Peeled-off flexible Cu(In,Ga)Se2 solar cells and Na diffusion effects on cell performances

Sadono, Adiyudha; Ogihara, Tomohiro; Hino, Masashi; Yamamoto, Kenji; Yamada, Akira

doi:10.1007/s13391-016-4012-1

Cited by 12 publications

(9 citation statements)

References 17 publications

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“…As an example, band gap grading design, through Ga-content control, have had a significant impact [11,12], and numerous theoretical studies in band grading designs are still underway [13][14][15]. The additional step of absorber layer's post-deposition treatment (PDT) using alkali [16,17] have also been known to have a positive impact on the CIGSe 2 solar cell's performance. In addition, the importance of the pn-junction interface between the buffer layer and the absorber layer in non-radiative recombination was identified empirically [18][19][20] and further validated through a numerical study [21].…”

Section: Introductionmentioning

confidence: 99%

Benefits of Low Electron-Affinity Material as the N-Type Layer for Cu(In,Ga)S2 Solar Cell

Egyna¹,

Nakada²,

Yamada³

2021

Energies

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Despite the potential in single- and multi-junction solar cells application, research into the wide band gap CuIn1−xGax(Se1−ySy)2 or CIG(SSe)2 solar cell material, with Eg≥1.5eV, has yet to be extensively performed to date. In this work, we conducted a numerical study into the role of the n-type layers in CIG(SSe)2 heterojunction solar cells, specifically concerning the maximum open-circuit voltage of the devices. In the first part of the study, we derived a new ideal open-circuit voltage equation for a thin-film heterojunction solar cell by taking into account the current contribution from the depletion region. The accuracy of the new equation was validated through a simulation model in the second part of the study. Another simulation model was also used to clarify the design rules of the n-type layer in a wide band gap CIG(SSe)2 solar cell. Our work stressed the importance of a positive conduction band offset on the n-/p-type interface, through the use of a low electron affinity n-type material for a solar cell with a high open-circuit voltage . Through a precise selection of the window layer material, a buffer-free CIG(SSe)2 design is sufficient to fulfill such conditions. We also proposed the specific roles of the n-type layer, i.e., as a passivation layer and selective electron contact, in the operation of CIGS2 solar cells.

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Section: Introductionmentioning

confidence: 99%

Benefits of Low Electron-Affinity Material as the N-Type Layer for Cu(In,Ga)S2 Solar Cell

Egyna¹,

Nakada²,

Yamada³

2021

Energies

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“…Application of post-deposition treatments (PDTs) with alkali fluoride (KF, RbF, or CsF), beyond the conventional choice of Na, has been proven to be essential in the recent performance improvements of CIGS solar cells. , Numerous studies have reported on the role of the most common element for these alkali treatments, namely, Na. The studies have revealed that Na reduces donor-like deep-level defects in the bulk, reinforcing p-type characteristics of the CIGS absorber − and passivates grain boundaries (GBs) . Controllable incorporation of Na after the growth of CIGS via PDT, that is, evaporation of NaF onto the CIGS film, led to the highest power conversion efficiency of CIGS solar cells among those with an external supply of Na (other than diffusion from soda-lime glass) .…”

Section: Introductionmentioning

confidence: 99%

Passivation of Deep-Level Defects by Cesium Fluoride Post-Deposition Treatment for Improved Device Performance of Cu(In,Ga)Se₂ Solar Cells

Lee

Jang

Nam

et al. 2019

ACS Appl. Mater. Interfaces

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Heavy-alkali post-deposition treatments (PDTs) utilizing Cs or Rb has become an indispensable step in producing high-performance Cu(In,Ga)Se 2 (CIGS) solar cells. However, full understanding of the mechanism behind the improvements of device performance by heavyalkali treatments, particularly in terms of potential modification of defect characteristics, has not been reached yet. Here, we present an extensive study on the effects of CsF-PDT on material properties of CIGS absorbers and the performance of the final solar devices. Incorporation of an optimized concentration of Cs into CIGS resulted in a significant improvement of the device efficiency from 15.9 to 18.4% mainly due to an increase in the open-circuit voltage by 50 mV. Strong segregation of Cs at the front and rear interfaces as well as along grain boundaries of CIGS was observed via high-resolution chemical analysis such as atomic probe tomography. The study of defect chemistry using photoluminescence and capacitance-based measurements revealed that both deep-level donor-like defects such as V Se and In Cu and deep-level acceptor-like defects such as V In or Cu In are passivated by CsF-PDT, which contribute to an increased hole concentration. Additionally, it was found that CsF-PDT induces a slight change in the energetics of V Cu , the most dominant point defect that is responsible for the p-type conductivity of CIGS.

