Consequences of hydrogen bonding on molecular organization and charge transport in molecular organic photovoltaic materials
作者:Benjamin M. Schulze、Nathan T. Shewmon、Jing Zhang、Davita L. Watkins、John P. Mudrick、Weiran Cao、Raghida Bou Zerdan、Anthony J. Quartararo、Ion Ghiviriga、Jiangeng Xue、Ronald K. Castellano
DOI:10.1039/c3ta13529b
日期:——
Reported is a systematic molecular structure–property relationship study to evaluate the consequences of dedicated H-bonding interactions between molecular electron donors on molecular assembly, absorption, charge collection, and performance in small-molecule bulk heterojunction organic photovoltaic devices. Three families of branched quaterthiophene donor chromophores have been synthesized with members that share nearly identical electronic and optical properties in the molecularly dispersed state but are either capable or incapable of self-association by hydrogen bonding (H-bonding). Phthalhydrazide-functionalized quaterthiophenes are H-bond “active” and show signatures of H-bond promoted assembly in solution (by 1H NMR) and in both neat and blended (with C60) films (by IR). Compared to control compounds with H-bonding “turned off”, the H-bonded derivatives show red-shifted thin film absorption (neat and as blends with C60), different colors as bulk solids, and increased decomposition and melt temperatures. Photovoltaic devices made from blends of H-bonded donor molecules with C60 as the electron acceptor show improved charge collection length and external quantum efficiency resulting in a more than two-fold enhancement in power conversion efficiency relative to non-H-bonding controls, from 0.49% to 1.04%. We anticipate this approach could be generalized to include other donor chromophores with lower optical gap to harvest more longer-wavelength photons and achieve higher power conversion efficiencies.
报告描述了一项系统的分子结构-性质关系研究,旨在评估分子电子供体之间专用氢键相互作用对小分子异质结有机光伏器件的分子组装、吸收、电荷收集和性能的影响。研究人员合成了三个支链四噻吩供体发色团家族,它们在分子分散状态下具有几乎相同的电子和光学性质,但能够或不能通过氢键(H键)进行自缔合。邻苯二甲酰肼官能化的四噻吩具有H键“活性”,在溶液中(通过1H NMR)以及纯薄膜和混合薄膜(与C60)中(通过IR)表现出H键促进组装的特征。与H键“关闭”的对照化合物相比,H键衍生物显示出红移薄膜吸收(纯薄膜和与C60的混合薄膜)、不同颜色的块状固体以及更高的分解和熔化温度。由H键供体分子与C60作为电子受体的混合物制成的光伏器件显示出更长的电荷收集长度和外部量子效率,与非H键对照相比,功率转换效率提高了两倍以上,从0.49%提高到1.04%。我们预计这种方法可以推广到其他具有较低光学间隙的供体发色团,以捕获更长的波长光子,实现更高的功率转换效率。