Mutual Energy Transfer in a Binary Colloidal Quantum Well Complex

Abstract

Forster resonance energy transfer (FRET) is a fundamental process that is key to optical biosensing, photosynthetic light harvesting, and downconverted light emission. However, in total, conventional FRET in a donor− acceptor pair is essentially unidirectional, which impedes practical application of FRET-based technologies. Here, we propose a mutual FRET scheme that is uniquely bidirectional in a binary colloidal quantum well (CQW) complex enabled by utilizing the d orbital electrons in a dopant−host CQW system. Steady-state emission intensity, time-resolved, and photoluminescence excitation spectroscopies have demonstrated that two distinct CQWs play the role of donor and acceptor simultaneously in this complex consisting of 3 monolayer (ML) copperdoped CQWs and 4 ML undoped CQWs. Band-edge excitons in 3 ML CQWs effectively transfer the excitation to excitons in 4 ML CQWs, whose energy is also harvested backward by the dopants in 3 ML CQWs. This binary CQW complex, which offers a unique mutual energy-transfer mechanism, may unlock revolutionary FRET-based technologies.

Modulating Emission Properties in a Host–Guest Colloidal Quantum Well Superlattice

“…Copper ions doped into CdSe CQWs can be realized by using both nucleation doping and partial cation exchange. [22,[27][28][29][30] However, the nucleation doping method generally results in rectangular-shaped CQWs which are difficult for long-range stacking. For this work, we prefer doped and undoped CQWs with similar dimensions to construct the binary superlattice, therefore, we follow our earlier report on partial cation exchange recipes, where we add a controllable amount of copper acetate precursor into a solution of square-shaped undoped four ML core CQWs.…”

“…modify the preference of exciton recombination channel via band-edge emission (BE) or copper emission (CE) due to an ultralong exciton hopping range (>100 nm) [17,20] and an ultrafast exciton hopping rate (≈4 ps). [11,17,22] By enlarging the vertical dimension of the binary superlattice, more photoexcited excitons are harvested by Cu dopants and as a result, the greenish and anisotropy photoluminescence (the intrinsic emission properties of BE) [12,13] is gradually changed into the reddish and isotropy photoluminescence (the intrinsic emission properties of CE). [22,23] In addition, we have modeled the excitonic dynamics (including exciton transfer, exciton trapping, and exciton recombination) in the binary superlattice, which can well-reproduce the controllability observed in the experiments.…”

“…[11,17,22] By enlarging the vertical dimension of the binary superlattice, more photoexcited excitons are harvested by Cu dopants and as a result, the greenish and anisotropy photoluminescence (the intrinsic emission properties of BE) [12,13] is gradually changed into the reddish and isotropy photoluminescence (the intrinsic emission properties of CE). [22,23] In addition, we have modeled the excitonic dynamics (including exciton transfer, exciton trapping, and exciton recombination) in the binary superlattice, which can well-reproduce the controllability observed in the experiments. This work, which expands the current understanding of manipulating collective properties in colloidal superlattices, could lead to novel photonic applications such as multimode optical anticounterfeiting, next-generation liquid crystal displays, and multifunctional biological markers.…”

Low‐Threshold Lasing from Copper‐Doped CdSe Colloidal Quantum Wells

“…From the perspective of fundamental understanding, the role of dopants in the bandgap modulation and steadystate/transient photoluminescence (PL) has been investigated into great depth. [5,[7][8][9][10][11] From the perspective of application, benefiting from the nearly zero self-absorption in the dopant related emission, Sharma et al demonstrated near-unity photoluminescence quantum yields in the luminescent solar concentrators using copper-doped colloidal quantum wells (CQWs). [4] To date, majority of the works on TMDCNMs are conducted with low pump fluence/intensity (i.e., stay in the sub-single/single exciton regime) and the potential of TMD-CNMs as optical gain materials has not aroused much attention.…”

“…From the perspective of fundamental understanding, the role of dopants in the bandgap modulation and steady‐state/transient photoluminescence (PL) has been investigated into great depth. [ 5,7–11 ] From the perspective of application, benefiting from the nearly zero self‐absorption in the dopant related emission, Sharma et al. demonstrated near‐unity photoluminescence quantum yields in the luminescent solar concentrators using copper‐doped colloidal quantum wells (CQWs).…”