Nanoscale physics

Size-Dispersed ZnSe Quantum Dots as Artificial Antennas: Role of Quasi-Coherent Regime of Excitons for Enhanced Light Harvesting and Energy Transfer
Bondar N.V.1a, M.S. Brodyn1.
1Departament of nonlinear optics, Institute of Physics of NASU, Ukraine.
      Prospect Nauki, 46, Kyiv-03028, Ukraine. 
        1a E-mail: nanodot50@gmail.com

A most challenging and active area of research nowadays are studies of the sources renewable energy and the processes of the harvesting, build-up and transfer of excitation energy to organic and inorganic semiconductor structures and to construct the photosynthetic structure for photovoltaic. In this work we extend our previous findings [1] and by analyzing absorption, photoluminescence excitation and photoluminescence emission spectra, and also their emission lifetimes demonstrate that in dense packed energy-gradient films of ZnSe QDs, as a connected QDs-network, an excitonic energy transfer (EET) to QDs-acceptors resembles real the processes in a light-harvesting antenna system of photosynthetic structures. We found that an unexpected gain of EET in films excited by weak incoherent radiation can be explained by resonantly transferred through both the quantum states and so-called an intrinsic gap states of QDs [2], but not through the surface (trapped) states of excitons, as stated before. We found that an efficiency of EET considerable increases with decreasing of the photon energy result from the delocalization of an exciton wavefunctions and the formation of quasi-coherent regime of EET. In addition, comparison our findings and other authors indicated that the PL emission of QDs on basis of Zn (or Cd) -chalcogenide with radii  2 nm consisted of surface bands lying below of the gap of the bulk ZnSe and most probably arises from the intrinsic defects of ZnSe QDs.

1.	N.V. Bondar, M.S. Brodyn, N.A. Matveevskaya, T.G. Beynik.
Efficient and Sub-Nanosecond Resonance Energy Transfer in Close-Packed Films of ZnSe Quantum Dots by Steady-State and Time-Resolved Spectroscopy // Supperlatt. and Microctr.. – 2020. – 138. – P. 106382.