Coevaporated KInSe<sub>2</sub>: A Fast Alternative to KF Postdeposition Treatment in High-Efficiency Cu(In,Ga)Se<sub>2</sub>Thin Film Solar Cells

Lepetit, Thomas; Harel, Sylvie; Arzel, Ludovic; Ouvrard, G.; Barreau, Nicolas

doi:10.1109/jphotov.2016.2589365

Cited by 48 publications

(60 citation statements)

References 15 publications

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“…[25] It was found that similar to a KF PDT, a surface layer forms. [5][6][7][8][9]26,30] Additionally, as presented here for a RbF PDT, with the introduction of a KF PDT, a blocking of the diode current was observed. [15] Recently, Malitckaya et al calculated the bandgap energies of AlkInSe 2 (Alk = Li, Na, K, Rb, Cs) secondary phases, which are expected to segregate on the surface of the CIGS absorber for K, Rb, and Cs.…”

Section: Discussionsupporting

confidence: 67%

See 1 more Smart Citation

Injection Current Barrier Formation for RbF Postdeposition‐Treated Cu(In,Ga)Se₂‐Based Solar Cells

Weiss

Nishiwaki

Bissig

et al. 2017

Adv Materials Inter

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Among the thin‐film solar cell technologies, Cu(In,Ga)Se2‐based solar cells demonstrate the highest efficiencies, where the recent boost in efficiency is triggered by a KF postdeposition treatment (PDT). In this contribution, Cu(In,Ga)Se2‐based solar cells are fabricated using RbF PDTs after absorber layer growth with varying substrate and RbF source temperature. The electronic charge transport properties of the solar cell devices are investigated using temperature‐dependent current–voltage analysis and admittance spectroscopy. To investigate the observed transport barriers, a novel concept based on the differential series resistance is proposed. This approach is supported by simulations of current–voltage curves, which reproduce qualitatively experimental data. Experimentally, two parallel conduction paths are found, which act as barriers with different activation energies and impede the charge carrier transport. Both the thickness and height of these barriers increase with an increasing amount of incorporated Rb and can lead to losses in the fill factor and power conversion efficiency at room temperature. Etching in HCl prior to CdS buffer layer deposition reduces the barrier width and can recover these losses.

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Section: Discussionsupporting

confidence: 67%

“…Initially, it was found that the KF PDT causes the Cu depletion of the CIGS surface [4] and that a K-In-Se phase forms. [5][6][7][8] Additionally, shown in Figure 1f. A barrier at the front contact is introduced originating from a conduction band offset ΔE C at the iZnO/CdS interface.…”

Section: Introductionmentioning

confidence: 99%

Injection Current Barrier Formation for RbF Postdeposition‐Treated Cu(In,Ga)Se₂‐Based Solar Cells

Weiss

Nishiwaki

Bissig

et al. 2017

Adv Materials Inter

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“…In fact, a very thin RbInSe 2 layer was observed by transmission electron microscope (TEM) at the Cu(In,Ga)Se 2 /CdS interface in RbF‐treated samples, while this compound seems to be absent at the In‐free CuGaSe 2 /CdS interface . However, very little information about the chemical and physical properties of these alkali indium selenide compounds is available . Therefore, we calculated the most stable structures of these compounds by density functional theory (DFT) employing a hybrid functional ( Figure 3 a).…”

Section: Effects Of Post‐deposition Treatment With Heavy Alkalismentioning

confidence: 99%

“…It became clear early on that this treatment induces changes in the chemistry of the absorber surface . This change was found, at least in some cases, to induce a widening of the bandgap at the absorber surface, and has been attributed to the formation of a K‐In‐Se compound (KIS) layer . Also, stronger diffusion of Cd from the buffer layer into the KF treated surface was observed .…”

Section: Introductionmentioning

confidence: 99%

Heavy Alkali Treatment of Cu(In,Ga)Se₂Solar Cells: Surface versus Bulk Effects

Siebentritt

Avancini

Bär

et al. 2020

Advanced Energy Materials

126

195

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Chalcopyrite solar cells achieve efficiencies above 23%. The latest improvements are due to post‐deposition treatments (PDT) with heavy alkalis. This study provides a comprehensive description of the effect of PDT on the chemical and electronic structure of surface and bulk of Cu(In,Ga)Se2. Chemical changes at the surface appear similar, independent of absorber or alkali. However, the effect on the surface electronic structure differs with absorber or type of treatment, although the improvement of the solar cell efficiency is the same. Thus, changes at the surface cannot be the only effect of the PDT treatment. The main effect of PDT with heavy alkalis concerns bulk recombination. The reduction in bulk recombination goes along with a reduced density of electronic tail states. Improvements in open‐circuit voltage appear together with reduced band bending at grain boundaries. Heavy alkalis accumulate at grain boundaries and are not detected in the grains. This behavior is understood by the energetics of the formation of single‐phase Cu‐alkali compounds. Thus, the efficiency improvement with heavy alkali PDT can be attributed to reduced band bending at grain boundaries, which reduces tail states and nonradiative recombination and is caused by accumulation of heavy alkalis at grain boundaries.

