Observation of biexcitons in the presence of trions generated via sequential absorption of multiple photons in colloidal quantum dot solids

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buir.contributor.orcidDemir, Hilmi Volkan|0000-0003-1793-112X
dc.citation.epage757en_US
dc.citation.spage756en_US
dc.contributor.authorCihan, Ahmet Fatihen_US
dc.contributor.authorHernandez-Martinez Pedro L.en_US
dc.contributor.authorKelestemur, Yusufen_US
dc.contributor.authorDemir, Hilmi Volkanen_US
dc.coverage.spatialBurlingame, CA, USAen_US
dc.date.accessioned2016-02-08T12:11:45Z
dc.date.available2016-02-08T12:11:45Z
dc.date.issued2012en_US
dc.departmentDepartment of Electrical and Electronics Engineeringen_US
dc.departmentDepartment of Physicsen_US
dc.departmentInstitute of Materials Science and Nanotechnology (UNAM)en_US
dc.descriptionDate of Conference: 23-27 September 2012en_US
dc.description.abstractMulti exciton generation (MEG) and multi exciton recombination (MER) in semiconductor quantum dots (QDs) have recently attracted significant scientific interest as a possible means to improve device efficiencies [1-5]. Convenient bandgap tunability, easy colloidal synthesis, and solution-based processability of these QDs make them further attractive for such device applications using MEG and MER. For example, recent theoretical and experimental studies have shown that MEG enables >100% peak external quantum efficiency where the generated multi excitons (MEs) are collected in a simple QD solar cell structure [1]. Furthermore, MEG has also been shown in QD photodetectors exhibiting substantially increased photocurrent levels [2]. Another promising application for MEs is the use of QDs as an alternative gain medium based on MER for lasers. Although MEG is very promising and supported with quite persuasive reports, there are still some debatable issues that need to be clarified. One of the issues that have generated great debates in the field has been the confusion of MER with the recombination of trions, which takes place in photocharged QDs. To utilize MEG and MER in practical devices such as QD solar cells and QD lasing devices, these phenomena need to be well understood. Here, we showed distinct spectrally-resolved temporal behavior of biexciton (BX), single exciton (X) and trion radiative recombinations in near unity quantum yield (QY) quasi-type II CdSe/CdS core/shell nanocrystal QDs. Upon sequential absorption of multiple photons, the extraction of Xs, BXs, and trions were achieved using time correlated single photon counting (TCSPC) measurements performed on low concentration thin film samples of these QDs at different emission wavelengths. The QDs were embedded in PMMA medium to obtain homogeneous samples and avoid Förster-type nonradiative energy transfer (NRET) between them. Here to extract Xs, BXs, and trions, we devised a new analysis approach for the time decays of the QDs that allowed us to attribute the physical events to their corresponding time decay terms, which were further verified with their excitation intensity dependencies [6]. © 2012 IEEE.en_US
dc.identifier.doi10.1109/IPCon.2012.6358843en_US
dc.identifier.urihttp://hdl.handle.net/11693/28122
dc.language.isoEnglishen_US
dc.publisherIEEEen_US
dc.relation.isversionofhttp://dx.doi.org/10.1109/IPCon.2012.6358843en_US
dc.source.titleIEEE Photonics Conference 2012en_US
dc.subjectAnalysis approachen_US
dc.subjectBiexcitonsen_US
dc.subjectCdSe/CdSen_US
dc.subjectColloidal synthesisen_US
dc.subjectCore/shell nanocrystalsen_US
dc.subjectDevice applicationen_US
dc.subjectDevice efficiencyen_US
dc.subjectEmission wavelengthen_US
dc.subjectExcitation intensityen_US
dc.subjectExperimental studiesen_US
dc.subjectExternal quantum efficiencyen_US
dc.subjectGain mediumen_US
dc.subjectHomogeneous samplesen_US
dc.subjectLow concentrationsen_US
dc.subjectMultiexcitonsen_US
dc.subjectNonradiative energy transferen_US
dc.subjectProcessabilityen_US
dc.subjectQuantum dot solidsen_US
dc.subjectRadiative recombinationen_US
dc.subjectSingle excitonsen_US
dc.subjectSolar cell structuresen_US
dc.subjectTemporal behavioren_US
dc.subjectTime decayen_US
dc.subjectTime-correlated single-photon countingen_US
dc.subjectTunabilitiesen_US
dc.subjectEnergy transferen_US
dc.subjectExcitonsen_US
dc.subjectPhotonsen_US
dc.subjectQuantum yielden_US
dc.subjectSemiconductor quantum dotsen_US
dc.subjectSolar cellsen_US
dc.subjectPhotonicsen_US
dc.titleObservation of biexcitons in the presence of trions generated via sequential absorption of multiple photons in colloidal quantum dot solidsen_US
dc.typeConference Paperen_US
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Department of Electrical and Electronics Engineering
Department of Physics
Institute of Materials Science and Nanotechnology (UNAM)