Charge Transfer from Lead Sulfide Quantum Dots to MoS 2 Nanoplatelets
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ANOPHOTONICS
Charge Transfer from Lead Sulfide Quantum Dots to MoS2 Nanoplatelets1 I. D. Skurlova, *, A. S. Mudraka, A. V. Sokolovaa, S. A. Cherevkova, M. A. Baranova, A. Dubavika, P. S. Parfenova, and A. P. Litvina a ITMO
University, St. Petersburg, 197101 Russia *e-mail: [email protected]
Received January 18, 2020; revised January 18, 2020; accepted April 20, 2020
Abstract—The research interest in the transition metal dichalcogenides (TMD) has been reborn a few years ago. This had happened due to the remarkable properties of monolayered TMD (e.g., high carrier mobility and high exciton binding energy) and due to the development of the exfoliation methods. Photoconductive MoS2-based devices spectral range can be expanded to the NIR by coupling them with PbS QDs. However, this requires extensive knowledge about the charge and energy transfer processes in such systems. In this paper, we investigate charge transfer between PbS QDs and MoS2 nanoplatelets (NPls). Using the PL decay analysis, we show how the charge transfer efficiency changes with the distance between the QDs and NPls, as well as with QD size. Last, we demonstrate that the addition of the MoS2 NPLs increases the photoconductive response for up to an order of magnitude, as compared to the bare QD. Keywords: transition metal dichalcogenides, quantum dots, charge transfer, lead sulfide, molybdenum disulfide DOI: 10.1134/S0030400X20080330
INTRODUCTION Transition metal dichalcogenides (TMD, e.g., MoS2, MoSe2, WS2) have attracted much attention for the last years [1–3]. Bulk TMD have layered structure where each layer bounds to another one with weak van der Waals interactions. These layers can be separated from each other by means of various exfoliation methods [4]. When TMD thickness approaches one monolayer, its indirect bandgap becomes a direct one. It happens due to quantum confinement as well as the hybridization change in the TMD [5]. Comparing to the bulk, monolayer TMD demonstrate increase in photoluminescence (PL) quantum yield at least up to a factor of 10 4 [6]. Another advantage of TMD is their exceptional carrier mobility, which can be exploited to create efficient field-effect transistors and photodetectors [7]. However, widely studied TMD predominantly have high bandgap values, hence they cannot absorb NIR light. Quantum dots (QD) are 0D semiconductor nanoparticles with size-dependent properties due to the quantum confinement effect. Some of the QDs have extensive absorption throughout NIR range (e.g., PbS, PbSe and HgTe) [8]. Lead sulfide QDs have been employed as an active layer of newgeneration photovoltaic cells [9] and NIR light detec1 The 2nd International School-Conference for young researchers
“Smart Nanosystems for Life,” St. Petersburg, Russia, December 10–13, 2019.
tors [10]. By combining the TMD and QDs it is possible to expand the spectral range of the photodetectors and improve their responsivity. Prototype devices, based on the combination of TMD and PbS QDs have already been reported in recent years [11–13]. Performance of suc
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