Efficient enhancement of polymer light emitting diode by inserting hole blocking layer

The triplet layer for the PLED was fabricated with ITO / PVK (77 nm) / CdS (115 nm) / Alq3 (84 nm) / Al (300 nm). The PLED devices were inserted in the CdS layer between the 77 nm PVK and 84 nm Alq3 absorbing the ambient light to reduce the reflection of the device. The maximum wavelength and luminescence intensity increase with the thickness of CdS. This indicated that the maximum wavelength shifted to a higher wavelength when the thickness of CdS increases. With the insertion of 115 nm of CdS layer between the PVK and Alq3, a lower turn on voltage can be obtained at 5.4 eV. Key words: Cadmium sulphide, photoluminescence, energy band gap, electrical conductivity, optical reflectance.