Spectrally Resolved Interband and Intraband Transitions by Two-Step Photon Absorption in InGaAs/GaAs Quantum Dot Solar Cells

Two-step photon absorption processes in a self-organized In
_0.4
Ga
_0.6
As/GaAs quantum dot solar cell have been investigated by means of infrared (IR) light-biased change in external quantum efficiency (ΔEQE) spectroscopy at 9 K. In this paper, not only interband transitions but intraband transitions were both spectrally resolved by utilizing wavelength tunable intense mid-IR pulsed laser as the IR bias light source. The obtained EQE enhancement was attributed from reexcitation of photocarriers captured by quantum dots. The bound-to-continuum intraband transition probability was estimated to be about 8% by irradiating 100-suns-equivalent IR bias light.