Blended organic thin films have been studied during the last decades due to their applicability in organic solar cells. Although their optical and electronic features have been examined intensively, there is still a lack of detailed knowledge about their growth processes and resulting morphologies, which play a key role in the efficiency of optoelectronic devices such as organic solar cells. In this study, pure and blended thin films of copper phthalocyanine (CuPc) and the Buckminster fullerene $\left({\mathrm{C}}_{60}\right)$ were grown by vacuum deposition onto a native silicon oxide substrate at two different substrate temperatures, 310 and 400 K. The evolution of roughness was followed by in situ real-time x-ray reflectivity. Crystal orientation, island densities, and morphology were examined after the growth by x-ray diffraction experiments and microscopy techniques. The formation of a smooth wetting layer followed by rapid roughening was found in pure CuPc thin films, whereas ${\mathrm{C}}_{60}$ shows a fast formation of distinct islands at a very early stage of growth. The growth of needlelike CuPc crystals losing their alignment with the substrate was identified in co-deposited thin films. Furthermore, the data demonstrate that structural features become larger and more pronounced and that the island density decreases by a factor of four when going from 310 to 400 K. Finally, the key parameters roughness and island density were well reproduced on a smaller scale by kinetic Monte Carlo simulations of a generic, binary lattice model with simple nearest-neighbor interaction energies. A weak molecule-substrate interaction caused a fast island formation and weak interaction between molecules of different species was able to reproduce the observed phase separation. The introduction of different same-species and cross-species Ehrlich-Schwoebel barriers for interlayer hopping was necessary to reproduce the roughness evolution in the blend and showed the growth of CuPc crystals on top of the thin film in agreement with the experiment.

中文翻译：

---

相分离的酞菁-富勒烯共混物的薄膜生长：组合的实验和计算研究

由于混合有机薄膜在有机太阳能电池中的适用性，近几十年来已经对其进行了研究。尽管已经对其光学和电子特征进行了深入研究，但仍缺乏有关其生长过程和形成的形貌的详细知识，这对光电器件（如有机太阳能电池）的效率起着关键作用。在这项研究中，纯铜和混合铜酞菁（CuPc）和Buckminster富勒烯薄膜$（{\mathrm{C}}_{60}）$通过在两个不同的基板温度310和400 K上真空沉积到天然氧化硅基板上来生长这些金属。粗糙度的发展是通过原位实时x射线反射率进行的。生长后，通过X射线衍射实验和显微镜技术检查晶体取向，岛密度和形态。在纯CuPc薄膜中发现形成光滑的润湿层，然后迅速粗糙化，而${\mathrm{C}}_{60}$显示了在成长的早期阶段就迅速形成了独特的岛屿。在共沉积的薄膜中发现了针状CuPc晶体的生长，失去了与基底的排列。此外，数据表明结构特征变得更大，更明显，并且当从310 K变为400 K时，岛密度降低了四倍。最后，通过动力学，可以在较小规模上很好地再现关键参数的粗糙度和岛密度。具有简单近邻相互作用能的通用二元晶格模型的蒙特卡洛模拟。弱的分子与底物的相互作用导致快速的岛形成，并且不同物种的分子之间的弱相互作用能够重现观察到的相分离。