Electron blocking materials based on dimethyl-dihydrobenzofuran derivatives for highly efficient and long-lifetime blue fluorescent organic light-emitting diodes

Three dimethyl-dihydrobenzofuran derivatives, 7-(5-(dibenzo[b,d]furan-4-yl)- [1,1′-biphenyl]-3-yl)-12,12-dimethyl-7,12-dihydrobenzofuro[3,2-b]acridine (ΔΦΒΔΔβΑ), 7-(3,5-bis(dibenzo[b,d]furan-4-yl)phenyl)-12,12-dimethyl-7,12-dihydrobenzofuro[3,2-b]acridine (BDFPDDbA) and 13-(3,5-bis(dibenzo[b,d]furan-4-yl)phenyl)-5,5-dimethyl-5,13-dihydrobenzofuro[3,2-c]acridine (BDFPDDcA) were synthesized and applied as electron blocking layer (EBL) materials in blue fluorescent organic light-emitting diodes. These EBL materials exhibited excellent physical properties and good thermal stability, as evidenced by their high glass transition temperatures of above 120 °C. The blue emission peaks of all three EBL materials were around 466 nm. The high triplet energy levels of the three EBL materials were effective for increasing the external quantum efficiency (EQE). The device based on ΔΦΒΔΔβΑ showed a high EQE of 7.15% and a long lifetime of 277 h at 10 mA cm⁻². This lifetime was eight times longer than that of the 4,4′,4″-tris(N-carbazolyl)-triphenylamine-based device.