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Wootever

martin
Voltage supply is needed for the transimpedance amplifier, but the power consumption is very low, a single 9V battery probably lasts for months/years.

Edit:
Here are a few example photos of a basic OPT101 photosensor:

Galaxy S8 AMOLED PWM on 10cd/m2:

martin
The transimpedance amplifier converts current from the photodiode to a voltage usable by the oscilloscope (it basically amplify the signal for a more stable output).

The advantage of a combined/embedded design:
The integrated combination of photodiode and transimpedance amplifier on a single chip eliminates the problems commonly encountered in discrete designs, such as leakage current errors, noise pick-up, and gain peaking as a result of stray capacitance.

Hello, i'm using a similar setup with the Hantek 6022BL and a OPT101 (https://www.ebay.com/itm/232458733138).
This chip includes a photodiode with a transimpedance amplifier which greatly simplifies the schematic needed:

For the software i would suggest the great PcScope made by Fabio1963 (https://www.dropbox.com/sh/qieod71ucovd6we/AADJvoBmMZNcR0kFB8ysS7vSa?dl=0).

KM Do you think it could be ported to other AMOLED devices, too?

Probably yes, the AID (AMOLED intervall driving) dimming mechanism they are implementing is actively used since the Galaxy S3. Although the implementation itself may vary (especially Exynos vs. Qualcomm).
Unfortunately this is exclusively used by Samsung, other AMOLED Panel devices might use a different approach or a panel built-in solution.

We probably need a complete AMOLED datasheet of a recent panel to fully understand those settings.

KM Do you know why there still is this small 60 Hz flicker? Does it do anything important?

I can only guess, it might be used as a burn-in protection / panel longevity method.

About the low brightness deterioration:
What we can see on especially low brightness is called mura defects. Those are small irregularities / deviations caused by the oled production process.
The PWM effect is also used to mask those mura defects, apart from stabilizing the color temperature and grayscale linearity (although less noticeable then the mura defects).