Dieterle Johannes, Broch Katharina, Hinderhofer Alexander, Frank Heiko, Gerlach Alexander, Schreiber Frank
Institut für Angewandte Physik , Universität Tübingen , Auf der Morgenstelle 10 , 72076 Tübingen , Germany.
J Phys Chem A. 2019 Aug 15;123(32):7016-7020. doi: 10.1021/acs.jpca.9b03980. Epub 2019 Aug 2.
In order to investigate the effects of intermolecular interactions on the optical properties of organic semiconductors, we employ mixing of the organic semiconductor perfluoropentacene (PFP; CF) with the wide band-gap organic semiconductor picene (PIC; CH). The binary mixed thin films are prepared by simultaneous coevaporation of PIC and PFP in vacuum. We determine the optical properties of the blends by differential reflectance spectroscopy (absorption) and photoluminescence (emission). PFP:PIC thin films are a rare case of mixed thin films with a known molecular packing. The formation of equimolar mixed domains with a crystal structure clearly different from that of the pure compounds is, in the case of nonequimolar blends, accompanied by pure domains of the excess compound. Due to the wide band gap of PIC, the effect of reduced intermolecular interactions between PFP molecules can be studied in detail without any direct contributions of PIC to the spectra. We find a strongly enhanced emission from PFP in the mixed thin films, which can be explained by decoupling. Real-time investigations of the absorption spectra during growth provide further insight into intermolecular coupling effects on optical properties.
为了研究分子间相互作用对有机半导体光学性质的影响，我们将有机半导体全氟并五苯（PFP；CF）与宽带隙有机半导体并四苯（PIC；CH）混合。二元混合薄膜是通过在真空中同时共蒸发PIC和PFP制备的。我们通过差分反射光谱法（吸收）和光致发光（发射）来确定混合物的光学性质。PFP:PIC薄膜是具有已知分子堆积的混合薄膜的罕见例子。在非等摩尔混合物的情况下，形成具有与纯化合物明显不同晶体结构的等摩尔混合域，同时伴有过量化合物的纯域。由于PIC的宽带隙，可以详细研究PFP分子间相互作用减弱的影响，而PIC对光谱没有任何直接贡献。我们发现在混合薄膜中PFP的发射强烈增强，这可以用解耦来解释。生长过程中吸收光谱的实时研究进一步深入了解了分子间耦合对光学性质的影响。
