This paper presents an Organic-Light-Emitting-Diode (OLED) equivalent circuit model with temperature coefficient and intrinsic capacitor. In order to precisely describe the OLED non-linear V-I characteristics at different junction temperatures, four parameters: maximum operating point, rated operating point, knee point, and temperature coefficient, are obtained from the OLED V-I curves to establish the improved Taylor series based OLED model. Furthermore, in order to perform the transient and AC simulations of the OLED drivers, the proposed model can be used to generate the V-I look-up table for the voltage-controlled-piecewise-linear (VPWL) behavior model for the time-domain and frequency-domain circuit simulations. Besides, the intrinsic capacitor of the OLED is voltage dependent and can be modeled with the piecewise-linear (PWL) behavior model to associate with the built VPWL behavior model for the OLED circuit simulations. Finally, the measured results are provided to compare with the modeled V-I curves, transient simulations, and AC simulations of the OLED.