添加剂调控P3HT薄膜形貌的机理及其光电性能

发布时间：2018-10-20 14:25

【摘要】：优化活性层形貌是提高聚合物太阳能电池器件效率的重要手段。而添加第三组分则是一种有效的方法,不仅能诱导聚合物结晶并提高其结晶度,同时可优化给体与受体的相分离尺度。本文将两种分子构型不同的聚苯乙烯和两种分子结构不同的液晶小分子作为添加剂,研究它们对聚(3-己基噻吩)/富勒烯(P3HT/PCBM)共混物薄膜的结晶与相分离行为以及P3HT结晶的影响。首先,将无规聚苯乙烯(aPS)和间规聚苯乙烯(sPS)与P3HT和PCBM以不同的比例共混,对该三元共混体系的相容性、薄膜形貌以及器件效率进行表征和分析,研究不同分子构型对P3HT/PCBM薄膜形貌及其太阳能电池器件效率的影响。结果表明:aPS或sPS与P3HT均不相容,当aPS含量低于50 wt%时,P3HT结晶度提高,分子链间距由1.63 nm增大至1.76 nm,且P3HT的结晶尺寸随着aPS含量增加而减小。在aPS/P3HT/PCBM三元共混物薄膜中,随aPS含量增加,薄膜的形貌由柱状结构变为层状结构,而PCBM则倾向于富集在aPS和P3HT的相界面。当sPS含量为3 wt%时,sPS能诱导P3HT结晶,进一步增加其含量,P3HT的结晶受抑制。当aPS含量为50 wt%时,aPS/P3HT/PCBM体系仍具有较高的光电转换效率(1.2%),而当sPS含量为3 wt%时,sPS/P3HT/PCBM体系的效率迅速衰减至0.6%。因此,聚苯乙烯的分子构型对P3HT/PCBM薄膜的形貌及其太阳能电池性能有较大影响。其次,将两种分子结构不同的4-氰基-4''-戊基三联苯(5CT)和2,2''-二辛基三联噻吩(8-TTP-8)液晶(LCs)与P3HT共混,将LCs/P3HT共混物的溶液旋涂于石英片上,在溶剂缓慢挥发的过程中,施加强度为1 T的磁场。在磁场作用下,液晶小分子优先自组装排列,然后作为模板诱导P3HT结晶形成纳米线。结果表明:经磁场处理后,两种液晶小分子均能形成有序结构,并进一步诱导P3HT结晶,增强P3HT分子链间的π-π堆叠,使P3HT形成更多的纳米线。纳米线的形成提高了P3HT薄膜的载流子迁移率。经磁场处理后,8-TTP-8/P3HT样品的载流子迁移率从纯P3HT薄膜的1.092×10-4 cm2/Vs提高至3.346×10-4 cm2/Vs,而5CT/P3HT样品的载流子迁移率则提高至3.114×10-4 cm2/Vs。与纯P3HT样品相比,共混物样品的载流子迁移率均提高了约3倍,说明在磁场作用下,液晶可诱导P3HT形成纳米线,并进一步提高薄膜的载流子迁移率。
[Abstract]:Optimizing the active layer morphology is an important means to improve the efficiency of polymer solar cell devices. The addition of the third component is an effective method, which can not only induce the crystallization and increase the crystallinity of polymer, but also optimize the separation scale between donor and recipient. In this paper, two kinds of polystyrene with different molecular configurations and two liquid crystal small molecules with different molecular structures were used as additives to study their effects on the crystallization and phase separation behavior and P3HT crystallization of poly (3-hexylthiophene) / fullerene (P3HT/PCBM) blend films. Firstly, random polystyrene (aPS) and syndiotactic polystyrene (sPS) were blended with P3HT and PCBM in different proportions. The compatibility, film morphology and device efficiency of the ternary blend were characterized and analyzed. The effects of different molecular configurations on the morphology of P3HT/PCBM thin films and the efficiency of solar cells were investigated. The results show that aPS or sPS are incompatible with P3HT. When the content of aPS is less than 50 wt%, the crystallinity of P3HT increases, the molecular chain spacing increases from 1.63 nm to 1.76 nm, and the crystalline size of P3HT decreases with the increase of aPS content. In aPS/P3HT/PCBM ternary blend films, with the increase of aPS content, the morphology of the films changed from columnar structure to layered structure, while PCBM tended to be enriched at the phase interface between aPS and P3HT. When the content of sPS is 3 wt%, sPS can induce the crystallization of P3HT and further increase its content. The crystallization of P3HT is inhibited. When the content of aPS is 50 wt%, the aPS/P3HT/PCBM system still has a higher photoelectric conversion efficiency (1.2%), while when the sPS content is 3 wt%, the efficiency of sPS/P3HT/PCBM system decreases rapidly to 0.6%. Therefore, the molecular configuration of polystyrene has great influence on the morphology of P3HT/PCBM films and the performance of solar cells. Secondly, the liquid crystalline (LCs) (LCP) and dioctyltrithiophene (8-TTP-8) liquid crystalline (LCs) of two different molecular structures of 4-cyano-4keto-pentyltriphenyl (5CT) and dioctyltrithiophene (8-TTP-8) were blended with P3HT, and the solution of LCs/P3HT blend was rotated on quartz wafer, and the solvent was slowly volatilized in the process of solvent volatilization. Apply a magnetic field with an intensity of 1 T. Under the action of magnetic field, liquid crystal molecules preferentially self-assemble and then act as templates to induce P3HT to crystallize to form nanowires. The results show that the two kinds of liquid crystal small molecules can form ordered structure after the treatment of magnetic field, and further induce the crystallization of P3HT, enhance the 蟺-蟺 stacking between the chains of P3HT molecules, and make P3HT form more nanowires. The formation of nanowires increases the carrier mobility of P3HT films. The carrier mobility of 8-TTP-8/P3HT films increased from 1.092 脳 10 ~ (-4) cm2/Vs to 3.346 脳 10 ~ (-4) cm2/Vs, of pure P3HT films, while that of 5CT/P3HT samples increased to 3.114 脳 10 ~ (-4) cm2/Vs. after magnetic field treatment. Compared with the pure P3HT samples, the carrier mobility of the blends was increased by about three times, indicating that the liquid crystal could induce P3HT to form nanowires under the action of magnetic field, and further improve the carrier mobility of the films.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.2;TM914.4

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