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“…The resistance at GBs and grain interior (GI) was almost the same in Cu(In,Ga) 3 Se 5 , while GBs showed lower resistance than GI in CIGS. It has been widely known that Na derived from SLG substrate passivates defects and increases carrier concentration in CIGS . Therefore, the low resistance at GBs of CIGS observed in Figure A is attributed to Na.…”

Section: Resultsmentioning

confidence: 93%

“…On the contrary, high Na contents of 2.0 and 2.1 at% at points 8 and 9, respectively, were detected, although there were hardly Cd atoms. This indicates that Na atoms, which lead to increment of carrier concentration in CIGS, were strongly affected at points 8 and 9 because Cd diffusion did not reach up to deep position at 600 and 900 nm from the CdS/CIGS interface. As a result, carrier concentration at points 8 and 9 had higher values of 1.3 × 10 16 and 1.2 × 10 16 cm −3 than that of 6.2 × 10 14 cm −3 at point 7.…”

Section: Resultsmentioning

confidence: 99%

Effect of Cu‐deficient layer formation in Cu(In,Ga)Se₂ solar‐cell performance

Nishimura

Toki

Sugiura

et al. 2017

Progress in Photovoltaics

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Cu-deficient layer (CDL) on Cu(In,Ga)Se 2 (CIGS) promotes Cd diffusion from CdS buffer layer and forms a valence band offset (ΔE V ) between CDL and CIGS. We quantitively demonstrate the effects of CDL formation on the performance of CIGS solar cells through experiments and theoretical simulation. To investigate the effects of Cd diffusion and ΔE V by CDL, theoretical analysis was carried out for a CIGS solar cell with a surface layer which simulated the CDL at CdS/CIGS interface. It was revealed that when electron concentration in n-type surface layer is higher than the absolute carrier concentration in CIGS absorber (N D > |N A, CIGS |), open-circuit voltage and fill factor are improved. Additionally, ΔE V ≥ 0.15 eV leads to the highest open-circuit voltage by suppression of interfacial recombination. Transmission electron microscope energy dispersive X-ray spectrometry and scanning spreading resistance microscopy were employed for the same cross section of a CIGS solar cell fabricated by three-stage process. Despite CDL with Cu/(Ga + In) of 0.31 formed on the surface had high Cd contents of 3.4 at%, its carrier concentration of 4.8 × 10 10 cm −3 was lower than that of 10 14 -10 16 cm −3 in grain interior owing to insufficient activation of Cd atoms. These results indicate the effectiveness of ΔE V formation by introducing CDL with low Cu/(Ga + In) of 0.31 to boost CIGS solar cell performance and difficulty in realizing N D > |N A, CIGS | by surface Cd doping.

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Peeled-off flexible Cu(In,Ga)Se2 solar cells and Na diffusion effects on cell performances

Cited by 12 publications

References 17 publications

Benefits of Low Electron-Affinity Material as the N-Type Layer for Cu(In,Ga)S2 Solar Cell

Benefits of Low Electron-Affinity Material as the N-Type Layer for Cu(In,Ga)S2 Solar Cell

Passivation of Deep-Level Defects by Cesium Fluoride Post-Deposition Treatment for Improved Device Performance of Cu(In,Ga)Se₂ Solar Cells

Effect of Cu‐deficient layer formation in Cu(In,Ga)Se₂ solar‐cell performance

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Peeled-off flexible Cu(In,Ga)Se2 solar cells and Na diffusion effects on cell performances

Cited by 12 publications

References 17 publications

Benefits of Low Electron-Affinity Material as the N-Type Layer for Cu(In,Ga)S2 Solar Cell

Benefits of Low Electron-Affinity Material as the N-Type Layer for Cu(In,Ga)S2 Solar Cell

Passivation of Deep-Level Defects by Cesium Fluoride Post-Deposition Treatment for Improved Device Performance of Cu(In,Ga)Se2 Solar Cells

Effect of Cu‐deficient layer formation in Cu(In,Ga)Se2 solar‐cell performance

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Passivation of Deep-Level Defects by Cesium Fluoride Post-Deposition Treatment for Improved Device Performance of Cu(In,Ga)Se₂ Solar Cells

Effect of Cu‐deficient layer formation in Cu(In,Ga)Se₂ solar‐cell performance