photo diode or photo transistor?

Other Hardware General Electronics
1

Hi,
Short question:
Regarding sensitivity, which one to prefer, photo diode or photo transistor?

2

They, probably, have close sensitivity for most application. The same time I'd expect better quality (sensitivity, noise level, speed) from single function device, diode, because of technological differences in manufacturing optoelectronics and transistors, which also divided in subcategory.

3

While there are always exceptions, as a general rule photo-diodes have faster response times, and photo-transistors exhibit more sensitivity since they include some amplification.

4

photo-transistors exhibit more sensitivity

This is not quite correct, probably it'd apply for Responsivity:
Photodiode - Wikipedia Sensitivity is defined by noise floor:
Sensitivity (electronics) - Wikipedia

5

While all the responses were great the OP didn't specify an application. Without specifics the question is difficult to answer...

Doc

6

Magician:

photo-transistors exhibit more sensitivity

This is not quite correct, probably it'd apply for Responsivity:
Photodiode - Wikipedia Sensitivity is defined by noise floor:
Sensitivity (electronics) - Wikipedia

Yep, you are correct. I was thinking more in terms of direct reading with an ADC. In that case the amplification of the transistor would result in more apparent sensivity, without amplification, the diode's sensitivity would be buried in the resolution noise of the ADC.