A self-assembly monolayer (SAM), with phenyl-triethoxysilane (PTES), was used to modify the indium tin oxide anode for an organic light-emitting diode (OLED) in order to improve the OLED performance. The enhancement of OLED performance is attributed to the blockage of excessive hole injection by PTES, balancing the hole and electron injection numbers. The result indicates that the SAM process reaction time duration greatly affects the OLED performance outcomes. If the reaction time is too long, it will impact on the optical efficiency due to molecular aggregates accumulated on the SAM layers, thus reducing the performance of the OLEDs. The electrical and optical characteristics of the OLEDs are modeled by using the modified Shockley equation. Modified Shockley parameters are extracted to interpret the experimental data with excellent accuracy. Those parameters, both electrical and optical, can be used as the DC level modeling parameters for OLED product design simulations.