Excitation of Thin Cyanine Films via Energy Transfer from Si Substrate

Abstract

Energy transfer from an inorganic substrate to a cyanine molecule thin film has been investigated as an excitation method for organic luminescent devices. Cyanine molecule thin films were fabricated on a Si substrate using layer-by-layer assembly and were excited from the backside of the substrate to observe the luminescence. The luminescence intensity depends on the excitation power and excitation energy. Moreover, the dependence of the luminescence intensity on excitation energy clearly shows a profile similar to the absorption spectrum of Si. These results indicate that luminescence is not due to the direct optical excitation of cyanine by the light transmitted through the substrate but due to the energy transfer from the photoexcited carriers in the substrate. Our results demonstrate that such energy transfer can be used to excite organic molecules on inorganic substrates without energy matching between the electrodes and luminescent materials.

Electron transport in a silicon crystal observed by energy transfer luminescence

“…[23][24][25][26][27][28][29] The detail of the sample fabrication is available from the reference. 21) The thickness of the DTTCI thin film and the separation between the DTTCI film and the substrate were 6.7 nm and 6.0 nm, respectively, which were determined using a spectroscopic phase-modulated ellipsometer (HORIBA Jobin-Yvon UVISEL-TK9017TK).…”

“…It was confirmed by the excitation energy dependence of the luminescence intensity that the thin film was excited by the energy transfer from electrons inside the substrate. 21) packet traveling through the substrate has the same profile. Therefore, it is reasonable to fit the intensity profiles in this analysis using the Gaussian function.…”

“…It was confirmed by the excitation energy dependence of the luminescence intensity that the thin film was excited by the energy transfer from electrons inside the substrate. 21) (c) and 4(d), respectively. Because the laser that excited the backside of the substrate has the Gaussian profile, the electron wave packet traveling through the substrate has the same profile.…”

“…Recently, we reported the luminescence of a cyanine thin film on a silicon crystal due to energy transfer. 21) The electrons generated by laser light in the backside of the silicon substrate diffused through the crystal and excited the cyanine thin film via energy transfer in Jpn. J. Appl.…”

“…Figures 3(a)-3(c) show the image maps of peak intensities of the luminescence spectra measured at various excitation intensities. This luminescence was caused by that the electrons generated by light excitation of Si excite the DTTCI molecules through energy transfer during the relaxation process 21). The luminescence intensity is indicated by the color bar.…”