CarrierCapture.jl: Anharmonic Carrier Capture

Kim, Sung-Hyun; Hood, Samantha N.; Gerwen, Puck van; Whalley, Lucy D.; Walsh, Aron

doi:10.21105/joss.02102

Cited by 29 publications

(33 citation statements)

References 6 publications

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“…Even in a single plane, due to the presence of MA, the initial and final states differ in energy by 60 meV, which supports the first disorder explanation. We further determine the vibrational frequency at T = 300 K around using CarrierCapture 92 . Effective frequencies of 0.4–0.7 THz represent the curvature of the potential energy surface along the directions of ion diffusion.…”

Section: Resultsmentioning

confidence: 99%

Probing the ionic defect landscape in halide perovskite solar cells

Reichert

Woo

et al. 2020

Nat Commun

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Point defects in metal halide perovskites play a critical role in determining their properties and optoelectronic performance; however, many open questions remain unanswered. In this work, we apply impedance spectroscopy and deep-level transient spectroscopy to characterize the ionic defect landscape in methylammonium lead triiodide (MAPbI3) perovskites in which defects were purposely introduced by fractionally changing the precursor stoichiometry. Our results highlight the profound influence of defects on the electronic landscape, exemplified by their impact on the device built-in potential, and consequently, the open-circuit voltage. Even low ion densities can have an impact on the electronic landscape when both cations and anions are considered as mobile. Moreover, we find that all measured ionic defects fulfil the Meyer–Neldel rule with a characteristic energy connected to the underlying ion hopping process. These findings support a general categorization of defects in halide perovskite compounds.

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Section: Resultsmentioning

confidence: 99%

Probing the ionic defect landscape in halide perovskite solar cells

Reichert

Woo

et al. 2020

Nat Commun

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“…To determine the non-radiative recombination activity, electron and hole capture coefficients were calculated for each charge state of the defect. This approach, building on the developments of Alkauskas et al, 60 uses the CarrierCapture.jl package, 61 and full details of the calculation procedure are provided in the Supporting Information, Section S8 . The PES of the defect is mapped along the structural path (configuration coordinate) Q between the equilibrium geometries for a given charge transition, from which nuclear wave function overlaps can be determined via the 1D Schrödinger equation.…”

Section: Trap-mediated Recombinationmentioning

confidence: 99%

Rapid Recombination by Cadmium Vacancies in CdTe

2021

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CdTe is currently the largest thin-film photovoltaic technology. Non-radiative electron–hole recombination reduces the solar conversion efficiency from an ideal value of 32% to a current champion performance of 22%. The cadmium vacancy (V Cd ) is a prominent acceptor species in p -type CdTe; however, debate continues regarding its structural and electronic behavior. Using ab initio defect techniques, we calculate a negative-U double-acceptor level for V Cd , while reproducing the V Cd 1– hole–polaron, reconciling theoretical predictions with experimental observations. We find the cadmium vacancy facilitates rapid charge-carrier recombination, reducing maximum power-conversion efficiency by over 5% for untreated CdTe—a consequence of tellurium dimerization, metastable structural arrangements, and anharmonic potential energy surfaces for carrier capture.

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“…The potential energy surfaces (PESs) in the CC diagrams were calculated by linearly interpolating the ground-state structures of the defect in the initial and final charge state, and computing the energy in the range −1.5 to 1.5 × Q with steps of 0.1 × Q, where Q is the difference in CC of the structures. We have calculated the vibrational wave functions χ and overlap integrals χ em |χ gn , where m and n are the vibrational levels of the excited (e) and ground (g) state, from solutions of the Schrödinger equation for the calculated PESs by using a finite-difference method, as implemented in CarrierCapture.jl [51].…”

Section: A Computational Detailsmentioning

confidence: 99%

Broad luminescence from donor-complexed LiZn and NaZn acceptors in ZnO

et al. 2019

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Zn substitutional lithium (Li Zn) and sodium (Na Zn) acceptors and their complexes with common donor impurities (Al Zn , H i , and H O) in ZnO have been studied using hybrid functional calculations. The results show that the complexes are not exclusively charge neutral, but rather exhibit a thermodynamic (+/0) transition level close to the valence band maximum. The positive charge states are associated with a polaronic defect state, similar to those of the well-studied charge-neutral isolated acceptors. This incomplete passivation has profound consequences for the optical properties of the complexes. Indeed, electron transitions from the conduction band minimum to the (+/0) transition level of the complexes result in broad luminescence bands that are blueshifted with respect to those originating from the isolated acceptors. Such complexes are proposed as a potential defect origin of the green luminescence observed at the high-energy side of the orange luminescence band (caused by Li Zn) in hydrothermally grown ZnO. This prediction is supported by experimental photoluminescence and secondary ion mass spectrometry data on a hydrothermally grown ZnO sample. We have also explored how the parameters controlling the fraction and screening of exchange in the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional influence the results by comparing two parametrization approaches: (i) the conventional one where the exchange fraction is adjusted to reproduce the experimental band gap, and (ii) tuning both parameters in order to also comply with the generalized Koopmans theorem (gKT). Interestingly, these approaches were found to yield similar results.

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CarrierCapture.jl: Anharmonic Carrier Capture

Cited by 29 publications

References 6 publications

Probing the ionic defect landscape in halide perovskite solar cells

Probing the ionic defect landscape in halide perovskite solar cells

Rapid Recombination by Cadmium Vacancies in CdTe

Broad luminescence from donor-complexed LiZn and NaZn acceptors in ZnO

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