Highly reflective rear surface passivation design for ultra-thin Cu(In,Ga)Se 2 solar cells

Vermang, Bart; Wätjen, Jörn Timo; Fjällström, Viktor; Rostvall, Fredrik; Edoff, Marika; Gunnarsson, Rickard; Pilch, Iris; Helmersson, Ulf; Kotipalli, Raja Venkata Ratan; Henry, F.; Flandre, Denis

doi:10.1016/j.tsf.2014.10.050

Cited by 52 publications

(61 citation statements)

References 7 publications

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“…1c) As reduction of the absorber thickness is expected to enhance the effect of undesired charge carrier recombination at the back-contact, an Al 2 O 3 passivation layer was prepared by a simple, self-organized spray-pyrolysis process onto the transparent back-contact prior to Cu(In,Ga)Se 2 deposition. Following the concept of a porous Al 2 O 3 back-contact passivation layer demonstrated for Cu(In,Ga)Se 2 solar cells with an opaque Mo back-contact by Vermang et al [4]- [6], an increase in V OC is expected for decreased charge carrier recombination at the back-contact. To test the Al 2 O 3 layer prepared by a self-organized spray-pyrolysis process as back contact passivation, solar cells with submicron Cu(In,Ga)Se 2 absorber were prepared on the SnO 2 :F back-contact with Al 2 O 3 layer and for comparison on the bare SnO 2 :F backcontact.…”

Section: Resultsmentioning

confidence: 99%

“…Based on concepts previously used for Sisolar cells, Vermang et al recently applied porous Al 2 O 3 passivation layers to reduce recombination losses at the opaque Mo-back-contact of solar cells with submicron Cu(In,Ga)Se 2 absorber thickness. In these Cu(In,Ga)Se 2 solar cells, the Al 2 O 3 passivation layers were demonstrated to result in an increased open circuit voltage V OC and thus, power conversion efficiency η [4]- [6].…”

Section: Introductionmentioning

confidence: 99%

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Bifacial Cu(In,Ga)Se2 solar cells with submicron absorber thickness: back-contact passivation and light management

Ohm

Riedel

Aksünger

et al. 2015

2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC)

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For bifacial Cu(In,Ga)Se 2 solar cells with submicron absorber thickness, an Al 2 O 3 -layer deposited by a simple, self-organized spray-pyrolysis process onto the transparent SnO 2 :F back-contact is used to increase open circuit voltage and thereby increase power conversion efficiency, especially for rear-illumination, indicating reduced charge carrier back-contact recombination. On non-passivated SnO 2 :F, a thin (10nm) Mo-layer improved the electrical back-contact properties, while on Al 2 O 3 -passivated SnO 2 :F, the solar cell performance was higher without Mo-modification. However, even with Momodification, the solar cell performance increased for Al 2 O 3 -passivated compared to non-passivated back-contacts demonstrating the benefit of the Al 2 O 3 -layer for bifacial solar cells with submicron Cu(In,Ga)Se 2 absorber layers.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bifacial Cu(In,Ga)Se2 solar cells with submicron absorber thickness: back-contact passivation and light management

Ohm

Riedel

Aksünger

et al. 2015

2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC)

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“…[2] Gallium grading has also been proposed to avoid minority carrier loss to the back contact. [3] We examined the sensitivity of the randomly textured CIGS device with 700 nm planar equivalent thickness to this offset in Figure S3. A −0.2 eV offset corresponds to a ∼50 mV loss in V OC compared to a V OC of 651 mV for zero band offset.…”

Section: Si3: Cigs|mo Band Offsetmentioning

confidence: 99%

Photon and carrier management design for nonplanar thin-film copper indium gallium selenide photovoltaics

Bukowsky

Grandidier

Fountaine

et al. 2017

Solar Energy Materials and Solar Cells

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Because it is commonly employed in experimental devices and in order to find an upper limit of device performance for the electrical parameters used, the optimum MgF 2 Anti-Reflection Coating (ARC) thickness was found by optimizing for photocurrent absorbed in the CIGS material. For planar and structured devices, the optimum thickness was 110 nm, while for the periodic device, the optimum was 166 nm. Figure S1a compares the 700 nm device with ARC (cp. Structured device with t=0 nm), the 1.7 µm device with ARC (cp. Structured device with t=1000 nm), and a planar 2.9 µm device with ARC. The 2.9 µm planar device with ARC was the optimal CIGS thickness found by parameterizing the CIGS thickness with the figure of merit being effciency in order to compare to the devices studied. Figure S1b shows that when adding the dielectric spacer layer to devices with optimized ARC, the thin planar device out-performs the optimized planar device in the case of perfect CIGS|SiO 2 interface passivation. The decreased reflection in the planar 700 nm device increases the current, and therefore efficiency, compared to Figure 4. The same is true of the other devices. The randomly textured device performs best of the three. These curves show the added benefit of dielectric layers, but also recognize that if suffciently low interface SRVs cannot be acheived, the optimum device will still be a thick planar device with ARC. Figure S1c shows the CIGS absorption when the ARC is applied. Compared to Figure 3c, the optimum ARC for planar and structured devices maximizes absorption near the peak of the photocurrent flux in the solar spectrum between 600-800 nm, with the optimum ARC coating being 110 nm thick. The periodic Figure S1: Devices with Anti-Reflection Coatings a) The JV curves of planar device with 110 nm MgF 2 ARC. The thicker optimized 2.9 µm device shows a minor improvement over the 1.7 µm textured device, corresponding to the planar equivalent thickness of a textured device with t=1000 nm b) The planar, periodic, and textured devices with a 190 nm dielectric layer at the back-contact and ARC outperform even the optimized planar device. Inset of a) and b) show the J-V parameters of the devices. c) the CIGS absorption spectra for the ARC coated devices in b).

