Very, very low. I won't go into too much detail here, but LEDs and solar PN junctions (aka diodes) have very different designs.
The two big things I will mention are that LEDs are made with direct band gap semiconductors whereas efficient solar cells are made with indirect bandgap semiconductors.
The other issue is that solar cells rely on as big of a depletion region as possible to collect light whereas in LEDs the depletion region is considerably smaller.
The two big things I will mention are that LEDs are made with direct band gap semiconductors whereas efficient solar cells are made with indirect bandgap semiconductors.
The other issue is that solar cells rely on as big of a depletion region as possible to collect light whereas in LEDs the depletion region is considerably smaller.