Analysis of the back contact properties of Cu(In,Ga)Se 2 solar cells employing the thermionic emission model

Neugebohrn, Nils; Hammer, Maria S.; Neerken, Janet; Parisi, J.; Riedel, I.

doi:10.1016/j.tsf.2014.10.073

Cited by 15 publications

(9 citation statements)

References 15 publications

(23 reference statements)

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“…Finally, molybdenum has been the prime substrate for most studies on CuInS 2 -based PV devices, a choice largely driven by the success achieved with Cu(In,Ga)Se 2 solar cells on this electrical back-contact. 22 Integrating Cu(In,Ga)S 2 on a transparent conductive F:SnO 2 (FTO) substrate, however, is a much more challenging task, as this material tends to react readily with sulfur to form resistive SnS x . 23,24 This implies that direct coevaporation of Cu(In,Ga)S 2 on FTO should be avoided, as SnS x would inevitably form at the absorber/back-contact interface during the initial stage of deposition.…”

Section: Introductionmentioning

confidence: 99%

Wide-Bandgap Cu(In,Ga)S₂ Photocathodes Integrated on Transparent Conductive F:SnO₂ Substrates for Chalcopyrite-Based Water Splitting Tandem Devices

Gaillard

Prasher

Chong

et al. 2019

ACS Appl. Energy Mater.

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Whole-chalcopyrite-based tandem devices for photoelectrochemical (PEC) water splitting have emerged as a promising route for obtaining ∼20% solar-to-hydrogen efficiencies. Here we pursue this approach by demonstrating integration of the top cell wide-bandgap (E G ) chalcopyrite onto a transparent conductor, which is a critical step in the realization of tandem devices. We report specifically on our efforts to synthesize photoactive Cu(In,Ga)S 2 thin films on transparent conductive F:SnO 2 (FTO), while preserving the optoelectronic properties of the FTO substrate and preventing the formation of a resistive SnS x interfacial layer. We demonstrate that such attributes can be achieved via closespace sulfurization (CSS) of lower E G Cu(In,Ga)Se 2 precursors, coevaporated on FTO at low temperature. Depending on Cu(In,Ga)Se 2 precursors' Ga and In content, the resulting Cu(In,Ga)S 2 solar absorbers have E G energies spanning from 2.05 to 2.45 eV. The CSS process, which includes a low-temperature annealing in sulfur vapor followed by a high-temperature crystallization under inert atmosphere, allowed for up to 95% Se substitution with S in the chalcopyrite lattice, tuning both E G and band edge positions that impact PEC performance. Photoelectrochemical measurements performed under AM1.5 G illumination in 0.5 M H 2 SO 4 on the 2.05 eV CuInGaS 2 photocathode revealed a saturation photocurrent density (J SAT ) of −5.25 mA/cm 2 , a value corresponding to 38% of the absorber's optical limit. We further concluded that such low J SAT originates from subpar optical absorption of Cu(In,Ga)S 2 absorbers. Future improvements of the CSS process are expected to improve material quality toward our end goal of achieving whole-chalcopyrite tandem PEC devices.

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Section: Introductionmentioning

confidence: 99%

Wide-Bandgap Cu(In,Ga)S₂ Photocathodes Integrated on Transparent Conductive F:SnO₂ Substrates for Chalcopyrite-Based Water Splitting Tandem Devices

Gaillard

Prasher

Chong

et al. 2019

ACS Appl. Energy Mater.

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“…The electrical properties of the CIGS/FTO back contact were further investigated to clarify if the blocking diode model applies to this interface. For this analysis, the ITO/ZnO/CdS top layers of the CIGS cell were etched in a 10% HCl solution for 5 minutes and replaced by 100 nm-thick (area: 0.015 cm 2 ) gold ohmic contacts [53][54][55] evaporated directly onto the etched CIGS absorber. As presented in Figure 5(a), all J-V-T characteristics measured in dark between 300K and 140K on Au/CIGS/FTO are linear and intersects the origin, revealing that an ohmic contact, rather than a blocking barrier, is formed at the CIGS/FTO back interface.…”

