How Polycrystalline Devices Can Outperform Single‐Crystal Ones: Thin Film CdTe/CdS Solar Cells

Visoly‐Fisher, Iris; Cohen, Sidney R.; Ruzin, A.; Cahen, David

doi:10.1002/adma.200306624

Cited by 177 publications

(131 citation statements)

References 32 publications

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“…3). This finding suggests that the grain boundaries do not contain significant depletion regions and that the electrical current is uniformly photo-generated in the bulk and at the interfaces of the ARTICLE grains, a situation quite different from that of CdTe but somewhat akin to that found for CIGS cells 22,23 . This may be the result of a low density of surface states, possibly due to the partial organic nature of this semiconductor, with the organic moieties passivating the surface (amines are well-known passivation agents for II-VI semiconductor surfaces).…”

Section: Resultsmentioning

confidence: 71%

Elucidating the charge carrier separation and working mechanism of CH3NH3PbI3−xClx perovskite solar cells

et al. 2014

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Developments in organic-inorganic lead halide-based perovskite solar cells have been meteoric over the last 2 years, with small-area efficiencies surpassing 15%. We address the fundamental issue of how these cells work by applying a scanning electron microscopy-based technique to cell cross-sections. By mapping the variation in efficiency of charge separation and collection in the cross-sections, we show the presence of two prime high efficiency locations, one at/near the absorber/hole-blocking-layer, and the second at/near the absorber/electron-blocking-layer interfaces, with the former more pronounced. This 'twin-peaks' profile is characteristic of a p-i-n solar cell, with a layer of low-doped, high electronic quality semiconductor, between a p-and an n-layer. If the electron blocker is replaced by a gold contact, only a heterojunction at the absorber/hole-blocking interface remains.

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Section: Resultsmentioning

confidence: 71%

Elucidating the charge carrier separation and working mechanism of CH3NH3PbI3−xClx perovskite solar cells

et al. 2014

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“…From the experimental evidence it appears that type inversion applies rather to CdTe solar cells 4,5 whereas in CIGS ͑Refs. 7-9, 12, 16, and 17͒ the band bending around the GB is relatively small.…”

Section: E Collection Of Carriers Along Grain Boundariesmentioning

confidence: 99%

Numerical simulation of carrier collection and recombination at grain boundaries in Cu(In,Ga)Se2 solar cells

Taretto

Rau

2008

Journal of Applied Physics

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Two-dimensional numerical device simulations investigate the influence of grain boundaries ͑GBs͒ on the performance of Cu͑In, Ga͒Se 2 solar cells. We find that the electronic activity of grain boundaries can reduce the efficiency of Cu͑In, Ga͒Se 2 solar cells from 20% to below 12% making proper passivation of GBs a primary requirement for high efficiency. Cell efficiencies larger than 19% require GB defect densities below 10 11 cm −2 . Also, an internal band offset in the valence band due to a Cu-poor region adjacent to the GBs could effectively passivate grain boundaries that are otherwise very recombination active. It is shown that such a barrier must be more than 300 meV high and at least 3 nm wide to virtually suppress all grain boundary recombination. Contrariwise, such a barrier represents an obstacle for hole transport reducing carrier collection across grain boundaries that are not perpendicular to the cell surface. We further find that inverted grain boundaries lead to an accumulation of the short circuit current along the grain boundary, which in certain situations enhances the total short circuit current. However, we do not find any beneficial effect of any type of grain boundaries on the overall cell efficiency.

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“…Work by Seger et al 28 and others [53][54][55] has shown that higher charge-collection efficiency in photovoltaics can be achieved with single crystal semiconductors compared to polycrystalline material due to reduced recombination as a result of fewer grain boundaries and surface defects. This nding extends to PEC water-splitting, which also involves the separation of photogenerated charges in semiconductors under illumination.…”

Section: Passivation Layer Suppression Of Surface Recombination and Imentioning

confidence: 99%

Enhanced photoelectrochemical water-splitting performance of semiconductors by surface passivation layers

Zheng

Spurgeon

et al. 2014

Energy Environ. Sci.

564

439

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An important approach for solving the world's sustainable energy challenges is the conversion of solar energy to chemical fuels. Semiconductors can be used to convert/store solar energy to chemical bonds in an energy-dense fuel. Photoelectrochemical (PEC) water-splitting cells, with semiconductor electrodes, use sunlight and water to generate hydrogen. Herein, recent studies on improving the efficiency of semiconductor-based solar water-splitting devices by the introduction of surface passivation layers are reviewed. We show that passivation layers have been used as an effective strategy to improve the charge-separation and transfer processes across semiconductor-liquid interfaces, and thereby increase overall solar energy conversion efficiencies. We also summarize the demonstrated passivation effects brought by these thin layers, which include reducing charge recombination at surface states, increasing the reaction kinetics, and protecting the semiconductor from chemical corrosion.These benefits of passivation layers play a crucial role in achieving highly efficient water-splitting devices in the near future. Broader contextSemiconductor interface is one of the most important components/regions in photoelectrochemical (PEC) water splitting devices. The serious surface charge recombination, slow charge transfer kinetics and the poor photoelectrochemical stability are the three main challenges for the practical PEC water splitting devices. Recently, the studies of constructing passivation layer onto the semiconductor to address these challenges have attracted increasing research attentions, due to the potential application of solar to chemical energy conversion. When these layers incorporated onto semiconductor surface, signicant changes of the interface would be found including charge transfer improvement, surface charge recombination, and chemical corrosion, etc. Although various strategies have been suggested for this surface modication, a synergetic effect must be achieved on an advanced photoelectrodes accounting for the improved solar-tohydrogen efficiencies. This review will shed light on the recent PEC water splitting work surface state passivation, corrosion retardation and charge transfer improvement in this passivation layer.

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How Polycrystalline Devices Can Outperform Single‐Crystal Ones: Thin Film CdTe/CdS Solar Cells

Cited by 177 publications

References 32 publications

Elucidating the charge carrier separation and working mechanism of CH3NH3PbI3−xClx perovskite solar cells

Elucidating the charge carrier separation and working mechanism of CH3NH3PbI3−xClx perovskite solar cells

Numerical simulation of carrier collection and recombination at grain boundaries in Cu(In,Ga)Se2 solar cells

Enhanced photoelectrochemical water-splitting performance of semiconductors by surface passivation layers

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