Dependence of the photophysical properties of exciplex in the polymer blends on the composite ratios and excitation wavelengths

We investigate the dependence of the optical spectral properties of the exciplex in the polymer blend of Poly (9, 9´-dioctylfluorene-co-benzothiadiazole) (ADS133YE) and poly (9,9´-dioctylfluorene-co-bis-N, N´-(4-butylphenyl)-bis-N,N´- phenyl-l,4 - phenylenediamine) (ADS232GE) on the excitation wavelengths and on the composite ratios between these two materials. By controlling the excitation wavelength, the energy transfer can be optimized, which favors the formation of the exciplex on the interface between the two blend phases. Furthermore, changing the composite ratio acutally modifies the mophorlogy of the blend film, modifying the excited states on the interface and giving the microscopic insights into the mechanisms of the exciplex emission. These investigations are important for better understanding the physics of the heterojunction structures in the polymer blends and is thus helpful for the design of organic photovoltaic devices.