Efficiency boost of bifacial Cu(In,Ga)Se2 thin-film solar cells for flexible and tandem applications with silver-assisted low-temperature process

Yang, Shih‐Chi; Lin, Tzu-Chun; Ochoa, Mario; Lai, Huagui; Kothandaraman, Radha K.; Fu, Fan; Tiwari, Ayodhya N.; Carron, Romain

doi:10.1038/s41560-022-01157-9

Cited by 55 publications

(59 citation statements)

References 55 publications

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“…Figure 1c,d present scanning electron microscopy (SEM) images of the corresponding solar cells. Similar to lowgap chalcopyrite films, [27] the CuGaSe 2 grain size increases when Ag is added as a precursor, in line with earlier findings. [55] This could potentially explain (in parts) the better carrier collection.…”

Section: Effects Of Absorber Stoichiometry Growth Temperature and Sil...supporting

confidence: 89%

“…It was shown that already small amounts of silver, added in the form of a thin precursor layer, can lead to a substantial performance boost in low-gap chalcopyrite solar cells. [27,54,58,59] Thus, in a first experiment, only copper, gallium, and selenium were coevaporated on Mo-coated glass substrates with (labeled "pre-Ag") or without a 10 nm-thick Ag precursor layer to produce (A)CGS solar cells. The application of the Ag precursor led to a rather low AAC of about 0.02 in the final absorber film.…”

Section: Effects Of Absorber Stoichiometry Growth Temperature and Sil...mentioning

confidence: 99%

“…[23][24][25][26] Recently, research on the topic of TBCs has intensified and significant progress was observed, lifting the efficiency (η) of chalcopyrite solar cells with TBCs close to the level of those with standard Mo back contacts. [27][28][29][30][31][32][33] Thus, further improvements may be expected in the near future.…”

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confidence: 99%

“…[52] This allows to significantly reduce the process temperature and thereby increasing the performance of solar cells with heat-sensitive polyimide substrates [53] and transparent back contacts. [27,54] It may be speculated that the larger grain size generally leads to a longer minority carrier diffusion length (L n ) when silver is incorporated. However, up to now, Ag alloying did not result in a significant improvement for pure CuGaSe 2 solar cells.…”

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Silver Alloying in Highly Efficient CuGaSe₂ Solar Cells with Different Buffer Layers

et al. 2023

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The chalcopyrite semiconductor CuGaSe 2 exhibits a bandgap energy (E G ) of 1.6-1.7 eV [1][2][3] and is thus a promising absorber material for top solar cells in two-junction tandem devices. [4,5] However, the bulk quality of CuGaSe 2 is comparatively poor, [6,7] with a low electron lifetime resulting from a high Shockley-Read-Hall (SRH) recombination rate. Different origins, such as energetically deep defects (e.g., via Ga Cu ), a high density of defects, and/or detrimental, Cu-rich grain boundaries, are discussed. [8][9][10][11][12][13][14][15][16] In addition to losses directly related to the CuGaSe 2 layer itself, front interface recombination is supposed to be pronounced when a standard CdS buffer is used. This is due to a negative conduction band offset (CBO) at the CdS/CuGaSe 2 interface (ΔE C %À0.35 eV), leading to a very minor (or absent) type inversion and a high recombination rate at the interface. [17][18][19] The highest efficiencies of CuGaSe 2 solar cells reported so far are 11.9% for a sample with a (Zn 1Ày ,Sn y )O z (ZTO) buffer layer (our lab, noncertified) [2] and 11.0% with a standard CdS buffer layer (certified). [20] The corresponding photovoltaic parameters are open-circuit voltages (V OC ) of 1.017 and 0.901 V, short-circuit current densities ( J SC ) of 17.5 and 17.1 mA cm À2 , and fill factors (FF) of 67.0 and 71.3%, respectively. Obviously, the main improvement when exchanging CdS by an alternative ZTO buffer layer is the higher V OC , resulting from a reduced (or canceled out) interface recombination, as a negative CBO can be avoided when using ZTO. [21,22] It has to be mentioned that in order to use these wide-gap devices in a tandem configuration, a transparent back contact (TBC) needs to be incorporated. So far, the highest efficiencies of CuGaSe 2 solar cells on TBCs are much lower, at about 5%. [23][24][25][26] Recently, research on the topic of TBCs has intensified and significant progress was observed, lifting the efficiency (η) of chalcopyrite solar cells with TBCs close to the level of those with standard Mo back contacts. [27][28][29][30][31][32][33] Thus, further improvements may be expected in the near future.The best V OC values for CdS-buffered samples are achieved after a postannealing at 200 °C, reaching 971 mV for a polycrystalline [34] and 946 mV for a single-crystal absorber. [35] However, usually the postannealing results in a decrease in FF and the best V OC values for a sample without postannealing are about 920 mV [20,36] or 960 mV when a Cu-deficient surface layer was deliberately introduced and the CdS thickness increased. [37] In our lab, running a three-stage deposition process at a maximum temperature of 550 °C, the reported V OC values for CuGaSe 2 cells with CdS buffer layers are typically in the range of 730-830 mV. [2,38,39] Differences in device parameters between research groups are explainable by details in the sample processing, such as the temperature, [2] metal evaporation profiles, [40] and Se flux [20] during absorber deposition, variations in t...

