Optoelectronics: Photodiodes, LEDs, and Solar Cells
1. What is the primary function of a solar cell?
2. In an LED, which parameter directly determines the color of the emitted light?
3. Which device operates in reverse bias and generates current due to incident photons?
4. A photodiode has Popt = 1.5 mW, η = 0.8, and hν = 2.5 × 10⁻¹⁹ J. Calculate Iph. Use q = 1.6 × 10⁻¹⁹ C.
5. In an LED, if Rnonrad >> Rrad, what happens to the external quantum efficiency?
6. A solar cell delivers Voc = 0.55 V, Isc = 25 mA, FF = 0.78, and Pin = 60 mW. Calculate its efficiency.
7. A GaAs LED emits photons of λ = 850 nm. What is the approximate photon energy?
8. A solar cell has Voc = 0.7 V, Isc = 40 mA, and FF = 0.72. If the input power is 120 mW, find the efficiency η.
9. In a laser diode, threshold current Ith increases primarily due to: