Charged grain boundaries reduce the open-circuit voltage of polycrystalline solar cells—An analytical description

Gaury, Benoit; Haney, Paul M.

doi:10.1063/1.4972028

Cited by 21 publications

(44 citation statements)

References 31 publications

(36 reference statements)

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“…This latter case was studied in detail in Ref. 12. This mapping from a continuum of donor+acceptor states to a single donor+acceptor state is valid for values of α such that the densities of donor and acceptor states remain commensurate [25].…”

Section: Physical Model Of the Grain Boundarymentioning

confidence: 99%

“…A direct analytical solution for the full two-dimensional problem is not feasible. To make analytical progress, we split the two-dimensional system into two onedimensional sub-systems: the grain boundary core where electrons are electrostatically confined [5,12,27], and the grain interior (grain boundary free pn junction) where a solution is known. Our approach relies on approximations (or assumptions) which connect these two problems, and render the continuity-Poisson equations along the grain boundary core analytically tractable.…”

Section: B Assumptions In the Nonequilibrium Analysismentioning

confidence: 99%

“…As discussed in Sec. III, for this case f 0 remains fixed by keeping [12]. In the grain interior of the pregion, the increase of voltage V shifts the electron quasi-Fermi level from the valence band by an amount qV .…”

Section: A Grain Boundary Recombination Formentioning

confidence: 99%

“…In light of the need for improved understanding of grain boundaries' impact on V oc , we recently developed an analytical description of dark grain boundary recombination current, with the primary result of a simple relation between grain boundary properties and V oc [12]. Some details of the grain boundary model in this previous work are rather particular: we assumed that the grain boundary defect states consist of a donor and an acceptor at the same energy (so-called negative U-center).…”

Section: Introductionmentioning

confidence: 99%

“…We found that generalizing the grain boundary defect configurations necessitated a clearer and more general formulation of the model assumptions given in Ref. 12. The scope of this analysis is limited to grains with interior electrostatically similar to the unperturbed (i.e.…”

Section: Introductionmentioning

confidence: 99%

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Charged Grain Boundaries and Carrier Recombination in Polycrystalline Thin-Film Solar Cells

Gaury

Haney

2017

Phys. Rev. Applied

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We present analytical relations for the dark recombination current of a pn + junction with positively charged columnar grain boundaries in the high defect density regime. We consider two defect state configurations relevant for positively charged grain boundaries: a single donor state and a continuum of both acceptors and donors. Compared to a continuum of acceptor+donor states, or to the previously studied single acceptor+donor state, the grain boundary recombination of a single donor state is suppressed by orders of magnitude. We show numerically that superposition holds near the open-circuit voltage Voc, so that our dark J(V ) relations determine Voc for a given short circuit current Jsc. We finally explicitly show how Voc depends on the these two grain boundary defect state configurations.

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Section: Physical Model Of the Grain Boundarymentioning

confidence: 99%

Section: B Assumptions In the Nonequilibrium Analysismentioning

confidence: 99%

Section: A Grain Boundary Recombination Formentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Charged Grain Boundaries and Carrier Recombination in Polycrystalline Thin-Film Solar Cells

Gaury

Haney

2017

Phys. Rev. Applied

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Obtaining Large Columnar CdTe Grains and Long Lifetime on Nanocrystalline CdSe, MgZnO, or CdS Layers

Amarasinghe

Colegrove

Moseley

et al. 2018

Advanced Energy Materials

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CdTe solar cells have reached efficiencies comparable to multicrystalline silicon and produce electricity at costs competitive with traditional energy sources. Recent efficiency gains have come partly from shifting from the traditional CdS window layer to new materials such as CdSe and MgZnO, yet substantial headroom still exists to improve performance. Thin film technologies including Cu(In,Ga)Se 2 , perovskites, Cu 2 ZnSn(S,Se) 4 and CdTe inherently have many grain boundaries that can form recombination centers and impede carrier transport, however grain boundary engineering has been difficult and not practical. In this work, we demonstrate that wide columnar grains reaching through the entire CdTe layer can be achieved by aggressive postdeposition CdTe recrystallization. This reduces the grain structure constraints imposed by nucleation on nanocrystalline window layers, and enables diverse window layers to be selected for other properties critical for electro-optical This article is protected by copyright. All rights reserved. 2 applications. Computational simulations indicate that increasing grain size from 1 to 7 μm can be equivalent to decreasing grain-boundary recombination velocity by three orders of magnitude. Here, large high-quality grains enable CdTe lifetimes exceeding 50 ns.

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Impact of Grain Size and Grain Nature in Thin‐Film Solar Cells

Prabu,

Malathi,

Kumar

et al. 2023

Energy Tech

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Herein, a theoretical investigation is conducted on grain‐size inhomogeneity's impact and grain boundaries’ (GBs’) electrical nature in thin‐film solar cells. Using the Matthiessen rule, grain‐size‐dependent mobility is derived in polycrystalline material. The obtained grain‐size‐dependent mobility values are fed into the Poisson solver to calculate device performance. The severity of grain sizes in the lower region determines how grain size affects the photovoltaic performance by grain‐size‐dependent efficiency simulation. Low grain sizes become critical, especially for low‐thickness absorbers. The second aspect of the study assesses potential variation at GBs to reveal the impact of the electrical properties of GBs. Evidence shows that the acceptor defects at GB are benign for device performance, causing upward band bending at the GB and acting as electron barriers. Device performance is adversely affected by donor defects at GBs due to downward band bending. As summarized in the findings, the polycrystallinity‐induced cause–effect relationships of grains are likely to interest solar cell researchers.

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Charged grain boundaries reduce the open-circuit voltage of polycrystalline solar cells—An analytical description

Cited by 21 publications

References 31 publications

Charged Grain Boundaries and Carrier Recombination in Polycrystalline Thin-Film Solar Cells

Charged Grain Boundaries and Carrier Recombination in Polycrystalline Thin-Film Solar Cells

Obtaining Large Columnar CdTe Grains and Long Lifetime on Nanocrystalline CdSe, MgZnO, or CdS Layers

Impact of Grain Size and Grain Nature in Thin‐Film Solar Cells

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