Effect of TPD films as electron blocking layer on EL spectrum

Abstract

In an organic thin film electroluminescence (OTFEL) device with an ITO/PPV/Alq:DCM1/A1 structure, a TPD layer was inserted between the PPV and Alq:DCM1 layers. A device without the TPD layer or with a 5-nm thick TPD layer operating at higher DC voltage (≥8 V) exhibited EL emission from both the PPV (513 nm) and Alq:DCM1 (591 nm) layers, however, a device with a 5-nm thick TPD layer operating at lower voltage (<7 V) or with a 10-nm thick TPD layer had an EL emission peak at 591 nm, implying that the TPD layer can effectively block electron transportation. Hence we can spatially control the carrier recombination zone and obtain different EL emissions by adjusting the thickness of the carrier blocking layer and the driven voltage.