scholarly journals Spin blockade and phonon bottleneck for hot electron relaxation observed in n-doped colloidal quantum dots

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Junhui Wang ◽  
Lifeng Wang ◽  
Shuwen Yu ◽  
Tao Ding ◽  
Dongmei Xiang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Phonon Scattering ◽  
Surface States ◽  
Hot Electrons ◽  
Hot Electron ◽  
Phonon Bottleneck ◽  
Spin Interactions ◽  
Doped Quantum Dots ◽  
Electron Relaxation ◽  
Spin Blockade

AbstractUnderstanding and manipulating hot electron dynamics in semiconductors may enable disruptive energy conversion schemes. Hot electrons in bulk semiconductors usually relax via electron-phonon scattering on a sub-picosecond timescale. Quantum-confined semiconductors such as quantum dots offer a unique platform to prolong hot electron lifetime through their size-tunable electronic structures. Here, we study hot electron relaxation in electron-doped (n-doped) colloidal CdSe quantum dots. For lightly-doped dots we observe a slow 1Pe hot electron relaxation (~10 picosecond) resulting from a Pauli spin blockade of the preoccupying 1Se electron. For heavily-doped dots, a large number of electrons residing in the surface states introduce picosecond Auger recombination which annihilates the valance band hole, allowing us to observe 300-picosecond-long hot electrons as a manifestation of a phonon bottleneck effect. This brings the hot electron energy loss rate to a level of sub-meV per picosecond from a usual level of 1 eV per picosecond. These results offer exciting opportunities of hot electron harvesting by exploiting carrier-carrier, carrier-phonon and spin-spin interactions in doped quantum dots.

scholarly journals Observation of a phonon bottleneck in copper-doped colloidal quantum dots

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Lifeng Wang ◽  
Zongwei Chen ◽  
Guijie Liang ◽  
Yulu Li ◽  
Runchen Lai ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Cadmium Selenide ◽  
Phonon Scattering ◽  
Photochemical Reactions ◽  
Hot Electrons ◽  
Colloidal Quantum Dots ◽  
Hot Electron ◽  
Electron Cooling ◽  
Phonon Bottleneck ◽  
Cooling Mechanism

Abstract Hot electrons can dramatically improve the efficiency of solar cells and sensitize energetically-demanding photochemical reactions. Efficient hot electron devices have been hindered by sub-picosecond intraband cooling of hot electrons in typical semiconductors via electron-phonon scattering. Semiconductor quantum dots were predicted to exhibit a “phonon bottleneck” for hot electron relaxation as their quantum-confined electrons would couple very inefficiently to phonons. However, typical cadmium selenide dots still exhibit sub-picosecond hot electron cooling, bypassing the phonon bottleneck possibly via an Auger-like process whereby the excessive energy of the hot electron is transferred to the hole. Here we demonstrate this cooling mechanism can be suppressed in copper-doped cadmium selenide colloidal quantum dots due to femtosecond hole capturing by copper-dopants. As a result, we observe a lifetime of ~8.6 picosecond for 1Pe hot electrons which is more than 30-fold longer than that in same-sized, undoped dots (~0.25 picosecond).

Photons and charges from colloidal doped semiconductor quantum dots

2019 ◽  
Vol 7 (47) ◽  
pp. 14788-14797 ◽  
Author(s):  
Tian Qiao ◽  
David Parobek ◽  
Dong Hee Son
Keyword(s):  
Quantum Dots ◽  
Semiconductor Quantum Dots ◽  
Hot Electrons ◽  
Doped Quantum Dots

This work discusses the photophysical pathways in doped quantum dots responsible for generating photons of non-exciton origin and hot electrons.

Hot Electron Relaxation in Quantum Wells

1986 ◽  
Vol 77 ◽  
Author(s):  
S. A. Lyon
Keyword(s):  
Crystal Growth ◽  
Steady State ◽  
Quantum Wells ◽  
Hot Electrons ◽  
Two Dimensional ◽  
Hot Electron ◽  
Carrier Distribution ◽  
Bulk Gaas ◽  
Bulk Semiconductors ◽  
Electron Relaxation

ABSTRACTHot electron relaxation in bulk semiconductors has been studied for several decades, but only through recent advances in crystal growth has it become possible to investigate the ther-malization of hot quasi-two-dimensional carriers in quantum wells. These same advances have opened the possibility of constructing various semiconductor devices which rely on hot electrons for their operation. We discuss experimental results on the energy relaxation of hot electrons in GaAs/AlGaAs quantum wells. The experiments make use of optical spectroscopy for determining the carrier distribution. In particular, steady-state hot photoluminescence measurements have been employed with modulation-doped quantum wells in order to minimally perturb the system by the photoexcited carriers. Both the relaxation of very energetic electrons and the cooling of a hot thermalized carrier distribution are considered. The quantum well results are compared to results from similar experiments with bulk GaAs.

scholarly journals Ab initio study of hot electrons in GaAs

2015 ◽  
Vol 112 (17) ◽  
pp. 5291-5296 ◽  
Author(s):  
Marco Bernardi ◽  
Derek Vigil-Fowler ◽  
Chin Shen Ong ◽  
Jeffrey B. Neaton ◽  
Steven G. Louie
Keyword(s):  
Ab Initio ◽  
Phonon Scattering ◽  
Carrier Dynamics ◽  
Hot Electrons ◽  
Hot Electron ◽  
Hot Carriers ◽  
Hot Carrier ◽  
Acoustic Modes ◽  
Decay Times ◽  
Electron Phonon Scattering

Hot carrier dynamics critically impacts the performance of electronic, optoelectronic, photovoltaic, and plasmonic devices. Hot carriers lose energy over nanometer lengths and picosecond timescales and thus are challenging to study experimentally, whereas calculations of hot carrier dynamics are cumbersome and dominated by empirical approaches. In this work, we present ab initio calculations of hot electrons in gallium arsenide (GaAs) using density functional theory and many-body perturbation theory. Our computed electron–phonon relaxation times at the onset of the Γ, L, and X valleys are in excellent agreement with ultrafast optical experiments and show that the ultrafast (tens of femtoseconds) hot electron decay times observed experimentally arise from electron–phonon scattering. This result is an important advance to resolve a controversy on hot electron cooling in GaAs. We further find that, contrary to common notions, all optical and acoustic modes contribute substantially to electron–phonon scattering, with a dominant contribution from transverse acoustic modes. This work provides definitive microscopic insight into hot electrons in GaAs and enables accurate ab initio computation of hot carriers in advanced materials.

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