Existence of input signal to LED at photodiode output
Connect a large value resistor between the output of the op amp and the V- input. This is a transimpedance amplifier configuration. You may have to add a small value capacitor in parallel with that resistor to keep the amplifier stable.

I am not sure of the intent of R1 which pulls the output of the op amp toward the positive supply rail. I would remove it unless it unless there is a specific reason for it being there. If the intent is to shift the output value, this is best achieved by adding a voltage divider to the V+ input, rather than fighting with the op amp's output

My guess is that there is a mistaken connection and that R1 was intended to connect to the V- input instead of the positive supply rail.

I concur with others who have said to use a different op amp -- a &quot;rail to rail&quot; op amp. The output range of a 741 with a unipolar 5V supply is rather small.