Perpustakaan Digital ITB

Conjugated polymer is a class of novel semiconducting materials with unique optic and electronic properties, which has considerable potential for application in optoelectronic devices, such as photovoltaic and light emitting devices. Though the basic working principles of those devices have been much reported elsewhere, the working characteristics is still not well understood for improving their working performances. Recently, there is considerable interest in the development of white polymer Light Emitting Diode (WPLED), which generates white light emission for new generation of lighting technology. This Master project report describes the research result conducted to understanding the working characteristics and the underlying physical process of WPLED.An approach used for studying the generation of white light emission in this work is using the blending of the red emissive polymer and blue emissive polymer. This approach offers low cost fabrication because of its simplicity in fabrication process in comparison to other multi-cells and layers approaches. Poly(9,9-dioctylfluorene) (PFO) were used as the blue emissive polymer, whereas poly (2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene) (MEHPPV) were used as the red emissive polymer. The emission spectrum of those polymers blend would also cover the green region. WPLED with various blending ratio have been fabricated, i.e. 0,2 %, 0,4%, 0,6%, 0,8%, and 1% weight percentage of MEH-PPV to PFO. Their emission spectra and working characteristics, i.e. Iph-V and J-V curves, have been also investigated. The light emission of the fabricated WPLEDs was unexpectedly dominated by the light emission from MEH-PPV. In order to understand these WPLED characteristics, unipolar devices, namely Hole-Only (HO) and Electron-Only (EO), were fabricated and their working characteristics were investigated. The experimental results were analyzed using a modified model of space charge limited cur-rent (SCLC)in order to understand the charge carrier injection and transport processes responsible for the observed emission and working characteristics.