Solid State Devices: Problems and Solutions - Electronic Properties of Materials | Deepak Rajput | drajput.com

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Electronic Properties of Materials: Solid State Devices - Problems and Solutions

Show that the change in the emitted wavelength with temperature T from an LED is approximately given by:

${{d{lambda}}/dT}{approx}-{hc}/{{E_g}^2}({{d{E}_g}/dT})$
where E_g is the bandgap. Consider a GaAs LED. The bandgap of GaAs at 300K is 1.42 eV, which changes (decreases) with temperature as dE_g/dT = -4.5 x 10^-4 ev K^-1. What is the change in the emitted wavelength if the temperature change is 10^oC?
A solar cell under an illumination of 1000 Wm^-2 has a short circuit current I_sc of 50 mA and an open circuit output voltage V_oc of 0.65 V. What are the short circuit current and open circuit voltages when the light intensity is halved?
Given the width of the relative light intensity between half-intensity points versus photon energy spectrum of an LED is typically ~3kT, what is the line width in the output spectrum in terms of the peak emission wavelength? Calculate the spectral linewidth of the output radiation from a green LED emitting at 570 nm at 300 K.