Abstract：Bulk heterojunction polymer solar cells based on the blend of MEH-PPV (poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene]) and PCBM (1-(3-mehyloxycarbonyl)propy1-phenyl[6,6]C61) were fabricated. The thickness of the active layer was controlled by changing the concentration of MEH-PPV∶PCBM (1∶4 in weight ratio) solution and spin speeds. Investigation of the effects of active layer thicknesses on the performance of the photovoltaic devices indicates that, when the spin-coated speeds are lower than 4 000 r·min-1 (round per minute), the open-circit voltage (Voc) remains almost unchanged at approximately 0.8 V, whereas the short-circuit density (Jsc) monotonically increases and the fill factor (FF) decreases slightly. The spin speeds that are higher than 5 000 r·min-1 rpm result in the Voc and Jsc both reduced. The Voc decreases from 0.78 V at the spin-speed of 5 000 r·min-1 to 0.67 V at 8 000 r·min-1, and the Jsc even decreases from 3.96 mA·cm-2 at 5 000 r·min-1 to 1.76 mA·cm-2 at 8 000 r·min-1. Jsc depends on the mutual impact of light absorption and carrier transport, while a contradicting effect from the two aspects is caused by varying the thickness of the active layer. The thicker the active layer, the more the excitons induced by light absorption. However, the build-in electric field becomes weaker and the pathway becomes longer for transporting the opposite charge carriers derived from exiciton separation to their corresponding electrodes at the same time, which makes the probability of charges collection by respective electrodes lower. With respect to the reduced Voc, it may be attributed to the increased proportion of exciton dissociation at the interfaces of MEH-PPV and PCBM with the relevant electrodes.
Key words：Polymer solar cells;Organic electronics;Exciton ionization
刘晓东，张福俊*，徐 征，赵谡玲，宋晶路，厉军明，宋丹丹，王永生 . 活性层厚度对体异质结聚合物太阳能电池性能的影响 [J]. 光谱学与光谱分析, 2010, 30(07): 1752-1755.
LIU Xiao-dong, ZHANG Fu-jun*, XU Zheng, ZHAO Su-ling, SONG Jing-lu, LI Jun-ming, SONG Dan-dan, WANG Yong-sheng. Influence of the Active Layer Thickness on the Performance of Bulk Heterojunction Solar Cell . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2010, 30(07): 1752-1755.
