Optimizing Ga-profiles for highly efficient Cu(In, Ga)Se<sub>2</sub>thin film solar cells in simple and complex defect models

Frisk, Christopher; Platzer‐Björkman, Charlotte; Olsson, Jörgen; Szaniawski, Piotr; Wätjen, Jörn Timo; Fjällström, Viktor; Salomé, Pedro M. P.; Edoff, Marika

doi:10.1088/0022-3727/47/48/485104

Cited by 92 publications

(72 citation statements)

References 25 publications

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“…However, we note that there is a difference of 89 mV between both devices in V OC . Therefore, it can be concluded that the effect of introducing the point contact layer increases device performance by somewhat increasing the rear reflection but also significantly by the effect of its electronic passivation role, in agreement with our previous studies [20,89] and contrary to other data interpretation from the literature. Using the well-known equation that relates V OC with FF [72,73] www.advmatinterfaces.de the temperature, and q the electron charge, and considering the ideality values, A, of 0.92 and 1.13 for the reference and the passivated cell, respectively, it is possible to estimate that the passivated device should have a FF value around 3% higher than the passivated solar cell due to its higher V OC value.…”

Section: Discussionsupporting

confidence: 91%

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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Section: Discussionsupporting

confidence: 91%

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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“…Here, ф m is the work‐function of metal aluminium with an average of 4.17 eV . E g is the bandgap of CIGS (1.15 eV), and χ is electron affinity which was taken to be in the range of 3.9–4.5 eV . ф fp was calculated for an acceptor concentration of N a = 5 × 10 15 cm −3 and intrinsic carrier concentration ( n i ) of 7 × 10 8 cm −3 .…”

Section: Methodsmentioning

confidence: 99%

“…ф fp was calculated for an acceptor concentration of N a = 5 × 10 15 cm −3 and intrinsic carrier concentration ( n i ) of 7 × 10 8 cm −3 . n i was calculated from conduction‐band density of states (N C = 7 × 10 17 cm −3 ) and valence‐band density of states (N V = 1.5 × 10 19 cm −3 ) and k being the Boltzmann constant …”

Section: Methodsmentioning

confidence: 99%

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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“…The defect density of the CIGS layer as a function of Ga composition was also applied to the simulation. We referred to model B of the results of Frisk et al [14]. We used a linear DGB structure of the CIGS layer with a ZnS buffer as [4][5][6], where the minimum bandgap of 1.1 eV is located at a depth of 0.25 μm in the CIGS from the interface of the ZnS buffer, and the maximum bandgap is 1.5 eV at a depth of 1.8 μm contacting the Mo layer as shown in Figure 1 …”

Section: Experiments and Simulationsmentioning

confidence: 99%

Numerical Optimization of Gradient Bandgap Structure for CIGS Solar Cell with ZnS Buffer Layer Using Technology Computer-Aided Design Simulation

Park

Shin

2018

Energies

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Abstract:The band structure characteristics of a copper indium gallium sulfur selenide (Cu(In 1-x Ga x )SeS, CIGS) solar cell incorporating a cadmium-free zinc sulfide (ZnS) buffer layer were investigated using technology computer-aided design simulations. Considering the optical/electrical properties that depend on the Ga content, we numerically demonstrated that the front gradient bandgap enhanced the electron movement over the band-offset of the ZnS interface barrier, and the back gradient bandgap generated a back side field, improving electron transport in the CIGS layer; in addition, the short circuit current density (J SC ) and open circuit voltage (V OC ) improved. The simulation demonstrated that the conversion efficiency of a double graded bandgap cell is higher than with uniform or normal/reverse gradient cells, and V OC strongly correlated with the average bandgap in the space charge region (SCR) of CIGS. After selecting V OC from the SCR, we optimized the band structure of the CIGS cell with a Cd-free ZnS buffer by evaluating J SC and the fill factor. We demonstrated that the cell efficiency of the fabricated cell was more than 15%, which agrees well with the simulated results. Our numerical method can be used to design high-conversion efficiency CIGS cells with a gradient band structure and Cd-free buffer layer.

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Optimizing Ga-profiles for highly efficient Cu(In, Ga)Se₂thin film solar cells in simple and complex defect models

Cited by 92 publications

References 25 publications

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

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

Surface Passivation of CIGS Solar Cells Using Gallium Oxide

Numerical Optimization of Gradient Bandgap Structure for CIGS Solar Cell with ZnS Buffer Layer Using Technology Computer-Aided Design Simulation

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Optimizing Ga-profiles for highly efficient Cu(In, Ga)Se2thin film solar cells in simple and complex defect models

Cited by 92 publications

References 25 publications

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

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

Surface Passivation of CIGS Solar Cells Using Gallium Oxide

Numerical Optimization of Gradient Bandgap Structure for CIGS Solar Cell with ZnS Buffer Layer Using Technology Computer-Aided Design Simulation

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Optimizing Ga-profiles for highly efficient Cu(In, Ga)Se₂thin film solar cells in simple and complex defect models