Abstract:Infrared photodetection based on colloidal nanoparticles is a promising path toward low cost devices. However, mid-infrared absorption relies on interband transitions in heavy metal-based materials, which is a major flaw for the development toward mass market. In the quest of mercury-free 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 … Show more
“…These performances are weak compared with the one reported for HgTe nanocrystals with interband transition at the same wavelength, in which case responsivity in the 1 to 100 mA/W is currently achieved 2,4 . This is, on the other hand, similar to other Hg-free material such as Ag2Se 19 nanocrystals, which present intraband absorption around 5 µm and for which responsivity reaches 8 µA/W.…”
Section: Figure 4 a Scheme Of A Non-functionalized Nanoparticle Whersupporting
Nanocrystals are often described as interesting materials for the design of low-cost optoelectronic devices especially in the infrared range. However the driving materials reaching infrared absorption are generally heavy metalcontaining (Pb and Hg) with a high toxicity. An alternative strategy to achieve infrared transition is the use of doped semiconductors presenting intraband or plasmonic transition in the short, mid and long-wave infrared. This strategy may offer more flexibility regarding the range of possible candidate materials. In particular, significant progress have been achieved for the synthesis of doped oxides and for the control of their doping magnitude. Among them, tin doped indium oxide (ITO) is the one providing the broadest spectral tunability. Here we test the potential of such ITO nanoparticles for photoconduction in the infrared. We demonstrate that In2O3 nanoparticles present an intraband absorption in the mid infrared range which is transformed into a plasmonic feature as doping is introduced. We have determined the cross section associated with the plasmonic transition to be in the 1-3x10-13 cm 2 range. We have observed that the nanocrystals can be made conductive and photoconductive due to a ligand exchange using a short carboxylic acid, leading to a dark conduction with n-type character. We bring evidence that the observed photoresponse in the infrared is the result of a bolometric effect.
“…These performances are weak compared with the one reported for HgTe nanocrystals with interband transition at the same wavelength, in which case responsivity in the 1 to 100 mA/W is currently achieved 2,4 . This is, on the other hand, similar to other Hg-free material such as Ag2Se 19 nanocrystals, which present intraband absorption around 5 µm and for which responsivity reaches 8 µA/W.…”
Section: Figure 4 a Scheme Of A Non-functionalized Nanoparticle Whersupporting
Nanocrystals are often described as interesting materials for the design of low-cost optoelectronic devices especially in the infrared range. However the driving materials reaching infrared absorption are generally heavy metalcontaining (Pb and Hg) with a high toxicity. An alternative strategy to achieve infrared transition is the use of doped semiconductors presenting intraband or plasmonic transition in the short, mid and long-wave infrared. This strategy may offer more flexibility regarding the range of possible candidate materials. In particular, significant progress have been achieved for the synthesis of doped oxides and for the control of their doping magnitude. Among them, tin doped indium oxide (ITO) is the one providing the broadest spectral tunability. Here we test the potential of such ITO nanoparticles for photoconduction in the infrared. We demonstrate that In2O3 nanoparticles present an intraband absorption in the mid infrared range which is transformed into a plasmonic feature as doping is introduced. We have determined the cross section associated with the plasmonic transition to be in the 1-3x10-13 cm 2 range. We have observed that the nanocrystals can be made conductive and photoconductive due to a ligand exchange using a short carboxylic acid, leading to a dark conduction with n-type character. We bring evidence that the observed photoresponse in the infrared is the result of a bolometric effect.
“…This strategy is nevertheless currently limited to the MWIR and LWIR and the level of performance is by far not as good as their interband counterparts. Ag 2 Se, thanks to its spectral vicinity with HgSe has recently generated some interest for MWIR detection (Sahu et al, 2012 ; Park et al, 2018 ; Qu et al, 2018 ), although detection performances remain for now several orders of magnitude below than what have been reported with HgX compounds.…”
Infrared (IR) sensors based on epitaxially grown semiconductors face two main challenges which are their prohibitive cost and the difficulty to rise the operating temperature. The quest for alternative technologies which will tackle these two difficulties requires the development of new IR active materials. Over the past decade, significant progresses have been achieved. In this perspective, we summarize the current state of the art relative to nanocrystal based IR sensing and stress the main materials, devices and industrial challenges which will have to be addressed over the 5 next years.
“…Further studies (Qu et al and Park et al) using Ag 2 Se CQDs based on this synthesis were employed to investigate the origin of the MWIR absorption and the photoconductivity of Ag 2 Se CQD devices [58, 59]. Qu et al updated the synthesis slightly to prevent aggregation of the Ag 2 Se CQDs by also quenching the reaction with DDT ligands to stabilize the particles.…”
Section: Colloidal Synthesis and Characterization Of Thermal Infraredmentioning
confidence: 99%
“…The Ag 2 Se CQD film ligand-exchanged with standard ethanedithiol ligands exhibited limited responsivity, on the order of few μA/W, which is orders of magnitude lower that of the HgSe CQDs (Fig. 24b) [59]. Combined materials and device characterization research efforts are further warranted to examine the full potential of this new colloidal nanomaterial.Fig.…”
Section: Thermal Infrared Colloidal Quantum Dots Based Devicesmentioning
Colloidal quantum dots provide a powerful materials platform to engineer optoelectronics devices, opening up new opportunities in the thermal infrared spectral regions where no other solution-processed material options exist. This mini-review collates recent research reports that push the technological envelope of colloidal quantum dot-based photodetectors toward mid- and long-wavelength infrared. We survey the synthesis and characterization of various thermal infrared colloidal quantum dots reported to date, discuss the basic theory of device operation, review the fabrication and measurement of photodetectors, and conclude with the future prospect of this emerging technology.
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