It depends: I've got a Samsung S II with OLED and it doesn't show any flickering. But also a later Samsung also with OLED from all I can tell, and it does, and

It depends: I've got a Samsung S II with OLED and it doesn't show any flickering. But also a later Samsung also with OLED from all I can tell, and it does, and sat together with someone else trying to figure out what's going on. My interpretation is that early OLED displays were always running 100% duty cycle, but instead would lower the current through each pixel for lowering the brightness (when dimming the S II very low (and adapt your eyes), you can start seeing artifacts, i.e. pixels being lit up less precise because they are in fact using the lowest few values available of the current range). For later phones it appears Samsung added a PWM on top of it, so as to be able to dim the display independent of the pixel currents, perhaps to get rid of these artifacts in low brightness settings, or possibly because this might be a bit more power efficient. What can be done, apparently (as my friend found out searching the internet), if you've got root, is to install a kernel driver to set the PWM duty cycle to 100% and instead use the old per-pixel dimming approach. I haven't bothered (not using my phones enough) but something potentially worthwhile to do if you use your device for a lot of (book) reading.