P‐5: The Effect of Light‐shield Metal Layer on the IV Performance of the P‐type LTPS TFT

To integrate the function of finger‐print recognition within the OLED display panel, a light‐shield (LS) metal layer is incorporated underneath the buffer layer to form fingerprint image on the sensor based on the principle of puncture‐forming picture. Since the LS metal layer is underneath the LTPS TFT, it has some impact on the IV performance of the p‐type LTPS TFT. It has been shown that the floating LS layer causes the kink effect on the output characteristics curves of the p‐type TFT. Upon putting bias on the LS layer, the threshold voltage (V th ) shifting has been observed as well as the eliminating of the kink effect caused by the floating LS layer. The V th shifting effect may be explained by the substrate bias effect. The biased LS layer may increase the uniformity of the threshold voltage throughout the whole panel, gives better image quality.