Influence of the size effect on the generation and transport of charge carriers of phthalocyanines

Abstract

In this work, on the surface of glass substrates with an ITO coating, solid phthalocyanine films with grain sizes of 40–50 nm were obtained by thermal evaporation in a vacuum, and nanowires with a cross-sectional area of ~ 5–7 nm and a thickness of 100 nm were synthesized by the method of gradient-temperature vapor deposition. The absorption spectra were measured in the visible range of the spectrum. It was found that the observed broadening of the bands and the shift of the peaks in the Q- and B-ranges in the absorption spectra of phthalocyanine nanowires are associated with the fact that the molecules in the nanowires are more densely packed compared to the films obtained by thermal evaporation, as a result of which their optical properties are complicated by intermolecular interactions. ITO/MPc/Al cells were prepared for photoelectrophysical measurements. The I–V characteristics of solid films and nanowires are measured. It is shown that in nanowires there is an increase in the maximum value of the I–V characteristic of phthalocyanines by 1.5 times and the open-circuit voltage by 0.1 V. The impedance spectra are measured. It was found that in nanowires, as compared to solid films, an increase (more than 10 times) in the effective mean free path of the charge, a decrease in the recombination resistance (by almost two orders of magnitude), and an increase in conductivity are observed. The results obtained can be used to improve the electrical transport characteristics of composite solar cells, organic light-emitting devices, and to develop sensitive elements for photoelectronic devices.