Bifacial semi-transparent ultra-thin Cu(In,Ga)Se2 solar cells on ITO substrate: How ITO thickness and Na doping influence the performance

Li, Y.; Yin, Guanchao; Schmid, Martina

doi:10.1016/j.solmat.2021.111431

Cited by 16 publications

(21 citation statements)

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“…Replacement of Mo by a semitransparent back contact in chalcopyrite devices has already been demonstrated using ITO, [9,[28][29][30][31] fluorine-doped SnO 2 (FTO), [9,28,32] AZO, [28,33] and hydrogen-doped In 2 O 3 (IOH). [34,35] In some of these cases, high-efficiency devices were obtained by applying bare ITO with a CIGSe coevaporation deposition temperature of 520 C (efficiency of 15.2%) [28] or bare IOH with a coevaporation deposition temperature of 550 C (up to 16.1% efficiency in (Ag,Cu)(In,Ga)Se 2 devices and 11% in Cu(In,Ga)Se 2 devices).…”

Section: Introductionmentioning

confidence: 99%

Characterization of the Stability of Indium Tin Oxide and Functional Layers for Semitransparent Back‐Contact Applications on Cu(in,Ga)Se₂Solar Cells

et al. 2022

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Herein, a detailed study of the stability of different ITO‐based back‐contact configurations (including bare ITO contacts and contacts functionalized with nanometric Mo, MoSe2, and MoS2 layers) under the coevaporation processes developed for the synthesis of high‐efficiency Cu(In,Ga)Se2 (CIGSe) solar cells is reported. The results show that bare ITO layers can be used as efficient back contacts for coevaporation process temperatures of 480 ºC. However, higher temperatures produce an amorphous In–Se phase at the ITO surface that reduces the contacts transparency in the visible region. This is accompanied by degradation of the solar cells’ efficiency. Inclusion of a Mo functional layer leads to the formation of a MoSe2 interfacial phase during the coevaporation process, which improves the cells’ efficiency, achieving device efficiencies similar to those obtained with reference solar cells fabricated with standard Mo back contacts. Optimization of the initial Mo layer thickness improves the contact transparency, achieving contacts with an optical transparency of 50% in the visible region. This is accompanied by a relevant decrease in back reflectivity in the CIGSe devices, confirming the potential of these contact configurations for the development of semitransparent CIGSe devices with improved optical aesthetic quality without compromising the device performance.

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Section: Introductionmentioning

confidence: 99%

Characterization of the Stability of Indium Tin Oxide and Functional Layers for Semitransparent Back‐Contact Applications on Cu(in,Ga)Se₂Solar Cells

et al. 2022

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“…For solar cells based on the thin‐film absorber Cu(In,Ga)Se 2 (CIGS), exclusively n‐type transparent conductive oxide (TCO) films have been tested as TBCs so far. This encompasses mainly fluorine‐doped SnO 2 (FTO), [ 1–8 ] tin‐ (ITO), [ 2,6,8–22 ] or hydrogen‐doped (IOH) [ 23,24 ] In 2 O 3 , and aluminum‐doped ZnO (AZO). [ 2,5,14,25,26 ]…”

Section: Introductionmentioning

confidence: 99%

“…For solar cells based on the thin-film absorber Cu(In,Ga)Se 2 (CIGS), exclusively n-type transparent conductive oxide (TCO) films have been tested as TBCs so far. This encompasses mainly fluorine-doped SnO 2 (FTO), [1][2][3][4][5][6][7][8] tin-(ITO), [2,6,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] or hydrogen-doped (IOH) [23,24] In 2 O 3 , and aluminum-doped ZnO (AZO). [2,5,14,25,26] The solar cells made on such TBCs usually show no clear trend/change in short-circuit current density ( J SC ) and open-circuit voltage (V OC ), but often a pronounced reduction in fill factor (FF) when exchanging the standard opaque Mo back contact with a TCO layer.…”

Section: Introductionmentioning

confidence: 99%

Wide‐Gap Chalcopyrite Solar Cells with Indium Oxide–Based Transparent Back Contacts

et al. 2022

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Herein, the performance of wide‐gap Cu(In,Ga)Se2 (CIGS) and (Ag,Cu)(In,Ga)Se2 (ACIGS) solar cells with In2O3:Sn (ITO) and In2O3:H (IOH) as transparent back contact (TBC) materials is evaluated. Since both TBCs restrict sodium in‐diffusion from the glass substrate, fine‐tuning of a NaF precursor layer is crucial. It is found that the optimum Na supply is lower for ACIGS than for CIGS samples. An excessive sodium amount deteriorates the solar cell performance, presumably by facilitating GaO x growth at the TBC/absorber interface. The efficiency (η) further depends on the absorber stoichiometry, with highest fill factors (and η) reached for close‐stoichiometric compositions. An ACIGS solar cell with η = 12% at a bandgap of 1.44 eV is processed, using IOH as a TBC. The best CIGS device reaches η = 11.2% on ITO. Due to its very high infrared transparency, IOH is judged superior to ITO for implementation in a top cell of a tandem device. However, while ITO layers maintain their conductivity, IOH films show an increased sheet resistance after absorber deposition. Chemical investigations indicate that incorporation of Se during the initial stage of absorber processing may be responsible for the deteriorated conductivity of the IOH back contact in the final device.

