Organic Light-emitting Diodes Based On Silane Derivatives

After the first report about white organic light-emitting diodes by J.Kido and hiscoworkers since ca.15years ago, WOLEDs have attracted considerable attention dueto their great potential application in flat-panel displays. Furthermore, WOLEDs arepromising candidates for next-generation, energy-saving and large-area solid-statelighting sources. Concerning today’s world oil crisis and the fact that ca.20%of theelectricity generated on our planet is consumed by lighting, it’s of tremendoussignificance in developing highly efficient and environmental-friendly WOLEDs.Meanwhile, according to the white synthesis principle, to obtain excellent blueorganic light emitting diodes is the key in preparing a white oleds.Efficient blue organic light-emitting devices (oleds) have attracted muchattention, and improving the carrier balance is one of the most effective ways. Thenovel silane derivative DCzSiPy has a high T1of2.99eV and excellent charge carriertransporting characteristic, which facilitate the exothermic energy transfer to thedopants and the balanced carrier transporting in the emission layer, having potentialapplications in the blue OLEDs. We achieve optimized device ITO/MoO3(2nm)/DDCzSi(40nm)/DCzSiPy:FIrpic(8%,20nm)/Bphen(40nm)/LiF(0.8nm)/Al, theturn-on voltage is lower than3V, and the max current efficiency is19cd/A and powerefficiency is12lm/W. All is better than the performance of the traditional devicewhich involved mCP as host. These properties make it feasible to construct WOLEDswith simple structures and excellent performance.Novel tetraarylsilane-centered compounds (DCzSiPy and DDCzSi) have beenintroduced in fabricating efficient white organic light-emitting diodes (WOLEDs).Owing to its bipolar transportation characteristics of DCzSiPy, more balanced charge carrier injected into the emitting layer is achieved when it is selected as a single host.Here, double-carbazole-based material DDCzSi is used as hole-transporting layer(HTL) despite it is previously reported as a host for blue phosphorescent organiclight-emitting diodes. Highly efficient white phosphorescent organic light-emittingdiodes with single-host structures are demonstrated. The maximum current efficiencyis41.5cd/A and the maxmium power efficiency is39.4lm/W. CIEs of (0.41,0.47) at1000cd/m2, And the external quantum efficiency (EQE) roll-off from maximum tothat at5000cd/m2is only19.8%. By adjusting the proportion of the blue/orangeemitting layers, lower roll-off of14.7%is obtained. However, the maximum currentefficiency and power efficiency are reduced to36.7cd/A and33.2lm/W, respectively.CIE of (0.37,0.45) at10000cd/m2. We carried on the detailed analysis with the resultof the experiment. In summary, the use of a novel bipolar tetraarylsilane-centeredcompound DCzSiPy as host combined with DDCzSi which is also a noveldouble-carbazole-based compound as HTL allowed us to obtain highly efficientWOLEDs with the simpler single-host structures. Without any additional outcouplingtechnologies, the excellent performances with high current efficiency and powerefficiency and warm white light are achieved.