材料科学
光电流
聚合物太阳能电池
带隙
光电子学
开路电压
有机太阳能电池
量子效率
吸收光谱法
太阳能电池
分析化学(期刊)
载流子
异质结
聚合物
电压
光学
有机化学
化学
复合材料
物理
量子力学
作者
Koen Vandewal,Abay Gadisa,Wibren D. Oosterbaan,Sabine Bertho,Fateme Banishoeib,Ineke Van Severen,Laurence Lutsen,Thomas J. Cleij,Dirk Vanderzande,Jean Manca
标识
DOI:10.1002/adfm.200800056
摘要
Abstract Photocurrent generation by charge‐transfer (CT) absorption is detected in a range of conjugated polymer–[6,6]‐phenyl C 61 butyric acid methyl ester (PCBM) based solar cells. The low intensity CT absorption bands are observed using a highly sensitive measurement of the external quantum efficiency ( EQE ) spectrum by means of Fourier‐transform photocurrent spectroscopy (FTPS). The presence of these CT bands implies the formation of weak ground‐state charge‐transfer complexes in the studied polymer–fullerene blends. The effective band gap ( E g ) of the material blends used in these photovoltaic devices is determined from the energetic onset of the photocurrent generated by CT absorption. It is shown that for all devices, under various preparation conditions, the open‐circuit voltage ( V oc ) scales linearly with E g . The redshift of the CT band upon thermal annealing of regioregular poly(3‐hexylthiophene):PCBM and thermal aging of poly(phenylenevinylene)(PPV):PCBM photovoltaic devices correlates with the observed drop in open‐circuit voltage of high‐temperature treated versus untreated devices. Increasing the weight fraction of PCBM also results in a redshift of E g , proportional with the observed changes in V oc for different PPV:PCBM ratios. As E g corresponds with the effective bandgap of the material blends, a measurement of the EQE spectrum by FTPS allows us to measure this energy directly on photovoltaic devices, and makes it a valuable technique in the study of organic bulk heterojunction solar cells.
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