A Wide-Bandgap Semiconducting Polymer for Ultraviolet and Blue Light Emitting Diodes†
Supporting information for this article is available on the journal's homepage at http://www.mcp-journal.de or from the author. The X-ray data of 2,10-dibromo-spirocyclohexane-1,6′-dibenzo[d.f][1,3] dioxepin have been deposited with the CCDC (deposition number CCDC186448).
Abstract
A novel wide-bandgap conjugated polymer (PDHFSCHD) consisting of alternating dihexylfluorene and rigidly twisted biphenyl units has been synthesized. The new fluorene-based copolymer composed of rigid twisting segments in the main-chain exhibits an optical bandgap of as high as 3.26 eV, and a highly efficient ultraviolet emission with peaks at 368 nm and 386 nm. An electroluminescence device from PDHFSCHD neat film as an active layer shows UV emission which peaks at 395 nm with a turn on voltage below 8 V. By optimizing the device conditions, a peak EL quantum efficiency of 0.054% and brightness of 10 cd · m−2 was obtained. Furthermore, blending a poly(dihexylfluorene) in the PDHFSCHD host gave pure blue emission peaking at 417 nm and 440 nm without long wavelength emission from aggregated species. Efficient energy transfer from PDHFSCHD to PDHF was demonstrated in these blended systems. Depressed chain-aggregation of PDHF in the PDHFSCHD host can correspond to pure blue emission behaviors.
The structure of the copolymer PDHFSCHD.
