面向IGZO-TFT-AMOLED像素电路设计的V_(TH)检测方法研究

Investigation of V_(TH) Detection Methods for AMOLED Pixel Circuit Design with IGZO-TFT

由于迁移率高、均匀性好、制备成本低等优势,铟镓锌氧化物薄膜晶体管(IGZO TFT)有望促成有源矩阵有机发光显示器件(AMOLED)的大规模量产。但是IGZO TFT存在阈值电压(VTH)漂移的问题,实用的AMOLED像素电路必须对VTH漂移进行补偿以实现较好的显示效果,而VTH的检测是AMOLED像素电路设计中的关键环节。本文系统研究了VTH检测方法,比较了放电法、充电法、偏置电流法补偿VTH的效果,研究了VTH检测时间和TFT寄生电容等参数的影响。研究结果表明:放电法不能精确地补偿负VTH漂移,充电法需要的VTH检测时间最长,偏置电流法能够达到的补偿精度最高。

Due to the high mobility,excellent uniformity over large area and low manufacturing cost,indium gallium zinc oxide thin film transistor（ IGZO TFT） is promising technology in promoting active matrix organic light emitting diode（ AMOLED） into mass production. However,threshold voltage（ VTH） shift of IGZO TFTs still exists,thus AMOLED pixel circuit is required to compensate VTHshift. VTHdetection method is essential in AMOLED pixel circuit design. This paper reviews typical VTHdetecting methods,namely the discharging method,charging method,and constant-current-biasing method. Simulations using Smart-Spiceare are carried out to compare the compensation efficiency. Also,the influences of VTHdetection time and TFT parasitic capacitance on different VTH detecting methods are comprehensively analyzed. It is shown that the discharging method can not accurately compensate negative VTHshift,the charging method requires the longest VTHdetection time,and the constant-current-biasing method has the highest compensation accuracy.