Non-Resonant Below-Bandgap Two-Photon Absorption in Quantum Dot Solar Cells

摘要

We are the first to show with clear experimental results that photons thathave energy lower than the transition energy between quantum dots states andvalance band can still contribute greatly to the photocurrent via bothone-photon absorption process (1PA) and two-photon absorption process (2PA).The tailing states function as both the energy states for low energy photonabsorption and the photocarriers extraction pathway. One of the biggestadvantages of our method is that it can clearly differentiate the photocurrentdue to 1PA process and 2PA process. Both 1PA and 2PA photocurrent generationefficiency in an InAs/GaAs QD device with photon excitation at 1550 nm havebeen quantitatively evaluated.