The influence of sodium on the molybdenum/Cu(In,Ga)Se2 interface recombination velocity, determined by time resolved photoluminescence

Jarzembowski, Enrico; Syrowatka, Frank; Kaufmann, Kai; Fränzel, Wolfgang; Hölscher, Torsten; Scheer, Roland

doi:10.1063/1.4928187

Cited by 17 publications

(14 citation statements)

References 25 publications

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“…However, the effect of the MSSe layer formed at the back electrode on the PCE is still argued. [35][36][37] In order to understand mechanism of effect of selenization temperature and time on the PCE, three solar cells with structure of SLG/Mo/CZTSSe/CdS/i-ZnO/indium tin oxide (ITO)/Al grid were prepared by using the CZTSSe absorber layers prepared at 530 °C in the selenization time of 5, 15 and 30 min, respectively, and were investigated by measurement of their current density(J)-voltage(V) curves under AM 1.5G illumination. Fig.…”

Section: / 34mentioning

confidence: 97%

“…preventing phase segregation, and increment of grain size and compactness of the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 4/ 34 properties of CZTSSe-based solar cell is still argued up to now. [35][36][37] In this work, we prepare CZTSSe films by annealing CZTS precursor films deposited on Mo coated glass under selenium vapor; and systematically investigate the changes of structure and crystal quality of the CZTSSe films and CZTSSe/Mo interfaces. Our work demonstrates that the MSSe layer has smaller effect on the R s , but it has larger influence on the G sh , n and J 0 .…”

Section: Introductionmentioning

confidence: 99%

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Influencing Mechanism of the Selenization Temperature and Time on the Power Conversion Efficiency of Cu₂ZnSn(S,Se)₄-Based Solar Cells

Xiao

et al. 2016

ACS Appl. Mater. Interfaces

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Cu2ZnSn(S,Se)4 (CZTSSe) films were deposited on the Mo-coated glass substrates, and the CZTSSe-based solar cells were successfully fabricated by a facile solution method and postselenization technique. The influencing mechanisms of the selenization temperature and time on the power conversion efficiency (PCE), short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) of the solar cell are systematically investigated by studying the change of the shunt conductance (Gsh), series resistance (Rs), diode ideal factor (n), and reversion saturation current density (J0) with structure and crystal quality of the CZTSSe film and CZTSSe/Mo interface selenized at various temperatures and times. It is found that a Mo(S1-x,Sex)2 (MSSe) layer with hexagonal structure exists at the CZTSSe/Mo interface at the temperature of 500 °C, and its thickness increases with increasing selenization temperature and time. The MSSe has a smaller effect on the Rs, but it has a larger influence on the Gsh, n, and J0. The PCE, Voc, and FF change dominantly with Gsh, n, and J0, while Jsc changes with Rs and Gsh, but not Rs. These results suggest that the effect of the selenization temperature and time on the PCE is dominantly contributed to the change of the CZTSSe/CdS p-n junction and CZTSSe/MSSe interface induced by variation of the quality of the CZTSSe film and thickness of MSSe in the selenization process. By optimizing the selenization temperature and time, the highest PCE of 7.48% is obtained.

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Section: / 34mentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Influencing Mechanism of the Selenization Temperature and Time on the Power Conversion Efficiency of Cu₂ZnSn(S,Se)₄-Based Solar Cells

Xiao

et al. 2016

ACS Appl. Mater. Interfaces

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“…However, cells with too little Sodium also exhibit poor performance possibly also due to high interface recombination. It has been surmised that Sodium has an ambiguous role for interface recombination and can also lead to passivation of the front surface 47 and back contact 48 . In effect, there is an optimum NaF‐PDT thickness.…”

Section: Discussionmentioning

confidence: 99%

Effect of Na‐PDT and KF‐PDT on the photovoltaic performance of wide bandgap Cu (In,Ga)Se2 solar cells

Zahedi‐Azad

Maiberg

Scheer

2020

Progress in Photovoltaics

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Cu (In,Ga)Se 2 solar cells exhibit higher efficiencies if an appropriate Ga gradient is introduced and if the absorber is doped with sodium (Na) plus a heavier alkali atom such as potassium. However, a Gallium gradient in the presence of Na is challenging because sodium impedes the interdiffusion of elements and influences the gradient. In this contribution, we show that the presence of sodium during growth with the combination of high Ga concentration creates a pronounced gradient that is detrimental for carrier collection. One solution is to avoid Na abundance during absorber growth but to add it to the grown absorber layer via a postdeposition treatment. We investigate the effect of different Na incorporation methods simultaneously with KF-PDT on wide band gap CIGSe absorbers. By preparation on alkali-free substrates and application of alkalis (NaF and KF) onto a grown CIGSe layer, we show by smoothening of the Gallium gradient a large improvement in the solar cell performance from 4% to 8%. Another way to optimize the gradient in the presence of Na is the modification of the three-stage method. This yields the best efficiency of 10% in our laboratory at an integral GGI of 0.8. By means of temperature-dependent JV measurements, we show that the additional postdeposition of KF induces a barrier for the diode current. We conclude that KF-PDT induces a new thin layer at the CIGSe surface that has a lower valence band edge relative to the CIGSe bulk and is responsible for the double-diode behavior. This barrier can also explain the V oc (T) saturation at low temperature.

