Enhancing performance of planar molecule-based organic light-emitting diodes through deposition-rate optimization: Role of molecular packing

The authors report a systematic study on the influence of the film deposition rate on the performance of organic light-emitting diodes (OLEDs) based on planar bis(10-hydroxybenzo[h]qinolinato) beryllium. The lower the deposition rate is, the lower the electroluminescence efficiency is. The observation is attributed to easier formation of ordered Bebq2 aggregates for slower deposition rates, which result in higher electron mobility and lower photoluminescence (PL) efficiency. The faster degradation in both PL efficiency and electron injection accounts for the decreased device lifetime with the decrease in the deposition rate. The role of molecular packing in device performance is discussed.