Noncoherent Low-Power Upconversion in Solid Polymer Films

Abstract

Noncoherent low-power photon upconversion has been realized in solid thin films composed of an ethyleneoxide/epichlorohydrin copolymer doped with palladium octaethylporphyrin (PdOEP) and 9,10-diphenylanthracene (DPA). Selective excitation of PdOEP at 544 nm generates easily visualized DPA fluorescence in the blue with noncoherent light sources under ambient laboratory conditions. The incident excitation power dependence is quadratic in nature, exemplifying that sequential one-photon absorption by PdOEP leads to the sensitization of two triplet DPA chromophores, which in turn annihilate to produce the upconverted singlet DPA fluorescence. Time-resolved emission experiments confirm that the solid host facilitates these sequential bimolecular reactions leading to delayed DPA fluorescence; however, these processes are notably slower than the analogous photochemistry in fluid solution.

Photochemical upconversion: present status and prospects for its application to solar energy conversion

“…It has been determined that a crucial requirement for the matrix material is a low glass-transition temperature as the bimolecular interactions leading to the TET and TTA events require some residual diffusivity. 49 Consequently, most of the reported systems are based on soft 'rubbery' polymers. Up to now, TTA-UC has been demonstrated in several host matrices including, but not limited to, cellulose acetate, 50 polystyrene, 51 a copolymer of ethyleneoxide and epichlorohydrin, 49,52 polyurethane, 53,54 or poly-butylacrylate.…”

“…49 Consequently, most of the reported systems are based on soft 'rubbery' polymers. Up to now, TTA-UC has been demonstrated in several host matrices including, but not limited to, cellulose acetate, 50 polystyrene, 51 a copolymer of ethyleneoxide and epichlorohydrin, 49,52 polyurethane, 53,54 or poly-butylacrylate. 55 It was further shown that upconverting nanoparticles can be formed using the blending approach with different polymeric host media, including polystyrene 56 or poly-butylacrylate.…”

Kinetically controlled crystal growth approach to enhance triplet energy migration-based photon upconversion

“…Consequently, the majority of TTA-UC systems have been studied in solution 8,[11][12][13][14][15] or soft polymer matrices, [16][17][18][19][20] in which the TET and TTA processes are mediated by molecular diffusion and collision. Meanwhile, it is desirable for device applications that TTA-UC processes occur in the solid state without molecular diffusion.…”

Solar Spectrum Conversion for Photovoltaics Using Nanoparticles

“…low light intensity conditions, clearly of importance for outdoor operation. These chromophores (porphyins in this case) can be easily incorporated in a solid polymer so that the materials can be treated as thin film materials (Islangulov et al 2007). A problem with TTA upconverters is the spectral range.…”