Carrier dynamics and phonon properties of hafnium nitride: Potential hot carrier solar cell absorber

Hot carrier solar cells aims to circumvent fundamental loss mechanisms by extracting carriers before thermalization of hot carriers occurs while also minimizing sub-bandgap losses. The absorber must be able to maintain a hot carrier for a sufficiently long time. Hafnium nitride owing to its phononic properties to slow carrier thermalization is a potential absorber for the hot carrier solar cell. The phonon properties have been measured by Raman spectroscopy. The carrier dynamics in hafnium nitride has been studied by ultrafast pump-probe transient absorption where nanosecond long lifetimes have been observed. The carrier temperature has been extracted from the transient absorption spectra to show the carrier temperature remained above 350 K for a long time with a decay time constant of 1.2 ns.