New approach of mechanochromic, thermally activated delayed fluorescence’ dyes consisting of “thioxanthenone derivative as an acceptor unit and two carbazole derivatives as the donor units” used as emitting layer in organic light-emitting diodes

Abstract

Two dyes containing of thioxanthenone derivative as an acceptor unit, were designed and synthesized for thermally activated delayed fluorescence (TADF) organic light emitting diodes (OLEDs). The photoluminescence (PL) spectra of hammered dyes were shifted and the dyes were mechanochromic. Ionization potential (IP) values of spin-coated dyes on the fluorine-tin oxide film ranged from −5.42 to −5.49 eV and the hole mobility values reached to 2.64 × 10−4 and 3.56 × 10−4 cm2 V−1s−1. Considering the higher values of the photoluminescence quantum yields (PLQYs) of spin-coated dyes on the solid films (16, 21%) that dispersed the dyes in a solution such as toluene (7, 3%), the aggregation induced emission enhancement (AIEE) phenomena were observed. In addition, the doped devices were fabricated based on 50 wt% poly (9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (TFB) as a host material through the solution process and physically evaporation deposition (PVD). In this study, the effect of utilizing 4, 4′, 4″-Tris [(3-methylphenyl) phenylamino]triphenylamine (m-MTDATA) as a hole transport layer was impressive and the exciplex forming was confirmed. Finally, the electroluminescence with CIE(x,y) of (0.2076,0.3634) was resulted for the device consisted of low turn on voltage of 4.43 V, maximum brightness of 21362.55 cd m−2, maximum current and power efficiency of 27.03 cd A−1 and 19.65 lm.W−1 and maximum external quantum efficiency of 9.71%.