Bifacial CIGS solar cells grown by Low Temperature Pulsed Electron Deposition

Mazzer, M.; Rampino, Stefano; Spaggiari, Giulia; Annoni, Filippo; Bersani, Danilo; Bissoli, F.; Bronzoni, Matteo; Calicchio, M.; Gombia, E.; Kingma, Aldo; Pattini, F.; Gilioli, E.

doi:10.1016/j.solmat.2016.10.048

Cited by 47 publications

(31 citation statements)

References 20 publications

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“…The “Ref” samples show an increasing collection probability with increasing wavelength at back side illumination. This is typically observed in EQE spectra if the diffusion length and/or the back contact recombination are limiting . With increasing IOH thickness, the absolute level increases by a similar value for all wavelengths (ie, generation depths).…”

Section: Resultsmentioning

confidence: 73%

Bifacial Cu(In,Ga)Se₂ solar cells using hydrogen‐doped In₂O₃ films as a transparent back contact

Keller

Chen

Riekehr

et al. 2018

Progress in Photovoltaics

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Hydrogen-doped In 2 O 3 (IOH) films are used as a transparent back contact in bifacial Cu(In,Ga)Se 2 (CIGS) solar cells. The effect of the IOH thickness and the impact of the sodium incorporation technique on the photovoltaic parameters are studied, and clear correlations are observed. It is shown that a loss in short circuit current density (J SC ) is the major limitation at back side illumination. The introduction of a thin Al 2 O 3 layer on top of the IOH significantly increases the collection efficiency (ϕ(x)) for electrons generated close to the back contact. In this way, the J SC loss can be mitigated to only~25% as compared with front side illumination. The Al 2 O 3 film potentially reduces the interface defect density or, alternatively, creates a field effect passivation. In addition, it prevents the excessive formation of Ga 2 O 3 at the CIGS/ IOH interface, which is found otherwise when a NaF layer is added before absorber deposition. Consequently, detrimental redistributions in Ga and In close to the back contact can be avoided. Finally, a bifacial CIGS solar cell with an efficiency (η) of η = 11.0% at front and η = 6.0% at back side illumination could be processed. The large potential for further improvements is discussed.

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Section: Resultsmentioning

confidence: 73%

Bifacial Cu(In,Ga)Se₂ solar cells using hydrogen‐doped In₂O₃ films as a transparent back contact

Keller

Chen

Riekehr

et al. 2018

Progress in Photovoltaics

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“…It is mainly because thermal energy is needed for Cu diffusion, as well as to promote grain growth and annihilate defects. [ 4–6 ] Although single‐stage low‐temperature pulsed electron deposition (LTPED) can yield the efficiencies up to 17.0% at 250 °C, [ 7,8 ] this technique presents scale‐up challenges and technical issues such as the presence of micrometer‐sized particle. [ 9 ] A simpler method offering high performance and a better potential for transferring from laboratory to manufacturing is, therefore, needed.…”

Section: Introductionmentioning

confidence: 99%

Silver‐Promoted High‐Performance (Ag,Cu)(In,Ga)Se₂ Thin‐Film Solar Cells Grown at Very Low Temperature

et al. 2021

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Achieving high power conversion efficiencies with Cu(In,Ga)Se2 (CIGS) solar cells grown at low temperature is challenging because of insufficient thermal energy for grain growth and defect annihilation, resulting in poor crystallinity, higher defect concentration, and degraded device performance. Herein, the possibilities for high‐performing devices produced at very low temperatures (≤450 °C) are explored. By alloying CIGS with Ag by the precursor layer method, (Ag,Cu)(In,Ga)Se2 (ACIGS) solar cells grown at about 450 °C reach an efficiency of 20.1%. Only a small efficiency degradation (0.5% and 1.6% absolute) is observed for ACIGS absorbers deposited at 60 and 110 °C lower substrate temperature. CIGS devices exhibit a stronger efficiency degradation, driven by a decrease in the open‐circuit voltage (VOC). The root cause of the VOC difference between ACIGS and CIGS devices is investigated by advanced characterization techniques, which show improved morphology, reduced tail states, and higher doping density in ACIGS absorbers. The proposed approach offers several benefits in view of depositions on temperature‐sensitive substrates. Increased Cu diffusion promoted by Ag allows end‐point detection in the three‐stage process at the substrate temperatures below 300 °C. The modified process requires minimal modification of existing processes and equipment and shows the potential for the use of different flexible substrates and device architectures.

