Conjugated Polymer Blend Microspheres for Efficient, Long-Range Light Energy Transfer

Abstract

Highly luminescent π-conjugated polymeric microspheres were fabricated through self-assembly of energy-donating and energy-accepting polymers and their blends. To avoid macroscopic phase separation, the nucleation time and growth rate of each polymer in the solution were properly adjusted. Photoluminescence (PL) studies showed that efficient donor-to-acceptor energy transfer takes place inside the microspheres, revealing that two polymers are well-blended in the microspheres. Focused laser irradiation of a single microsphere excites whispering gallery modes (WGMs), where PL generated inside the sphere is confined and resonates. The wavelengths of the PL lines are finely tuned by changing the blending ratio, accompanying the systematic yellow-to-red color change. Furthermore, when several microspheres are coupled linearly, the confined PL propagates the microspheres through the contact point, and a cascade-like process converts the PL color while maintaining the WGM characteristics. The self-assembly strategy for the formation of polymeric nano- to microstructures with highly miscible polymer blends will be advantageous for optoelectronic and photonic device applications.

Coupled Whispering Gallery Mode Resonators via Template‐Assisted Assembly of Photoluminescent Microspheres

“…In addition, the composition of the microsphere is silica with a refractive index of 1.46, the template in which the microsphere is embedded has a refractive index of 1.52, that could also result in some leakage/scattering losses at points where the microsphere is in contact with the template. Comparatively, Kushida et al studied conjugated polymer microspheres with similar sizes to what is being studied herein, one major difference was the refractive index for their polymer was significantly higher ( n = 1.8–2.0). Under much higher confinement, Q ‐factor was observed as high as 2200.…”

2,5‐Dimethoxybenzene‐1,4‐dicarboxaldehyde: An Emissive Organic Crystal and Highly Efficient Fluorescent Waveguide

“…The α was thus calculated to be 0.00120 dB/μm (Figure d). It is note that α value is relatively high in those of reported materials . The loss coefficient and red‐shift are mainly affected by the reabsorption during the propagation of the light along the crystal .…”

“…It is note that α value is relatively high in those of reported materials . The loss coefficient and red‐shift are mainly affected by the reabsorption during the propagation of the light along the crystal . In the region of short wavelength, the emission band overlaps with the absorption band of the crystalline powder and the excitation spectrum of the crystal (Figure a), which is harmful for the light propagation and results in a high loss coefficient.…”

“…The fluorescence intensities at the excited site (I in ) and the emitting tip (I out ) were recorded to calculate the optical loss coefficient by a single exponential fitting (I in /I out = Ae (À αX) , where X is the distance between the excited site and the emitting tip and α is the loss coefficient). [23][24][25][26][27][28][29] The α was thus calculated to be 0.00120 dB/μm (Figure 4d). It is note that α value is relatively high in those of reported materials.…”

“…[23][24][25][26][27][28][29] The loss coefficient and red-shift are mainly affected by the reabsorption during the propagation of the light along the crystal. [23][24][25][26][27][28][29] In the region of short wavelength, the emission band overlaps with the absorption band of the crystalline powder and the excitation spectrum of the crystal (Figure 3a), which is harmful for the light propagation and results in a high loss coefficient. In the region of long wavelength, the emission and absorption spectra of the crystal were well separated, which is beneficial to propagating light in the crystal and results in a low loss coefficient.…”