₁BM) as the acceptor material and BDTT‐BODIPY, FL‐BODIPY, and TT‐BODIPY as the donor materials, respectively.     

3D Metal–Organic Frameworks Based on Co(II) and Bithiophendicarboxylate: Synthesis,Crystal Structures,Gas Adsorption,and Magnetic Properties

Three new 3D metal-organic porous frameworks based on Co(II) and 2,2′-bithiophen-5,5′-dicarboxylate (btdc²⁻) [Co₃(btdc)₃(bpy)₂]·4DMF, 1; [Co₃(btdc)₃(pz)(dmf)₂]·4DMF·1.5H₂O, 2; [Co₃(btdc)₃(dmf)₄]∙2DMF∙2H₂O, 3 (bpy = 2,2′-bipyridyl, pz = pyrazine, dmf = N,N-dimethylformamide) were synthesized and structurally characterized. All compounds share the same trinuclear carboxylate building units {Co₃(RCOO)₆}, connected either by btdc^2– ligands (1, 3) or by both btdc^2– and pz bridging ligands (2). The permanent porosity of 1 was confirmed by N₂, O₂, CO, CO₂, CH₄ adsorption measurements at various temperatures (77 K, 273 K, 298 K), resulted in BET surface area 667 m²⋅g⁻¹ and promising gas separation performance with selectivity factors up to 35.7 for CO₂/N₂, 45.4 for CO₂/O₂, 20.8 for CO₂/CO, and 4.8 for CO₂/CH₄. The molar magnetic susceptibilities χ_p(T) were measured for 1 and 2 in the temperature range 1.77–330 K at magnetic fields up to 10 kOe. The room-temperature values of the effective magnetic moments for compounds 1 and 2 are μ_eff (300 K) ≈ 4.93 μ_B. The obtained results confirm the mainly paramagnetic nature of both compounds with some antiferromagnetic interactions at low-temperatures T < 20 K in 2 between the Co(II) cations separated by short pz linkers. Similar conclusions were also derived from the field-depending magnetization data of 1 and 2.