The photocurrent in a photodiode depends on

State the band gap of the semiconductor used in the making of $LED$.

Consider a situation in which reverse biased current of a particular $P-N$ junction increases when it is exposed to light of wavelength $\lambda \le 621 \, nm$. During this process,enhancement in carrier concentration takes place due to the generation of hole-electron pairs. The value of the band gap is nearly (in $eV$):

The material suitable for making a solar cell is

What kind of $p-n$ junction diode does not require any kind of bias?

What are optoelectronic devices? Give the names of such major devices.