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“…However, the open circuit voltage decreased. Over all, the addition of molybdenum particles (and a thin Al2O3 passivation layer) increased the cells average efficiency from 8.4± 1.3 to 8.8± 0.8 % [70]. This shows the feasibility of applying this technique to photovoltaic applications.…”

Section: Solar Cells With Molybdenum Particlesmentioning

confidence: 78%

“…One reason for this is the low internal reflection between the CIGS layer and the material it is deposited on (in this case a molybdenum thin film). The idea of this work was to scatter the incoming light on molybdenum particles embedded inside the CIGS layer, effectively increasing the distance the light travels in the solar cell [70]. The requirement specification for this to function was a monolayer of particles with a size in the order of 150 -200 nm that are also well separated from each other.…”

Section: Solar Cells With Molybdenum Particlesmentioning

confidence: 99%

Controlling the growth of nanoparticles produced in a highpower pulsed plasma

Gunnarsson¹

Self Cite

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Nanotechnology can profoundly benefit our health, environment and everyday life. In order to make this a reality, both technological and theoretical advancements of the nanomaterial synthesis methods are needed. A nanoparticle is one of the fundamental building blocks in nanotechnology and this thesis describes the control of the nucleation, growth and oxidation of titanium particles produced in a pulsed plasma. It will be shown that by controlling the process conditions both the composition (oxidation state) and size of the particles can be varied. The experimental results are supported by theoretical modeling.If processing conditions are chosen which give a high temperature in the nanoparticle growth environment, oxygen was found to be necessary in order to nucleate the nanoparticles. The two reasons for this are 1: the lower vapor pressure of a titanium oxide cluster compared to a titanium cluster, meaning a lower probability of evaporation, and 2: the ability of a cluster to cool down by ejecting an oxygen atom when an oxygen molecule condenses on its surface. When the oxygen gas flow was slightly increased, the nanoparticle yield and oxidation state increased. A further increase caused a decrease in particle yield which is attributed to a slight oxidation of the cathode. By varying the oxygen flow, it was possible to control the oxidation state of the nanoparticles without fully oxidizing the cathode. Pure titanium nanoparticles could not be produced in a high vacuum system because oxygen containing gases such as residual water vapour have a profound influence on nanoparticle yield and composition. In an ultrahigh vacuum system titanium nanoparticles without significant oxygen contamination were produced by reducing the temperature of the growth environment and increasing the pressure of an argon-helium gas mixture within which the nanoparticles grew. The dimer formation rate necessary for this is only achievable at higher pressures. After a dimer has formed, it needs to grow by colliding with a titanium atom followed by cooling by collisions with multiple buffer gas atoms. The condensation event heats up the cluster to a temperature much higher than the gas temperature, where it is during a short time susceptible to evaporation. When the clusters' internal energy has decreased by collisions with the gas to less than the energy required to evaporate a titanium atom, it is temporarily stable until the next condensation event occurs. The temperature difference by which the cluster has to cool down before it is temporarily stable is exactly as many kelvins as the gas temperature. The addition of helium was found to decrease the temperature of the gas, making it possible for nanoparticles of pure titanium to grow. The process window where this is possible was determined and the results presented opens up new iv possibilities to synthesize particles with a controlled contamination level and deposition rate.The size of the nanoparticles has been controlled by three means. The first is to change the electr...

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Highly reflective rear surface passivation design for ultra-thin Cu(In,Ga)Se 2 solar cells

Cited by 52 publications

References 7 publications

Bifacial Cu(In,Ga)Se2 solar cells with submicron absorber thickness: back-contact passivation and light management

Bifacial Cu(In,Ga)Se2 solar cells with submicron absorber thickness: back-contact passivation and light management

Photon and carrier management design for nonplanar thin-film copper indium gallium selenide photovoltaics

Controlling the growth of nanoparticles produced in a highpower pulsed plasma

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