Energy-transfer pumping of semiconductor nanocrystals using an epitaxial quantum well

Abstract

As a result of quantum-confinement effects, the emission colour of semiconductor nanocrystals can be modified dramatically by simply changing their size. Such spectral tunability, together with large photoluminescence quantum yields and high photostability, make nanocrystals attractive for use in a variety of light-emitting technologies--for example, displays, fluorescence tagging, solid-state lighting and lasers. An important limitation for such applications, however, is the difficulty of achieving electrical pumping, largely due to the presence of an insulating organic capping layer on the nanocrystals. Here, we describe an approach for indirect injection of electron-hole pairs (the electron-hole radiative recombination gives rise to light emission) into nanocrystals by non-contact, non-radiative energy transfer from a proximal quantum well that can in principle be pumped either electrically or optically. Our theoretical and experimental results indicate that this transfer is fast enough to compete with electron-hole recombination in the quantum well, and results in greater than 50 per cent energy-transfer efficiencies in the tested structures. Furthermore, the measured energy-transfer rates are sufficiently large to provide pumping in the stimulated emission regime, indicating the feasibility of nanocrystal-based optical amplifiers and lasers based on this approach.

Outermost tensile strain dominated exciton emission in bending CdSe nanowires

“…CdSe nanowires based functional devices, such as transistors, photovoltaic cells [1], light-emitting diodes [2], lasers [3], etc., have been developed. Further modulation of the electronic structures and control of the transport dynamics of carriers in CdSe nanostructures are very important to optimize the optoelectronic properties.…”

Photophysical studies of CdTe quantum dots in the presence of a zinc cationic porphyrin

“…17 However, only a handful of studies have probed the charge and energy dynamics of CdTe QDs on the ultrafast timescale and even fewer have 40 considered how these dynamics are influenced by the presence of suitable electron donor or acceptor surface species. [18][19][20][21][22][23][24][25][26] Due to the role in natural photosynthesis of related compounds porphyrin molecules have been extensively exploited for electron and energy transfer. [27][28][29][30] The light-harvesting properties of porphyrins 45 has led them to be considered as components in solar photovoltaic cells.…”

Nonradiative exciton energy transfer in hybrid organic-inorganic heterostructures

“…Time-resolved studies in hybrid quantum well heterostructures have demonstrated the effect of an extra decay channel in the quantum well emission (donor) [12][13][14]. However, this alone cannot be taken as evidence of energy transfer to the acceptor sites because the deposition of an overlayer of organic dye molecules, fluorophores or colloidal quantum dots on the quantum well barrier separating donor and acceptor sites could lead to modification of its surface states, which would itself modify the decay dynamics.…”

“…First experimental evidence of the above mechanism was observed in hybrid structures between Wannier excitons in wide band gap semiconductor quantum wells (donors) and colloidal semiconductor quantum dots [12,13] (acceptors) or Frenkel excitons in organic fluorophores [14][15][16].…”