Technische Universität Ilmenau, Institut für Physik and Institut für Mikro- und Nanotechnologien, 98693 Ilmenau, Germany.
Phys Chem Chem Phys. 2013 Oct 21;15(39):16494-502. doi: 10.1039/c3cp42236d. Epub 2013 Aug 9.
Most high-performance organic solar cells involve bulk-heterojunctions in order to increase the active donor-acceptor interface area. The power conversion efficiency depends critically on the nano-morphology of the blend and the interface. Spectroscopy of the sub-bandgap region, i.e., below the bulk absorption of the individual components, provides unique opportunities to study interface-related properties. We present absorption measurements in the sub-bandgap region of bulk heterojunctions made of poly(3-hexylthiophene-2,5-diyl) as an electron donor and [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) as an electron acceptor and compare them with quantum-chemical calculations and recently published data on the external quantum efficiency (EQE). The very weak absorption of the deep sub-bandgap region measured by the ultra-sensitive Photothermal Deflection Spectroscopy (PDS) features Urbach tails, polaronic transitions, conventional excitons, and possibly charge-transfer states. The quantum-chemical calculations allow characterizing some of the unsettled spectral features.
大多数高性能有机太阳能电池都涉及体异质结,以增加活性施主-受主界面面积。功率转换效率取决于混合物和界面的纳米形态。亚带隙区域的光谱研究,即低于各个组件的体吸收,提供了研究与界面相关性质的独特机会。我们提出了由聚(3-己基噻吩-2,5-二基)作为电子给体和[6,6]-苯基-C61-丁酸甲酯(P3HT:PCBM)作为电子受体的体异质结在亚带隙区域的吸收测量,并将其与量子化学计算和最近发表的外部量子效率(EQE)数据进行比较。超灵敏光热偏转光谱(PDS)测量的深亚带隙区域的非常微弱吸收具有 Urbach 尾部、极化子跃迁、常规激子,以及可能的电荷转移态。量子化学计算允许表征一些未解决的光谱特征。