I created a visualization of how many OLEDs actually flicker and use PWM: https://www.sundiallabs.tech/pages/oled-flicker
The goal of my page is to explain how and why OLEDs flicker, and also describe how to properly measure OLED flicker. I've been doing lots of flicker measurements on OLEDs lately, and it can be confusing to get right. I've also seen lots of PWM test results on OLEDs that were not done completely correctly and end up underestimating the flicker depth. Incorrect results are especially common to see at high / moderate brightness.
The first visualization shows how the dimming works on mobile OLEDs, specifically modeled after the iPhone 17 Super Retina XDR OLED. It appears to use DC-dimming for some of the brightness range, then switch to PWM. This is done because most OLEDs can only be DC-dimmed to a certain point.
The second visualization explains why OLEDs need to be measured carefully. The basic idea is that if your measurement device is detecting light from multiple rows, the waveform will be "smeared" or averaged and the flicker will look less bad than it actually is. This averaging isn't what our eyes do (they form an image of the screen which preserves the flicker pattern). So ideally, we need to be measuring the flicker from a single row (or only a few adjacent rows).
This isn't a problem we have when measuring LCD PWM, since the entire screen is generally doing the same thing. It may be one reason why some of us (myself included) tolerate OLEDs less than LCDs: you have a spatially nonuniform temporal light modulation.
Here's an example of an iPhone 16 measurement I found online that greatly underestimates the flicker at 100% brightness:
In reality, the modulation depth on most OLEDs is going to be nearly 100% even at full brightness. I plan to make a post demonstrating this experimentally in the future.