Section: Ii) Early Freeze-out Of Dominant Acceptors In Cigsmentioning

confidence: 99%

Performance and limits of 2.0 eV bandgap CuInGaS₂ solar absorber integrated with CdS buffer on F:SnO₂ substrate for multijunction photovoltaic and photoelectrochemical water splitting devices

et al. 2021

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“…The rollover anomaly is described to be a current saturation in the first quadrant of the JV curve, that is, under forward bias, revealing a charge carrier injection barrier 23,32 . The first possible cause for that behavior is the presence of a back‐contact barrier representing a hole injection barrier at the CIGSe/Mo interface 23,32–38 . Another possible cause is acceptor states at the CdS/ZnO front interface 23 .…”

Section: Principle Scaps‐1d Models For Possible Degradationmentioning

confidence: 99%

Decay mechanisms in CdS‐buffered Cu(In,Ga)Se₂ thin‐film solar cells after exposure to thermal stress: Understanding the role of Na

Yetkin

Kodalle

Bertram

et al. 2021

Progress in Photovoltaics

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Due to their tunable bandgap energy, Cu(In,Ga)Se2 (CIGSe) thin‐film solar cells are an attractive option for use as bottom devices in tandem configurations. In monolithic tandem devices, the thermal stability of the bottom device is paramount for reliable application. Ideally, it will permit the processing of a top device at the required optimum process temperature. Here, we investigate the degradation behavior of chemical bath deposited (CBD) CdS‐buffered CIGSe thin‐film solar cells with and without Na incorporation under thermal stress in ambient air and vacuum with the aim to gain a more detailed understanding of their degradation mechanisms. For the devices studied, we observe severe degradation after annealing at 300°C independent of the atmosphere. The electrical and compositional properties of the samples before and after a defined application of thermal stress are studied. In good agreement with literature reports, we find pronounced Cd diffusion into the CIGS absorber layer. In addition, for Na‐containing samples, the observed degradation can be mainly explained by the formation of Na‐induced acceptor states in the TCO front contact and a back contact barrier formation due to the out‐diffusion of Na. Supported by numerical device simulation using SCAPS‐1D, various possible degradation models are discussed and correlated with our findings.

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Analysis of the back contact properties of Cu(In,Ga)Se 2 solar cells employing the thermionic emission model

Cited by 15 publications

References 15 publications

Wide-Bandgap Cu(In,Ga)S₂ Photocathodes Integrated on Transparent Conductive F:SnO₂ Substrates for Chalcopyrite-Based Water Splitting Tandem Devices

Wide-Bandgap Cu(In,Ga)S₂ Photocathodes Integrated on Transparent Conductive F:SnO₂ Substrates for Chalcopyrite-Based Water Splitting Tandem Devices

Performance and limits of 2.0 eV bandgap CuInGaS₂ solar absorber integrated with CdS buffer on F:SnO₂ substrate for multijunction photovoltaic and photoelectrochemical water splitting devices

Decay mechanisms in CdS‐buffered Cu(In,Ga)Se₂ thin‐film solar cells after exposure to thermal stress: Understanding the role of Na

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Analysis of the back contact properties of Cu(In,Ga)Se 2 solar cells employing the thermionic emission model

Cited by 15 publications

References 15 publications

Wide-Bandgap Cu(In,Ga)S2 Photocathodes Integrated on Transparent Conductive F:SnO2 Substrates for Chalcopyrite-Based Water Splitting Tandem Devices

Wide-Bandgap Cu(In,Ga)S2 Photocathodes Integrated on Transparent Conductive F:SnO2 Substrates for Chalcopyrite-Based Water Splitting Tandem Devices

Performance and limits of 2.0 eV bandgap CuInGaS2 solar absorber integrated with CdS buffer on F:SnO2 substrate for multijunction photovoltaic and photoelectrochemical water splitting devices

Decay mechanisms in CdS‐buffered Cu(In,Ga)Se2 thin‐film solar cells after exposure to thermal stress: Understanding the role of Na

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Wide-Bandgap Cu(In,Ga)S₂ Photocathodes Integrated on Transparent Conductive F:SnO₂ Substrates for Chalcopyrite-Based Water Splitting Tandem Devices

Wide-Bandgap Cu(In,Ga)S₂ Photocathodes Integrated on Transparent Conductive F:SnO₂ Substrates for Chalcopyrite-Based Water Splitting Tandem Devices

Performance and limits of 2.0 eV bandgap CuInGaS₂ solar absorber integrated with CdS buffer on F:SnO₂ substrate for multijunction photovoltaic and photoelectrochemical water splitting devices

Decay mechanisms in CdS‐buffered Cu(In,Ga)Se₂ thin‐film solar cells after exposure to thermal stress: Understanding the role of Na