Calculate room temperature theoretical efficiency of a solar cell made from a semiconductor with the energy gap E_G=1.8 eV, N_C=N_V=1 10¹⁹ cm^-3, and N_A=N_D=10¹⁷ cm^-3. The device series resistance is 1 . Assume 5% reflection and no photon absorption for photons with the energy below the energy gap. Also, assume that light with wavelength 250 nm will be absorbed by the device surface and the electron-hole pairs will not contribute to photocurrent due to surface recombination. Use 90% quantum efficiency of electron-hole photogeneration. (b) Assume that the Sun's temperature has decreased to T=4500K and the Earth's average surface temperature is -25^o Calculate the electrical power produced by the same solar cell (see part 2a) with an area of A=2.5 m².