Explore the Intervalley Scattering on Phonon Bottleneck Effect and Its Application on Hot Carrier Solar Cells

Hot carrier solar cells with theoretical efficiency upon to 66% in one sun condition by utilizing thermalization energy have been intensively studied in recent years. However, practical device of this cell has not yet been realized. Because it is difficult to utilize highly energetic carriers before thermalization. One approach to overcome this is effectively reducing thermalization rate via phonon bottleneck effect. A slowed carrier intervalley scattering will also enhance this effect via Frohlich interaction. Herein, the relationship between intervalley scattering and phonon bottleneck effect in Al x Ga (1-x) As/AlAs heterojunctions was studied. It shows that the carrier thermalization rate was significantly reduced once the carriers could access the satellite valleys. Moreover, the carrier lifetime extends with increasing GaAs molar fraction when intervalley scattering occurs. Because GaAs could effectively store the carriers in the satellite valleys due to much smaller Frohlich constant, which enhances the phonon bottleneck effect and reduces carrier cooling rate.