Boron subphthalocyanine chloride crystalline thin film with a long range exciton diffusion length grown assisted by negative surface charges

Boron subphthalocyanine chloride (SubPc) crystalline thin film has been fabricated under the help of negative surface charges and its growth mechanism is discussed as well. This thin film is composed of triangular grains and shows turbostratic-graphite-like microscopic structure, which is verified by atomic force microscope and elliptical diffraction pattern in transmission electron microscopy. The exciton diffusion length of this crystalline thin film can reach to 95 ± 2 nm, which is 5.5 times larger than that of amorphous one fabricated by thermal evaporation. This long exciton diffusion length is comparable with the optical absorption depth in the visible light spectrum, which can be expected to enhance the performance of SubPc-based organic solar cells.