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“…[19][20][21][22] On the other hand, if the ultrathin CIGSe was fabricated on a transparent back contact, the ultrathin CIGSe SCs become semitransparent, and the unabsorbed part of the light can be utilized in other ways. [9,13,23,24] Furthermore, semitransparent SCs have abundant application scenarios, for example, building-integrated PV, agrivoltaics, and vehicle-integrated PV. In addition, it is compatible with laser scribing in module fabrication.…”

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confidence: 99%

“…Recently, we improved the front illumination open-circuit voltage (V oc ) of the ultrathin CIGSe SCs by optimizing the Na doping and by adjusting the ITO (In 2 O 3 :Sn) thickness to diminish the back contact potential barrier height E h . [24,34] Instead of other materials (such as ZnO:Al and In 2 O 3 :F), we chose ITO as the back contact for BSTUT CIGSe SCs because ITO can tolerate high temperature necessary for the sequential CIGSe co-evaporation process. At this stage, it is tempting to add the SiO 2 NPs to further improve the j sc of the BSTUT SCs and especially to explore the lighttrapping effects under rear illumination.…”

mentioning

confidence: 99%

Beyond Light‐Trapping Benefits: The Effect of SiO₂ Nanoparticles in Bifacial Semitransparent Ultrathin Cu(In,Ga)Se₂ Solar Cells

Tabernig

Yin

et al. 2022

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With carbon neutrality becoming a central request in economic development nowadays, green energy like photovoltaics (PV) stands in an increasingly prominent position. [1] Compared with silicon-based solar cells (SCs), polycrystalline thin-film SCs based on Cu(In,Ga)Se 2 (CIGSe) have many unique advantages such as smaller light-induced degradation and shorter energy payback time. [2][3][4][5] Those characteristics provide the CIGSe panels with a longer stable lifetime and lower fabrication cost. From the material point of view, because the defects in the chalcopyrite CIGSe act as effective doping, the error-tolerance toward defects introduced during the production process is high, which is advantageous for large-scale production. [6] In addition, the CIGSe bandgap E g can be tuned by adjusting the Ga/(Ga þ In) element ratio or by replacing In with Ga, Cu with Ag, and S with Se. Therefore, CIGSe can be flexible and applicable in tandem SCs. [7,8] Among the CIGSe SC family, ultrathin CIGSe (<500 nm) has drawn more and more attention recently. [9][10][11][12][13] One major reason is, if light management was applied properly, the ultrathin CIGSe SCs show an equally high theoretical conversion efficiency (Eff ) as the standard thick ones (%2000 nm) while reducing the raw material consumption, especially of the rare metal indium. [14][15][16] In laboratory experiments, 15% record efficiency has been achieved on Mo substrates. [17] In the state-of-the-art PV performance, the biggest difference between the ultrathin and the standard thick SCs is the short-circuit current density j sc . [5,17] The j sc is 26.4 mA cm À2 for an absorber thickness of 500 nm and 39.6 mA cm À2 for an absorber thickness of 2 μm. The reason for the drop in j sc is insufficient light absorption in the ultrathin CIGSe, which further induces high-parasitic absorption in the Mo layer, especially in the long-wavelength range. [18] On the one hand, various light-trapping strategies were developed to redirect and localize the light in the absorber, like nanoparticles (NPs) and reflective back mirrors. [19][20][21][22] On the other hand, if the ultrathin CIGSe was fabricated on a transparent back contact, the ultrathin CIGSe SCs become semitransparent, and the unabsorbed part of the light can be utilized in other ways. [9,13,23,24] Furthermore, semitransparent SCs have abundant application scenarios, for example, building-integrated PV, agrivoltaics, and vehicle-integrated PV. In addition, it is compatible with laser scribing in module fabrication. [25,26] Furthermore, bifacial SCs can exploit back-reflected light and thus enhance the efficiency. Given the earlier considerations, this work aims at improving the bifacial PV performance of bifacial semitransparent ultrathin CIGSe SCs (BSTUT CIGSe SCs) via SiO 2 -NP light trapping.

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Bifacial semi-transparent ultra-thin Cu(In,Ga)Se2 solar cells on ITO substrate: How ITO thickness and Na doping influence the performance

Cited by 16 publications

References 40 publications

Characterization of the Stability of Indium Tin Oxide and Functional Layers for Semitransparent Back‐Contact Applications on Cu(in,Ga)Se₂Solar Cells

Characterization of the Stability of Indium Tin Oxide and Functional Layers for Semitransparent Back‐Contact Applications on Cu(in,Ga)Se₂Solar Cells

Wide‐Gap Chalcopyrite Solar Cells with Indium Oxide–Based Transparent Back Contacts

Beyond Light‐Trapping Benefits: The Effect of SiO₂ Nanoparticles in Bifacial Semitransparent Ultrathin Cu(In,Ga)Se₂ Solar Cells

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Bifacial semi-transparent ultra-thin Cu(In,Ga)Se2 solar cells on ITO substrate: How ITO thickness and Na doping influence the performance

Cited by 16 publications

References 40 publications

Characterization of the Stability of Indium Tin Oxide and Functional Layers for Semitransparent Back‐Contact Applications on Cu(in,Ga)Se2Solar Cells

Characterization of the Stability of Indium Tin Oxide and Functional Layers for Semitransparent Back‐Contact Applications on Cu(in,Ga)Se2Solar Cells

Wide‐Gap Chalcopyrite Solar Cells with Indium Oxide–Based Transparent Back Contacts

Beyond Light‐Trapping Benefits: The Effect of SiO2 Nanoparticles in Bifacial Semitransparent Ultrathin Cu(In,Ga)Se2 Solar Cells

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Characterization of the Stability of Indium Tin Oxide and Functional Layers for Semitransparent Back‐Contact Applications on Cu(in,Ga)Se₂Solar Cells

Characterization of the Stability of Indium Tin Oxide and Functional Layers for Semitransparent Back‐Contact Applications on Cu(in,Ga)Se₂Solar Cells

Beyond Light‐Trapping Benefits: The Effect of SiO₂ Nanoparticles in Bifacial Semitransparent Ultrathin Cu(In,Ga)Se₂ Solar Cells