Recoverable residual image characteristics for n- and p-type low-temperature polycrystalline silicon (LTPS) thin-film transistor (TFT)-based organic light-emitting diode (OLED) displays using polyimide substrates were investigated. Unlike OLED displays using glass substrates, the n-type LTPS TFT-based OLED displays using a polyimide substrate showed inferior recoverable residual image characteristics compared to the p-type LTPS TFT-based OLED displays. By the analysis of the brightness relaxation characteristics of the residual image and technology computer-aided design (TCAD) simulations, an additional explanation for the recoverable residual image, related to the substrate, was identified. In the polyimide substrate, internal electric fields vary depending on the operation of the driving TFTs. Particularly, in the n-type LTPS driving TFTs, the direction of electric fields changes dramatically with brightness conditions. This can result in a drastic variation in charge behavior inside the polyimide substrate. Consequently, we found that when using a polyimide substrate rather than a glass substrate, the recoverable residual image characteristics of the OLED displays arise due to both the hysteresis characteristics of the LTPS TFTs and the charge generation and distribution in the polyimide substrate.
Bibliographical noteFunding Information:
Manuscript received April 8, 2019; accepted April 27, 2019. Date of publication May 1, 2019; date of current version June 26, 2019. This work was supported in part by LG Display, Co., Ltd., and in part by the Nano·Material Technology Development Program through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT under Grant 2018M3A7B4071517. The review of this letter was arranged by Editor L. K. Nanver. (Corresponding author: Hyun Jae Kim.) H. W. Hwang and K. W. Kim are with the School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, South Korea, and also with LG Display, Co., Ltd., Paju 10845, South Korea.
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All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering