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 23 publications

(44 citation statements)

References 31 publications

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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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Microstructural Passivation of Patterned Al₂O₃ Back Contacts on CdS/CdTe Solar Cells

Roy,

Mamun,

Lee

et al. 2024

Adv Materials Inter

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Patterned aluminum oxide (Al2O3) back contact on cadmium telluride (CdTe) solar cells can effectively mitigate the loss of the majority carriers while retaining the passivation benefits for minority carriers. This study investigates the impact of the point‐contact geometry on cell performance, where the spacing of the microholes is systematically varied at a constant microhole diameter (≈16 µm). Microhole arrays are created on an evaporated Al2O3 layer (≈30 nm) on CdTe using laser‐beam lithography and selective wet etching processes. Comparative analysis indicates a significant decrease in fill factor (FF) and short‐circuit current (ISC) when the contact fraction falls below 30%, likely due to the Al2O3 barrier impeding majority carriers. Above this fraction, FF and ISC are comparable to those of baseline CdTe cells without Al2O3. Open‐circuit voltage (VOC) shows a gradual decrease as Al2O3 coverage is reduced but exhibits a slight increase (<15 mV) when the contact fraction exceeds 30%. Cathodoluminescence (CL) characterization reveals that significantly improved radiative recombination occurs within the CdTe grain bulk with Al2O3, whereas this effect on grain boundaries is minimal. The findings imply complex local carrier dynamics in the patterned back‐contact region, closely tied to the microstructural properties of CdTe‐based solar cells.

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

Cited by 23 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

Microstructural Passivation of Patterned Al₂O₃ Back Contacts on CdS/CdTe Solar Cells

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

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

Cited by 23 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

Microstructural Passivation of Patterned Al2O3 Back Contacts on CdS/CdTe Solar Cells

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

Contact Info

Product

Resources

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Microstructural Passivation of Patterned Al₂O₃ Back Contacts on CdS/CdTe Solar Cells