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“…[41] A layered RbInSe 2 compound was also observed at the CdS interface by TEM measurements. [7,43] [36] As an alternative to the standard PDT procedure, the simultaneous evaporation of alkali during (In,Se) capping is also reported to positively affect V OC and devices performance.…”

Section: Beneficial Effects Of Alkali In Cigsmentioning

confidence: 99%

Advanced Alkali Treatments for High‐Efficiency Cu(In,Ga)Se₂ Solar Cells on Flexible Substrates

Carron

Nishiwaki

Feurer

et al. 2019

Advanced Energy Materials

211

165

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Flexible, lightweight Cu(In,Ga)Se2 (CIGS) solar cells grown on polymer substrates are a promising technology with fast growing market prospects. However, power conversion efficiencies of solar cells grown at low temperatures (≈450 °C) remain below the efficiencies of cells grown at high temperature on glass substrates. This contribution discusses the impact on cell efficiency of process improvements of low‐temperature CIGS deposition on flexible polyimide and glass substrates. Different strategies for incorporation of alkali elements into CIGS are evaluated based on a large number of depositions. Postdeposition treatment with heavy alkali (here RbF) enables a thickness reduction of the CdS buffer layer and increases the open‐circuit voltage. Na supply during 3rd stage CIGS deposition positively impacts the cell performance. Coevaporation of heavy alkali (e.g., RbF) during capping layer deposition mitigates the adverse shunting associated with high Cu contents, yielding highest efficiencies with near‐stoichiometric absorber compositions. Furthermore, optimization of the deposition sequence results in absorbers with a 1 µm wide notch region with nearly constant bandgap minimum. The improved processes result in a record cell efficiency of 20.8% for CIGS on flexible substrate.

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Coevaporated KInSe₂: A Fast Alternative to KF Postdeposition Treatment in High-Efficiency Cu(In,Ga)Se₂Thin Film Solar Cells

Cited by 48 publications

References 15 publications

Injection Current Barrier Formation for RbF Postdeposition‐Treated Cu(In,Ga)Se₂‐Based Solar Cells

Injection Current Barrier Formation for RbF Postdeposition‐Treated Cu(In,Ga)Se₂‐Based Solar Cells

Heavy Alkali Treatment of Cu(In,Ga)Se₂Solar Cells: Surface versus Bulk Effects

Advanced Alkali Treatments for High‐Efficiency Cu(In,Ga)Se₂ Solar Cells on Flexible Substrates

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Coevaporated KInSe2: A Fast Alternative to KF Postdeposition Treatment in High-Efficiency Cu(In,Ga)Se2Thin Film Solar Cells

Cited by 48 publications

References 15 publications

Injection Current Barrier Formation for RbF Postdeposition‐Treated Cu(In,Ga)Se2‐Based Solar Cells

Injection Current Barrier Formation for RbF Postdeposition‐Treated Cu(In,Ga)Se2‐Based Solar Cells

Heavy Alkali Treatment of Cu(In,Ga)Se2Solar Cells: Surface versus Bulk Effects

Advanced Alkali Treatments for High‐Efficiency Cu(In,Ga)Se2 Solar Cells on Flexible Substrates

Contact Info

Product

Resources

About

Coevaporated KInSe₂: A Fast Alternative to KF Postdeposition Treatment in High-Efficiency Cu(In,Ga)Se₂Thin Film Solar Cells

Injection Current Barrier Formation for RbF Postdeposition‐Treated Cu(In,Ga)Se₂‐Based Solar Cells

Injection Current Barrier Formation for RbF Postdeposition‐Treated Cu(In,Ga)Se₂‐Based Solar Cells

Heavy Alkali Treatment of Cu(In,Ga)Se₂Solar Cells: Surface versus Bulk Effects

Advanced Alkali Treatments for High‐Efficiency Cu(In,Ga)Se₂ Solar Cells on Flexible Substrates