In this Letter, the effect of F4-TCNQ insertion at the anode/hole transport layer (HTL) interface was studied on joule heating and the lifetime of organic light-emitting diodes (OLEDs). Joule heating was found to reduce significantly (pixel temperature decrease by about 10 K at a current density of 40 mA/cm2) by this insertion. However, the lifetime was found to reduce significantly with a 1 nm thick F4-TCNQ layer, and it improved by increasing the thickness of this layer. Thermal diffusion of F4-TCNQ into HTL leads to F4-TCNQ ionization by charge transfer, and drift of these molecules into the emissive layer caused faster degradation of the OLEDs. This drift was found to reduce with an increase in the thickness of F4-TCNQ. © 2013 Optical Society of America.