The DC/AC Reliability of Pentacene-based OTFT

• Main Authors: Huang-Wei Pan, 潘皇維
• Other Authors: Hsiao-Wen Zan
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/90012163897659604515

碩士 === 國立交通大學 === 顯示科技研究所 === 95 === As organic thin film transistor has lots of advantage of low temperature fabrication、low cost and easy fabrication, it has good potential for application on flexible display、sensor、radio-frequency identification tags and other electronics. Although studies have been made on DC gate bias stress without drain bias, the drain bias and AC bias stress in actual operation of organic electronic device is unknown. So we focus on the study of DC gate bias with drain bias stress and AC bias stress in this thesis. First, in the DC gate bias stress without drain bias, the dependence of the threshold voltage shift on the stressing time is found to follow a stretched-exponential function. It is the same as the many recent researchs. When the drain bias is applied, the threshold voltage shift will decrease and be suppressed as the drain bias becomes more negative. Since the threshold voltage shift is proportional to the carrier density, as the drain bias becomes more negative, the carrier concentration in channel is decrease such that the threshold voltage shift is reduced. Therefore, a channel charge normalization factor was used to describe the influence of drain bias and to modify the conventional stretched-exponential function. The threshold voltage shift has strong frequency dependence-the higher frequency same duty ratio, the smaller the magnitude of threshold voltage shift. We used an simple RC equivalent circuit to simulate the device under negative pulsed bias stress. The RC circuit consists of the insulator capacitance Ci, pentacene capacitance Cs, and a effective pentacene resistance Rs for hole conduction and injection. Th effective channel carrier concentration considering the RC delay can successfully explain the dependence of threshold voltage shift on the pulse width of the stressing signal. The channel charge normalization also can be used as the DC bias effect modeto describe the influence of AC bias stress and to modify the conventional stretched-exponential function.