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“…A possible way to circumvent these deteriorations is to apply low‐temperature absorber deposition processes ( T < 500°C) to avoid the formation of Ga 2 O 3 and losses in lateral conductivity . However, most CIGS processes used for manufacturing of high‐efficiency devices and full‐scale modules use a high‐temperature stage today.…”

Section: Introductionmentioning

confidence: 99%

Using hydrogen‐doped In₂O₃ films as a transparent back contact in (Ag,Cu)(In,Ga)Se₂ solar cells

Keller

Nilsson

Aijaz

et al. 2018

Progress in Photovoltaics

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This study evaluates the potential of hydrogen-doped In 2 O 3 (IOH) as a transparent back contact material in (Ag y ,Cu 1-y )(In 1-x ,Ga x )Se 2 solar cells. It is found that the presence of Na promotes the creation of Ga 2 O 3 at the back contact during (Ag y ,Cu 1-y )(In 1-x ,Ga x )Se 2 growth. An excessive Ga 2 O 3 formation results in a Ga depletion, which extends deep into the absorber layer.Consequently, the beneficial back surface field is removed and a detrimental reversed electrical field establishes. However, for more moderate Ga 2 O 3 amounts (obtained with reduced Na supply), the back surface field can be preserved. Characterization of corresponding solar cells suggests the presence of an ohmic back contact, even at absorber deposition temperatures of 550°C. The best solar cell with an IOH back contact shows a fill factor of 74% and an efficiency contacts are further needed in bifacial devices, which can be semitransparent if desired (eg, for "solar windows"). The upper cells in a multijunction tandem structure need to be grown on TBCs as well to allow for light propagation to the bottom cell. An advantage of these approaches over a superstrate configuration is that the required buffer layer does not have to undergo the thermal stress during absorber formation. Up to now, there are no buffer materials found, which are chemically stable at high temperatures, which results in a significant efficiency drop compared to substrate-configured solar cells. 4,5 Nevertheless, there are some requirements to a TBC as well. After the thermal stress during absorber formation, it still needs to (1) create an ohmic contact to the absorber, (2) be highly transparent, and (3) exhibit a low sheet resistance (R SH ). In the case of CIGS-based solar cells, it also needs to exhibit a certain permeability for alkaline ions, if they are supposed to be supplied from the underlying glass substrate.In the past, different transparent conductive oxide (TCO) layers have been investigated as potential TBC materials for CIGS solar cells. In this study, we use (Ag,Cu)(In,Ga)Se 2 (ACIGS) as an absorber material, which is proven to result in large grain sizes 19 and highefficiency solar cells. 20,21 The silver was added intentionally, since V OC losses for higher absorber band gap energies are less pronounced in ACIGS compared to CIGS. 21 This is in particular interesting for top cells in a tandem configuration where the optimum band gap energy E G is about 1.6 eV (two junctions).It should be emphasized that this work is supposed to act as a first potential evaluation for IOH as a TBC. Hence, the cell structure was designed for maximized efficiencies at normal front side illumination, which means that the absorber layer is about 2 μm thick and has a band gap energy of about 1.2 eV. | MATERIALS AND METHODS | Sample fabrication and configurationsThe ACIGS solar cells investigated in this study were manufactured as a stack of soda lime glass (SLG)/back contact/ACIGS/CdS/i-ZnO/AZO.As a back contact either IOH or standard Mo (DC-sp...

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Bifacial CIGS solar cells grown by Low Temperature Pulsed Electron Deposition

Cited by 47 publications

References 20 publications

Bifacial Cu(In,Ga)Se₂ solar cells using hydrogen‐doped In₂O₃ films as a transparent back contact

Bifacial Cu(In,Ga)Se₂ solar cells using hydrogen‐doped In₂O₃ films as a transparent back contact

Silver‐Promoted High‐Performance (Ag,Cu)(In,Ga)Se₂ Thin‐Film Solar Cells Grown at Very Low Temperature

Using hydrogen‐doped In₂O₃ films as a transparent back contact in (Ag,Cu)(In,Ga)Se₂ solar cells

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Bifacial CIGS solar cells grown by Low Temperature Pulsed Electron Deposition

Cited by 47 publications

References 20 publications

Bifacial Cu(In,Ga)Se2 solar cells using hydrogen‐doped In2O3 films as a transparent back contact

Bifacial Cu(In,Ga)Se2 solar cells using hydrogen‐doped In2O3 films as a transparent back contact

Silver‐Promoted High‐Performance (Ag,Cu)(In,Ga)Se2 Thin‐Film Solar Cells Grown at Very Low Temperature

Using hydrogen‐doped In2O3 films as a transparent back contact in (Ag,Cu)(In,Ga)Se2 solar cells

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Product

Resources

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Bifacial Cu(In,Ga)Se₂ solar cells using hydrogen‐doped In₂O₃ films as a transparent back contact

Bifacial Cu(In,Ga)Se₂ solar cells using hydrogen‐doped In₂O₃ films as a transparent back contact

Silver‐Promoted High‐Performance (Ag,Cu)(In,Ga)Se₂ Thin‐Film Solar Cells Grown at Very Low Temperature

Using hydrogen‐doped In₂O₃ films as a transparent back contact in (Ag,Cu)(In,Ga)Se₂ solar cells