Performant flexible luminescent solar concentrators of phenylpolysiloxanes crosslinked with perylene bisimide fluorophores†
In this work, flexible 5 × 5 cm2 luminescent solar concentrators (LSCs) were prepared by integrating a reactive perylene bisimide fluorophore (FC546) into a polysiloxane network. The N,N′-diallyl units of FC546 and the Si–H groups of a linear (methylhydrosiloxane)phenylmethylsiloxane chain (HMP-502) enabled covalent network formation via a hydrosilylation reaction (OPSB-FC546). Two approaches were followed. In the first, five LSC1 devices were prepared by mixing different amounts of OPSB-FC546 containing 0.05 wt% FC546 with a two-component polysiloxane resin bearing Si–H and Si–vinyl groups. After curing, materials with 0, 50, 100, 150 and 200 ppm of FC546 were obtained. In the second approach, five LSC2 slabs with equal FC546 content were obtained by reacting FC546 with different amounts of HMP-502 to adjust the desired fluorophore content before incorporation into the two-component polysiloxane resin with a constant OPSB-FC546/resin ratio. Solid-state NMR experiments revealed that the OPSB-FC546 content in LSC1 strongly affected the molecular mobility of the system, i.e., leading to a decreased crosslink density compared to LSC2. The higher crosslinked network conferred higher thermal and light stability to LSC2, as evidenced by Evolved Gas Analysis with mass spectrometric detection. LSC1 and LSC2 exhibited spectroscopic profiles typical of perylene bisimide fluorophores with a maximum quantum yield of about 80% for LSC2, possibly due to the more rigid polymer network. A maximum photon external efficiency (ηext) of 5.7% was gathered from LSC2 flanked by a maximum device efficiency (ηdev) of about 0.5%, which was superior to the values recently reported for other flexible LSC systems with similar sizes.