A New Poly-Si TFT Current-Mirror Pixel for Active Matrix Organic Light Emitting Diode

A new poly-Si thin-film-transistor (TFT) current-mirror-active-matrix-organic-light-emitting-diode (AMOLED) pixel, which successfully compensates for the variation of the threshold voltage as well as mobility in the excimer laser annealed poly-Si TFT pixel, is designed and fabricated. The OLED current
$(I_ OLED)$
of the proposed pixel does not depend on the operating temperature. When the temperature of pixel is increased from 27
$^circhboxC$
to 60
$^circhboxC$
, the
$I_ OLED$
of the new pixel circuit composed of four TFTs and one capacitor increases only about 1.5%, while that of a conventional pixel composed of two TFTs and one capacitor increases about 37%. At room temperature, nonuniformity of the
$I_ OLED$
in the proposed circuit was also considerably suppressed at around 9%. We have successfully fabricated a 1.2-in AMOLED panel
$(hbox96 times hbox96 times hboxred green blue)$
to evaluate the performance of the proposed pixel. A troublesome residual image caused by the hysteresis phenomenon of the poly-Si TFT was almost eliminated in the proposed AMOLED panel as a result of current programming.