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<p>The energy transfer mechanism between a nickel oxide (NiO) hole transport layer and core/shell CdSe/ZnS quantum dots (QDs) is examined and applied in all-inorganic quantum dot light emitting devices. The hole transport into the QDs in these devices has been reported to be possible by hole injection through the transport layer. An alternate mechanism, in the form of resonance energy transfer, is explored by investigating the carrier dynamics in QD/NiO bilayers using time-resolved photoluminescence spectroscopy as a function of QD size. The NiO thin film is processed such that it is non-stoichiometric with trap states around the QD bandgap energy. The QD fluorescence lifetime in the bilayer is longer than that on bare glass and shows a strong dependence on the size of the QDs, which can be attributed to delayed emission resulting from energy transfer from the NiO to the QD. To verify that the energy transfer occurs in real all-inorganic QLED devices, a yellow QLED operating at 589 nm and a red QLED operating at 645 nm are fabricated using a NiO hole transport layer and a ZnO electron transport layer. The red QLED exhibits superior energy transfer efficiency due to greater spectral overlap, achieving approximately four times the performance of the yellow QLED. It reaches a peak external quantum efficiency of 6.04% and a current efficiency of 4.36 cd/A.</p>

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All-inorganic QLEDs utilizing resonant energy transfer between non-stoichiometric nickel oxide hole transport layer and alloyed CdSe/ZnS quantum dots

  • 期刊论文

  • 发表日期：

    2025年7月7日

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  • Ramesh Vasan,
  • Feng Gao,
  • M. Omar Manasreh,
  • Colin D. Heyes

摘要

The energy transfer mechanism between a nickel oxide (NiO) hole transport layer and core/shell CdSe/ZnS quantum dots (QDs) is examined and applied in all-inorganic quantum dot light emitting devices. The hole transport into the QDs in these devices has been reported to be possible by hole injection through the transport layer. An alternate mechanism, in the form of resonance energy transfer, is explored by investigating the carrier dynamics in QD/NiO bilayers using time-resolved photoluminescence spectroscopy as a function of QD size. The NiO thin film is processed such that it is non-stoichiometric with trap states around the QD bandgap energy. The QD fluorescence lifetime in the bilayer is longer than that on bare glass and shows a strong dependence on the size of the QDs, which can be attributed to delayed emission resulting from energy transfer from the NiO to the QD. To verify that the energy transfer occurs in real all-inorganic QLED devices, a yellow QLED operating at 589 nm and a red QLED operating at 645 nm are fabricated using a NiO hole transport layer and a ZnO electron transport layer. The red QLED exhibits superior energy transfer efficiency due to greater spectral overlap, achieving approximately four times the performance of the yellow QLED. It reaches a peak external quantum efficiency of 6.04% and a current efficiency of 4.36 cd/A.