Intraband Mid-Infrared Transitions in Ag 2 Se Nanocrystals: Potential and Limitations for Hgfree Low Cost Photodetection
Résumé
Infrared photodetection based on colloidal nanoparticles is a promising path toward low cost devices. However, mid-infrared absorption relies on interband transition in heavy metal based materials, which is a major flaw for the development toward mass market. In the quest of infrared active colloidal materials, we here investigate Ag2Se nanoparticles presenting intraband transition between 3 and 15 µm. With photoemission and infrared spectroscopy, we are able to propose an electronic spectrum of the material in absolute energy scale. We also investigate the origin of doping and demonstrate that it is the result of cation excess under Ag+ form. We demonstrate photoconduction into this material including under resonant excitation of the intraband transition. However, performances are currently quite weak with (i) a slow photoresponse (several seconds), and (ii) some electrochemical instabilities at room temperature.
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