Ultrafast transient absorption study of hot carrier dynamics in hafnium nitride and zirconium nitride

Xiaoming Wen, Simon Chung, Neeti Gupta, Hongze Xia, Yu Feng, Santosh Shrestha, Shujuan Huang, Tak W. Kee, Takaaki Harad, Gavin Conibeer

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contributionpeer-review


Hot carrier solar cell (HCSC) is a promising third generation photovoltaic device which can potentially able to overcome the Shockley-Queisser limit and achieve much higher power efficiency than present single junction solar cells. The theoretical efficiency for an ideal HCSC is predicted to be 65% under 1 sun solar radiation or 85% under maximal concentration. A critical requirement of the absorber is to slow down the cooling rate of photoexcited hot carriers, from few ps for typical semiconductors to hundreds of ps or longer. Transition nitrides HfN and ZrN theoretically have large phononic bandgaps and thus much slowed cooling time may be expected in these materials. In this investigation ultrafast transient absorption (TA) was used to investigate HfN and ZrN thin films. Experiments reveal three featured TA bands in the visible and near infrared, ascribed to the excited state absorption and bleaching. Cooling time of hot carriers as long as 3 ns in HfN is attributed to the significantly suppressed Klemens' decay. While hundreds of ps cooling time were observed in ZrN. The slowed thermalization process in HfN and ZrN suggests these bulk materials are a promising absorber candidate for hot carrier solar cells.

Original languageEnglish
Title of host publication2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC)
Place of PublicationPiscataway, NJ
PublisherInstitute of Electrical and Electronics Engineers (IEEE)
Number of pages4
ISBN (Electronic)9781479979448, 9781479979431
Publication statusPublished - 2015
Externally publishedYes
Event42nd IEEE Photovoltaic Specialist Conference, PVSC 2015 - New Orleans, United States
Duration: 14 Jun 201519 Jun 2015


Conference42nd IEEE Photovoltaic Specialist Conference, PVSC 2015
Country/TerritoryUnited States
CityNew Orleans


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