Sodium-doped molybdenum back contacts for flexible Cu(In,Ga)Se2 solar cells

Blösch, P.; Nishiwaki, Shiro; Chirilă, A.; Kranz, Lukas; Fella, C.M.; Pianezzi, Fabian; Adelhelm, C.; Franzke, Enrico; Buecheler, Stephan; Tiwari, Ayodhya N.

doi:10.1016/j.tsf.2012.10.080

Cited by 22 publications

(12 citation statements)

References 15 publications

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“…The targets are commonly prepared by mixing Mo with a certain percentage of sodium molybdate, with concentrations of Na that can vary from 2% to 15% [at] [105]. In two publications, Blosch et al [106,107] have stated that Na easily diffuses from internal interfaces of two MoNa layers possibly because Na moves through grain boundaries. In addition they also found that the microstructure of the MoNa layers strongly influence this diffusion, in accordance with several findings [57,108].…”

Section: Mona Back Contact Layermentioning

confidence: 99%

Incorporation of alkali metals in chalcogenide solar cells

Salomé

Rodríguez-Alvarez

Sadewasser

2015

Solar Energy Materials and Solar Cells

126

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Section: Mona Back Contact Layermentioning

confidence: 99%

Incorporation of alkali metals in chalcogenide solar cells

Salomé

Rodríguez-Alvarez

Sadewasser

2015

Solar Energy Materials and Solar Cells

126

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“…Alkaline metals incorporating in Cu(In, Ga)Se 2 (CIGSe) and Cu 2 ZnSnS 4 (CZTS) have experimentally shown significant improvement in photovoltaic efficiencies. As sodium treatment technology advances, such as postdeposition treatment, soda‐lime glass substrate, and Na in Mo back contacts, solar cells' efficiencies have risen to 22.6% for CIGS and 12.6% for CZTS . However, despite decades of investigations, the reason for success of sodium treatment is still a mystery.…”

Section: Introductionmentioning

confidence: 99%

Sodium Passivation of the Grain Boundaries in CuInSe₂ and Cu₂ZnSnS₄ for High‐Efficiency Solar Cells

Chengyan

et al. 2016

Advanced Energy Materials

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It is well known that sodium at grain boundaries (GBs) increases the photovoltaic efficiencies of CuInSe 2 and Cu 2 ZnSnS 4 significantly. However, the mechanism of how sodium influences the GBs is still unknown. Based on the recently proposed self-passivation rule, it is found that the dangling bonds in the GBs can completely be saturated through doping the Na, thus GB states are successfully passivated. It is shown that the Na can easily incorporate into the GB with very low formation energy. Although Cu can also passivate the GB states, it requires a copper rich condition which, however, suppresses the formation of copper vacancies in the bulk and thus decreases the concentration of hole carriers, so copper passivation is practically not as beneficial as sodium. The present work reveals the mechanism about how the Na enhances the photovoltaic performance through passivating the dangling bonds in the GBs of chalcogenide semiconductors, and sheds light on how to passivate dangling bonds in GBs with alterative processes.

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“…14 When CIGS solar cells are produced on SLG, Na diffuses during the absorber growth from the substrate through the Mo electrical back contact into the CIGS layer. To produce flexible CIGS solar cells on alkali-free substrates such as metal foils or polyimide, [15][16][17][18] various techniques for Na incorporation have been developed, e.g., from a Na doped Mo back contact, 15,19,20 by the deposition of a precursor layer, 21 by co-evaporation, 7,22 by a post deposition treatment (PDT), 6 or from an enamel coating of the substrate. 23 Up to now, Na is considered to be the most effective alkaline dopant to improve the device performance, although it was observed in several studies that K is also incorporated in CIGS layers grown on SLG.…”

Section: Introductionmentioning

confidence: 99%

Defect formation in Cu(In,Ga)Se2 thin films due to the presence of potassium during growth by low temperature co-evaporation process

Pianezzi

Reinhard

Chirilă

et al. 2013

Journal of Applied Physics

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Doping the Cu(In,Ga)Se 2 (CIGS) absorber layer with alkaline metals is necessary to process high efficiency solar cells. When growth of CIGS solar cells is performed on soda-lime glass (SLG), the alkaline elements naturally diffuse from the substrate into the absorber layer. On the other hand, when CIGS is grown on alkaline free substrates, the alkaline metals have to be added from another source. In the past, Na was believed to be the most important dopant of the alkaline elements, even though K was also observed to diffuse into CIGS from the SLG. Recently, the beneficial effect of a post deposition treatment with KF was pointed out and enabled the production of a 20.4% CIGS solar cell grown at low substrate temperature (<500 C). However, possible negative effects of the presence or addition of the alkaline impurities during the low temperature growth process were observed for Na, but were not investigated for K so far. In this study, we investigate in detail the role of K on the defect formation in CIGS layers deposited at low temperature on alkaline free polyimide with intentional addition of K during selected time intervals of the CIGS layer growth. By means of admittance spectroscopy and deep level transient spectroscopy, we identify a deep minority carrier trap at around 280 meV below the conduction band E C in CIGS layers grown with K. Its influence on recombination and minority carrier lifetime in the absorber layer is investigated with external quantum efficiency measurements and time-resolved photoluminescence. Furthermore, to support the experimental findings device simulations were performed using the software SCAPS. V

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Sodium-doped molybdenum back contacts for flexible Cu(In,Ga)Se2 solar cells

Cited by 22 publications

References 15 publications

Incorporation of alkali metals in chalcogenide solar cells

Incorporation of alkali metals in chalcogenide solar cells

Sodium Passivation of the Grain Boundaries in CuInSe₂ and Cu₂ZnSnS₄ for High‐Efficiency Solar Cells

Defect formation in Cu(In,Ga)Se2 thin films due to the presence of potassium during growth by low temperature co-evaporation process

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Sodium-doped molybdenum back contacts for flexible Cu(In,Ga)Se2 solar cells

Cited by 22 publications

References 15 publications

Incorporation of alkali metals in chalcogenide solar cells

Incorporation of alkali metals in chalcogenide solar cells

Sodium Passivation of the Grain Boundaries in CuInSe2 and Cu2ZnSnS4 for High‐Efficiency Solar Cells

Defect formation in Cu(In,Ga)Se2 thin films due to the presence of potassium during growth by low temperature co-evaporation process

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Sodium Passivation of the Grain Boundaries in CuInSe₂ and Cu₂ZnSnS₄ for High‐Efficiency Solar Cells