A light-emitting electrochemical cell (LEC) containing a hole-blocking layer of TmPyPB

Light-emitting electrochemical cells (LECs) are attractive candidates for low-cost light-emitting devices fabricated using solution-based processes on flexible substrates. Despite promising luminance levels, their efficiency needs further improvement to reach the requirements of the lighting market. Thereby one of the reasons for the efficiency loss is the imbalance between the electrons and holes typical within such devices. Here we present a hybrid solution-based device architecture comprising a thin film of 1,3,5-tri(m-pyridin-3-ylphenyl) benzene (TmPyPB) on top of the emissive layer of an LEC, targeting to improve the charge carrier balance within the device. The hybrid LEC in constant voltage mode shows an efficiency improvement of almost a factor of 2 compared to the reference device, reaching maximum luminous and current efficacy values of 4.2 lm W-1 and 5.4 cd A(-1), respectively. The measurements conducted using the hybrid and reference devices suggested a pronounced hole-blocking effect of the additional organic supporting layer as the origin of improvement.