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“…[ 1–4 ] However, this requires a very low back contact recombination velocity and advanced optical light management. The standard molybdenum back contact is generally attributed with a high recombination velocity [ 5–7 ] and has a poor optical reflectivity. [ 8 ] In ref.…”

Section: Introductionmentioning

confidence: 99%

Ultrathin CIGSe Solar Cells with Integrated Structured Back Reflector

et al. 2020

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Reducing the thickness of thin-film solar cells reduces the total cost of ownership of solar module production. Theoretically, a 500 nm Cu(In,Ga)Se 2 (CIGSe) solar cell allows more than 20% efficiency. [1-4] However, this requires a very low back contact recombination velocity and advanced optical light management. The standard molybdenum back contact is generally attributed with a high recombination velocity [5-7] and has a poor optical reflectivity. [8] In ref. [9], a ZrN layer on top of molybdenum having a reflectivity of 60% was used with the result of increased quantum efficiency at long wavelengths. An even higher reflectivity and higher gain in photocurrent could be achieved by an Au back reflector applied by post-deposition recontacting after removing the Mo layer. [10] In addition to cost aspects, Au is not suitable for direct deposition of CIGSe thin films at high temperatures due to the chemical reactivity with the chalcogen species during CIGSe deposition. The latter is also true for other highly reflective metals such as Ag, Cu, and Al. [11] Instead, these metals have to be encapsulated by a transparent and conductive diffusion barrier layer. Bissig et al. investigated an Al/InZnO back contact for solar cells with an absorber thickness of 2.1 μm and were able to increase the short-circuit density up to 1.4 mA cm À2 compared with a sample with Mo back contact, despite the relatively high absorber thickness. [12] According to former work on transparent back contacts, the transparent conductor indium-tin-oxide (ITO) is a good candidate as a transparent back contact [13] and as a diffusion barrier. [14] Recently, ref. [15] showed an experimental gain in short-circuit current density of 4.9 mA cm À2 in a structure Mo/Ag/ITO/0.5 μm CIGSe with respect to the reference structure of Mo/0.5 μm CIGSe. Al/ITO-based solar cells can be prepared up to at least 600 C without Al diffusion inside the absorber while providing high reflectivity at long optical wavelengths. [16] This raises the question of the electronic properties of the ITO/CIGSe contact. Keller et al. investigated 650 nm CIGSe bifacial solar cells with a hydrogen-doped In 2 O 3 back contact [17] and quantified the back-contact recombination velocity to the range of 10 7 cm s À1. This value dropped by application of an Al 2 O 3 þ NaF precursor layer stack as confirmed by a strongly increased rear-side external quantum efficiency (EQE) at short wavelengths. Unfortunately, the 5 nm Al 2 O 3 conformal layer reduces the fill factor (FF). [17] Although a flat optical reflector enhances the long-wavelength EQE upon front-side illumination to some extent, light scattering is required in addition to approach the Yablonovitch limit. [18] Yin et al. used ITO as transparent back contact and applied both dielectric SiO 2 nanoparticles on top of ITO and an external Ag mirror behind the substrate glass achieving a very high short-circuit current density of 32.4 mA cm À2 with an absorber thickness of only 390 nm. [19] This was an important step toward a structured an...

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The influence of sodium on the molybdenum/Cu(In,Ga)Se2 interface recombination velocity, determined by time resolved photoluminescence

Cited by 17 publications

References 25 publications

Influencing Mechanism of the Selenization Temperature and Time on the Power Conversion Efficiency of Cu₂ZnSn(S,Se)₄-Based Solar Cells

Influencing Mechanism of the Selenization Temperature and Time on the Power Conversion Efficiency of Cu₂ZnSn(S,Se)₄-Based Solar Cells

Effect of Na‐PDT and KF‐PDT on the photovoltaic performance of wide bandgap Cu (In,Ga)Se2 solar cells

Ultrathin CIGSe Solar Cells with Integrated Structured Back Reflector

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The influence of sodium on the molybdenum/Cu(In,Ga)Se2 interface recombination velocity, determined by time resolved photoluminescence

Cited by 17 publications

References 25 publications

Influencing Mechanism of the Selenization Temperature and Time on the Power Conversion Efficiency of Cu2ZnSn(S,Se)4-Based Solar Cells

Influencing Mechanism of the Selenization Temperature and Time on the Power Conversion Efficiency of Cu2ZnSn(S,Se)4-Based Solar Cells

Effect of Na‐PDT and KF‐PDT on the photovoltaic performance of wide bandgap Cu (In,Ga)Se2 solar cells

Ultrathin CIGSe Solar Cells with Integrated Structured Back Reflector

Contact Info

Product

Resources

About

Influencing Mechanism of the Selenization Temperature and Time on the Power Conversion Efficiency of Cu₂ZnSn(S,Se)₄-Based Solar Cells

Influencing Mechanism of the Selenization Temperature and Time on the Power Conversion Efficiency of Cu₂ZnSn(S,Se)₄-Based Solar Cells