Impact of front-side point contact/passivation geometry on thin-film solar cell performance

Sozzi, Giovanna; Napoli, Simone Di; Menozzi, Roberto; Bissig, Benjamin; Buecheler, Stephan; Tiwari, Ayodhya N.

doi:10.1016/j.solmat.2017.02.031

Cited by 42 publications

(46 citation statements)

References 49 publications

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“…Since the doping levels in CIGSe material of these experiments are comparatively low (10 15 cm −3 ), an oxide with positive charge could form a depletion layer and improve charge collection at the front CIGS‐CdS interface. This effect has been theoretically studied by Sozzi et al and Bercegol et al In contrast, AlO x shows high negative charge densities between −2 × 10 11 to −1 × 10 12 which is consistent with previous observations …”

Section: Methodssupporting

confidence: 91%

“…The electrical characterization of these cells did indeed show an absolute increase of 2.6% in efficiency originating from a substantial increase of 56.3 mV in V OC , 1.04 mA cm −2 in J SC , and 8.22% in FF with a gallium oxide layer as compared to the reference. Therefore as an outlook, future experiments can focus on alternative buffer layers or deposition techniques, point contact openings through thick gallium oxide layers (such as those simulated by Sozzi et al and Bercegol et al,) and also low‐temperature conductance measurements on MIS structures to quantify D it .…”

Section: Resultsmentioning

confidence: 99%

“…This can be due to a “chemical passivation” which reduces dangling bonds and active interface defects. It may also be due to a “field‐effect passivation” which can, based on the polarity of charges in the region, either repel minority charge carriers and reduce recombination or repel majority carriers sufficiently to cause an inversion at the surface …”

Section: Introductionmentioning

confidence: 99%

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Surface Passivation of CIGS Solar Cells Using Gallium Oxide

Garud

Gampa

Allen

et al. 2018

Physica Status Solidi (a)

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This work proposes gallium oxide grown by plasma‐enhanced atomic layer deposition, as a surface passivation material at the CdS buffer interface of Cu(In,Ga)Se2 (CIGS) solar cells. In preliminary experiments, a metal‐insulator‐semiconductor (MIS) structure is used to compare aluminium oxide, gallium oxide, and hafnium oxide as passivation layers at the CIGS‐CdS interface. The findings suggest that gallium oxide on CIGS may show a density of positive charges and qualitatively, the least interface trap density. Subsequent solar cell results with an estimated 0.5 nm passivation layer show an substantial absolute improvement of 56 mV in open‐circuit voltage (VOC), 1 mA cm−2 in short‐circuit current density (JSC), and 2.6% in overall efficiency as compared to a reference (with the reference showing 8.5% under AM 1.5G).

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Section: Methodssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Surface Passivation of CIGS Solar Cells Using Gallium Oxide

Garud

Gampa

Allen

et al. 2018

Physica Status Solidi (a)

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“…More details on the two-dimensional simulations can be found in an earlier publication [33]. Structures with 100 nm width were simulated, comprising a double-graded CIGS absorber divided into two areas with a low-bandgap and a higher-bandgap grading, with widths of 85 nm and 15 nm, respectively.…”

Section: Discussionmentioning

confidence: 99%

Voids and compositional inhomogeneities in Cu(In,Ga)Se₂ thin films: evolution during growth and impact on solar cell performance

Avancini

Keller

Carron

et al. 2018

Science and Technology of Advanced Materials

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Structural defects such as voids and compositional inhomogeneities may affect the performance of Cu(In,Ga)Se2 (CIGS) solar cells. We analyzed the morphology and elemental distributions in co-evaporated CIGS thin films at the different stages of the CIGS growth by energy-dispersive x-ray spectroscopy in a transmission electron microscope. Accumulation of Cu-Se phases was found at crevices and at grain boundaries after the Cu-rich intermediate stage of the CIGS deposition sequence. It was found, that voids are caused by Cu out-diffusion from crevices and GBs during the final deposition stage. The Cu inhomogeneities lead to non-uniform diffusivities of In and Ga, resulting in lateral inhomogeneities of the In and Ga distribution. Two and three-dimensional simulations were used to investigate the impact of the inhomogeneities and voids on the solar cell performance. A significant impact of voids was found, indicating that the unpassivated voids reduce the open-circuit voltage and fill factor due to the introduction of free surfaces with high recombination velocities close to the CIGS/CdS junction. We thus suggest that voids, and possibly inhomogeneities, limit the efficiency of solar cells based on three-stage co-evaporated CIGS thin films. Passivation of the voids’ internal surface may reduce their detrimental effects.

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“…Simply, the chemical passivation allows for the decrease of the total number of electrically active defects. [38][39][40][41] Ultrathin devices have recently been studied in detail by numerous groups [42][43][44][45][46][47] as they have the potential to reduce the material costs and manufacturing times. Such field is beneficial for the electrical performance of the solar cell, since it drives minority carriers away from the highly recombinative rear contact into the space charge region.…”

Section: Introductionmentioning

confidence: 99%

Passivation of Interfaces in Thin Film Solar Cells: Understanding the Effects of a Nanostructured Rear Point Contact Layer

Salomé

Vermang

Ribeiro‐Andrade

et al. 2017

Adv Materials Inter

110

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Thin film solar cells based in Cu(In,Ga)Se2 (CIGS) are among the most efficient polycrystalline solar cells, surpassing CdTe and even polycrystalline silicon solar cells. For further developments, the CIGS technology has to start incorporating different solar cell architectures and strategies that allow for very low interface recombination. In this work, ultrathin 350 nm CIGS solar cells with a rear interface passivation strategy are studied and characterized. The rear passivation is achieved using an Al2O3 nanopatterned point structure. Using the cell results, photoluminescence measurements, and detailed optical simulations based on the experimental results, it is shown that by including the nanopatterned point contact structure, the interface defect concentration lowers, which ultimately leads to an increase of solar cell electrical performance mostly by increase of the open circuit voltage. Gains to the short circuit current are distributed between an increased rear optical reflection and also due to electrical effects. The approach of mixing several techniques allows us to make a discussion considering the different passivation gains, which has not been done in detail in previous works. A solar cell with a nanopatterned rear contact and a 350 nm thick CIGS absorber provides an average power conversion efficiency close to 10%.

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Impact of front-side point contact/passivation geometry on thin-film solar cell performance

Cited by 42 publications

References 49 publications

Surface Passivation of CIGS Solar Cells Using Gallium Oxide

Surface Passivation of CIGS Solar Cells Using Gallium Oxide

Voids and compositional inhomogeneities in Cu(In,Ga)Se₂ thin films: evolution during growth and impact on solar cell performance

Passivation of Interfaces in Thin Film Solar Cells: Understanding the Effects of a Nanostructured Rear Point Contact Layer

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Impact of front-side point contact/passivation geometry on thin-film solar cell performance

Cited by 42 publications

References 49 publications

Surface Passivation of CIGS Solar Cells Using Gallium Oxide

Surface Passivation of CIGS Solar Cells Using Gallium Oxide

Voids and compositional inhomogeneities in Cu(In,Ga)Se2 thin films: evolution during growth and impact on solar cell performance

Passivation of Interfaces in Thin Film Solar Cells: Understanding the Effects of a Nanostructured Rear Point Contact Layer

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Product

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Voids and compositional inhomogeneities in Cu(In,Ga)Se₂ thin films: evolution during growth and impact on solar cell performance