High Efficiency Up-Converting Single Phase Elastomers for Photon Managing Applications

Optically active materials able to up-convert the frequency of the incident radiation can be used to enhance the performance of photovoltaic and photocatalityc cells, recovering sub-bandgap photons not directly absorbed by the devices. Actually, sensitized up-conversion (SUC) based on multi-component organic systems is the most promising approach for these photon energy managing processes, being efficient also at the solar irradiance. However, applications of SUC on real devices have not been yet accomplished because its conversion yield usually drops dramatically in the solid state where the low dye mobility inhibits the diffusion controlled mechanisms ruling SUC photophysics. To overcome this limit, we prepared a single-phase elastomer (poly-butylacrilate) doped with proper dyes (platinum (II) octaetyl-porphyrin and 9,10-diphenylanthracene) to fabricate an efficient photon up-converting material. Thanks to the residual molecular diffusion provided by the soft host, and to the quenching reduction of involved metastable electronic excited-states in a solid environment compared to a liquid one, we obtained a record SUC yield of 17% at the solid state. SUC efficiency has been studied as function of the excitation power and sample temperature, elucidating the photophysical processes at the base of the high observed yield and assessing the guidelines for the fabrication of technologically appealing low power up-converting materials.