非晶/结晶共混对聚合物光伏电池性能的影响

以局域规整聚（3-己基噻吩） （P3HT）制备了TiO₂/聚合物型双层结构光伏电池.利用稳态电流-电压测试和动态强度调制光电压谱，结合差热分析、吸收光谱和荧光光谱, 研究了非晶支化聚亚乙基亚胺（BPEI）作为P3HT膜层的添加成分对TiO₂/P3HT双层电池性能的影响.由于P3HT链的高结晶性，使得TiO₂/P3HT界面接触不好，导致电池性能差.当在P3HT中共混重量比W_BPEI/P3HT=1％—5％的BPEI时，电池性能得到显著改善；尤其是当W_BPEI/P3HT= 1％时，电池表现出近0.8V的开路电压和20μA/cm²的短路电流.结果表明BPEI对电池性能的影响不是源于P3HT-BPEI共混体系光学性能的变化，而主要是由于其改变了TiO₂/P3HT界面接触性能.BPEI对TiO₂/P3HT界面接触有两个相互竞争的影响，这取决于P3HT-BPEI共混体系的组成.一方面，通过降低P3HT的结晶度和增强与TiO₂表面的相互作用，改善P3HT链在TiO₂ 表面的附着；另一方面，当BPEI含量过高时，BPEI在TiO₂表面的附着量将增加，反而会阻碍P3HT与TiO₂表面的接触.良好的TiO₂/P3HT界面接触有利于提高激子的界面分离效率、光生电子的寿命和电池效率.本文结果有望为聚合物光伏电池性能的改善提供新的认识和方法. 关键词： 聚（3-己基噻吩） 二氧化钛 共轭聚合物 光伏电池

Amorphous/crystalline blend effects on the performance of polymer-based photovoltaic cells

Bilayer TiO₂/polymer photovoltaic cells are prepared by using regioregular poly（3-hexylthiophene） （P3HT） and branched poly（ethyleneimine） （BPEI） as an additive to P3HT. Influences of BPEI, an amorphous polymer, on the performance of bilayer TiO₂/P3HT cells are investigated by means of steady-state current-voltage measurements and dynamic intensity-modulated photovoltage spectroscopy, in combination with differential thermal analysis, UV-vis absorption and photoluminescence spectroscopy. Due to the high crystallinity of P3HT, bilayer TiO₂/P3HT cell exhibits a poor performance. As P3HT is blended with BPEI in the weight ratio of W_BPEI/P3HT=1％—5％, the performance of the devices is greatly improved; in particular, as W_BPEI/P3HT= 1%, the cell exhibits an open-circuit voltage of 0.8V and a short-circuit current of 20μA/cm². Results show that the influence of BPEI on the cell performance originates from the changed interfacial contact at TiO₂/P3HT interface rather than the varied optical properties of P3HT in P3HT-BPEI blend. BPEI imposes two competitive effects on interfacial contact between TiO₂ and P3HT, depending on the compositional structure of the blend. On one hand, BPEI improves the interfacial contact by reducing the crystallinity of P3HT and enhancing the interaction between P3HT and TiO₂. On the other hand, the interfacial contact will become worse with more BPEI chains accumulating on TiO₂ surface. A good contact at TiO₂/P3HT interface facilitates the access to a high exciton dissociation efficiency, a long lifetime of photogenerated electrons and further a high device efficiency. The results presented in this paper are expected to provide new insights and a novel strategy for improving the performance of polymer-based photovoltaic cells.