Dynamics of Charge Transfer and Multiple Exciton Generation in the Doped Silicon Quantum Dot–Carbon Nanotube System: Density Functional Theory-Based Computation
- North Dakota State Univ., Fargo, ND (United States)
In this study, we use the Boltzmann transport equation (BE) to study time evolution of a photoexcited state, including phonon-mediated exciton relaxation, multiple exciton generation (MEG), and energy-transfer processes. BE collision integrals are derived using Kadanoff–Baym–Keldysh many-body perturbation theory (MBPT) based on density functional theory (DFT) simulations, including exciton effects. We apply the method to a nanostructured p–n junction composed of a 1 nm hydrogen-terminated Si quantum dot (QD) doped with two phosphorus atoms (Si36P2H42) adjacent to the (6, 2) single-wall carbon nanotube (CNT) with two chlorine atoms per two unit cells adsorbed to the surface. We find that an initial excitation localized on either the QD or CNT evolves into a transient charge-transfer (CT) state where either electron or hole transfer has taken place. The CT state lifetime is about 40 fs. Also, we study MEG in this system by computing internal quantum efficiency (QE), which is the number of excitons generated from an absorbed photon during relaxation. We predict efficient MEG starting at 3Eg ≃ 1.5 eV and with QE reaching QE = 1.65 at about 5Eg, where Eg ≃ 0.5 eV is the lowest exciton energy, i.e., the gap. However, we find that including energy transfer and MEG effects suppresses CT state generation.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Univ. of California, Oakland, CA (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- AC02-05CH11231; SC00001717
- OSTI ID:
- 1543671
- Journal Information:
- Journal of Physical Chemistry Letters, Vol. 9, Issue 19; ISSN 1948-7185
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Photoexcited carrier dynamics in colloidal quantum dot solar cells: insights into individual quantum dots, quantum dot solid films and devices
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journal | January 2020 |
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