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Section: Effects Of Absorber Stoichiometry Growth Temperature and Sil...supporting

confidence: 89%

Section: Effects Of Absorber Stoichiometry Growth Temperature and Sil...mentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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Silver Alloying in Highly Efficient CuGaSe₂ Solar Cells with Different Buffer Layers

et al. 2023

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“…This is primarily due to the potential for low fabrication costs and tunable bandgaps. [6][7][8] Indeed, research on the fabrication of Si/perovskite tandem solar cell technology has increased exponentially. [9][10][11][12] Within a short time, the power conversion efficiency (PCE) of 2-terminal (2T) Si/perovskite tandem solar cells has evolved from <20% to >30%, [10] even in large-area devices.…”

Section: Introductionmentioning

confidence: 99%

Stable and Efficient Large‐Area 4T Si/perovskite Tandem Photovoltaics with Sputtered Transparent Contact

et al. 2023

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Si-perovskite tandem photovoltaic devices in the four-terminal (4T) configuration could proffer a solution to the problems associated with the stability gap between the component perovskite and Si devices. The fabrication of NIR-transparent perovskite solar cells (PSCs) with the stable triple cation perovskite as the photoabsorber and subsequent integration with a Si solar cell in a 4T tandem device is reported. The critical development of the sputtered top transparent conducting electrode (TCE) layer and oxide buffer layer at room temperature (25 °C) leads to reproducible, highly efficient NIR-transparent PSCs of both small area (0.175 cm 2 ) with power conversion efficiency (PCE) of 17.1% and large area (0.805 cm 2 ) with PCE of 16.0%. Electrically disparate, optically coupled 4T tandem devices of the optimized PSCs with commercial monocrystalline PERC Si solar cells exhibit greater than 26% PCE. In addition to enabling industrycompatible TCE-based low-cost Si/perovskite tandem photovoltaics, this study could also be the gateway for the potential use in niche applications like building integrated photovoltaics.

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Rear Interface Engineering in Solution‐Processed Submicron Cu(In,Ga)(S,Se)₂ Solar Cells on Transparent Sn:In₂O₃ Back Contact

Gao,

Yin,

Schmid

2023

Adv Materials Inter

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The parasitic absorption in Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells emerging from the Mo back contact can be significantly reduced by replacing it with tin‐doped indium oxide (ITO). Commonly, an undesirable GaOx layer forms at the CIGSSe/ITO interface during the high‐temperature fabrication process, which has a detrimental effect on photo‐carrier extraction. Here, a Cu‐In‐TU‐DMF (TU: thiourea, DMF: N, N‐Dimethylformamide) intermediate layer for modification of the CIGSSe/ITO interface, which improves the efficiency of submicron CIGSSe solar cells significantly, is reported about. The reference submicron CIGSSe solar cells exhibit inferior performance (2.4% efficiency) and a large open circuit voltage deficit (Voc,def = 815.9 mV) due to a high barrier at the CIGSSe/ITO interface. At the modified rear interface, the recombination is reduced and hence carrier transport and collection are obviously improved. The efficiency of submicron CIGSSe solar cells on ITO with rear interface modification achieves 7.9% with an open circuit voltage of 565.8 mV, a short circuit current density of 23.4 mA cm−2, and a fill factor of 59.5%, as well as a Voc,def of 589.2 mV.

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Efficiency boost of bifacial Cu(In,Ga)Se2 thin-film solar cells for flexible and tandem applications with silver-assisted low-temperature process

Cited by 55 publications

References 55 publications

Silver Alloying in Highly Efficient CuGaSe₂ Solar Cells with Different Buffer Layers

Silver Alloying in Highly Efficient CuGaSe₂ Solar Cells with Different Buffer Layers

Stable and Efficient Large‐Area 4T Si/perovskite Tandem Photovoltaics with Sputtered Transparent Contact

Rear Interface Engineering in Solution‐Processed Submicron Cu(In,Ga)(S,Se)₂ Solar Cells on Transparent Sn:In₂O₃ Back Contact

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Efficiency boost of bifacial Cu(In,Ga)Se2 thin-film solar cells for flexible and tandem applications with silver-assisted low-temperature process

Cited by 55 publications

References 55 publications

Silver Alloying in Highly Efficient CuGaSe2 Solar Cells with Different Buffer Layers

Silver Alloying in Highly Efficient CuGaSe2 Solar Cells with Different Buffer Layers

Stable and Efficient Large‐Area 4T Si/perovskite Tandem Photovoltaics with Sputtered Transparent Contact

Rear Interface Engineering in Solution‐Processed Submicron Cu(In,Ga)(S,Se)2 Solar Cells on Transparent Sn:In2O3 Back Contact

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About

Silver Alloying in Highly Efficient CuGaSe₂ Solar Cells with Different Buffer Layers

Silver Alloying in Highly Efficient CuGaSe₂ Solar Cells with Different Buffer Layers

Rear Interface Engineering in Solution‐Processed Submicron Cu(In,Ga)(S,Se)₂ Solar Cells on Transparent Sn:In₂O₃ Back Contact