Browsing by Author "Birowosuto, M. D."

Now showing 1 - 3 of 3

Open Access
Electrically control amplified spontaneous emission in colloidal quantum dots
(American Association for the Advancement of Science, 2019) Yu, J.; Shendre, S.; Koh, W.; Liu, B.; Li, M.; Hou, S.; Hettiarachchi, C.; Delikanlı, S.; Hernandez-Martinez, P.; Birowosuto, M. D.; Wang, H.; Sum, T.; Demir, Hilmi Volkan; Dang, C.
Colloidal quantum dots (CQDs) are highly promising materials for light amplification thanks to their efficient photoluminescence, tunable emission wavelength and low-cost synthesis. Unfortunately, CQDs are suffering from band-edge state degeneracy which demands multiple excitons to achieve population inversion. As a result, non-radiative Auger recombination increases the lasing threshold and limits the gain lifetime. Here, benefiting from the negative charging, we demonstrate that the amplified spontaneous emission (ASE) threshold is controllable in a device where CQD film is exposed to an external electric field. Specifically, singly charged CQDs lower the threshold due to the preexisting electron in the conduction band, while strongly enhanced Auger recombination in doubly charged CQDs stymies the ASE. Experimental results and kinetic equation model show that ASE threshold reduces 10% even if our device only charges ~17% of the CQD population. Our results open new possibilities for controlling exciton recombination dynamics and achieving electrically pumped CQD lasers.
Open Access
Mutual energy transfer in a binary colloidal quantum well complex
(American Chemical Society, 2019) Yu, J.; Sharma, Manoj; Delikanlı, Savaş; Birowosuto, M. D.; Demir, Hilmi Volkan; Dang, C.
Förster resonance energy transfer (FRET) is a fundamental process that is key to optical biosensing, photosynthetic light harvesting, and down-converted 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) copper-doped 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.
Open Access
Strong plasmon-wannier mott exciton interaction with high aspect ratio colloidal quantum wells
(Cell Press, 2020) Yu, J.; Hou, S.; Sharma, Manoj; Tobing, L. Y. M.; Song, Z.; Delikanlı, Savaş; Hettiarachchi, C.; Zhang, D.; Fan, W.; Birowosuto, M. D.; Wang, H.; Demir, Hilmi Volkan; Dang, C.
The strong interaction between excitons and plasmons, manifested as Rabi splitting of the eigen energies, is of fundamental interest for manipulating photons in nanoscale devices. Thanks to their enhanced photostability and minimal inhomogeneous broadening compared with organic molecules, inorganic emitters are preferred for practical applications. However, a relatively small Rabi splitting with inorganic materials severely hinders the active plasmonic operation, considering its weak optical nonlinearity and slow energy interexchange. Here, we circumvent this problem in a hybrid system consisting of high aspect ratio colloidal quantum wells (HARCQWs) and an individual plasmonic silver nanocube. By taking advantages of a highly in-plane oriented exciton, enhanced exciton binding energy, and non-stacking properties in HARCQWs, we demonstrate an unprecedented giant Rabi splitting energy up to 400 meV under ambient conditions, which is observed not only in scattering but also in photoluminescent spectra. These findings are a key step toward achieving inorganic plasmonic devices.