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The engineering of efficient photodetectors with a nonlinear response to light is an important task for modern optoelectronics because this allows the fabrication of fully light-controlled devices. The two-photon absorption (TPA) phenomenon allows 3D confinement of the excitation and thus, hence, the fabrication of 3D arrays of light-sensitive elements. Moreover, this type of excitation ensures the control of the response efficiency by tuning the intensity of the light. Current technologies mainly use photodiodes based on bulk semiconductors, but the use of colloidal semiconductor quantum dots (QDs) has more advantages due to ease of processing, precisely-controlled optoelectronic properties, quick response, and compatibility with flexible substrates. Moreover, QDs have very high two-photon absorption cross-sections in a wide spectral range in the infrared region. Nevertheless, to activate such photodetectors in the nonlinear optical mode, peak excitation intensities higher than GW/cm^2 are still required. To reduce the excitation intensity it is needed to further increase the TPA. To achieve it we designed plasmon–exciton hybrid material using plasmon nanoparticles (PNPs) with an absorption peak overlapped with excitation wavelength. We found that the effective TPA in QDs near PNPs increased by the order of magnitude due to the nonlinear energy transfer from plasmons in PNPs to excitons of QDs. Finally, we designed a near-infrared plasmon–exciton photodetector based on the designed plasmon-exciton hybrid material. We investigated the effect of plasmons on the photoresponse of the photodetector under near-infrared two-photon excitation of QDs. As a result, we have found that the photocurrent was up to 38 times higher in the detector filled with QD–PNP plasmon–exciton hybrid material than in the detector filled with QDs alone.
This study was supported by the Russian Science Foundation, grant no. 18-72-10143-П. V.K. has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie, grant agreement no. 101025664 (QESPEM).
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