Time-of-flight Measurement Of Hole-tunneling Properties And Emission Color Control In Organic Light-emitting Diodes

Hole transport properties of organic light‐emitting diodes (OLEDs) with a thin hole‐blocking layer (HBL) were evaluated by time‐of‐flight measurement. Electroluminescence (EL) spectra of OLEDs with various HBL thicknesses were also evaluated. The results clearly show that the time‐resolved photocurrent response and the emission color strongly depend on HBL thickness. This can be attributed to hole‐tunneling through the thin HBL. We successfully fabricated a white OLED by controlling the thickness of HBL.