Macroscopic and microscopic electrical properties of Cu(In,Ga)Se2 thin-film solar cells with various Ga/(In+Ga) contents

Kim, Gee Yeong; Jo, William; Jo, Hyun-Jun; Kim, Dae Hwan; Kang, Jin Kyu

doi:10.1016/j.cap.2015.04.036

Cited by 10 publications

(5 citation statements)

References 29 publications

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“…This illustration highlights the GBs as the main conduction channels, particularly, when an external bias is applied to the sample emitting electrons from the samples to the grounded tip. 24 The samples with alkali PDT showed enhanced formation of the surface current presumably due to the increased carrier concentrations. Additionally, Sharma et al recently demonstrated that the CIGS thin lm treated with Rb and Cs possessed higher carrier concentrations and enhanced homogeneity of carrier concentration.…”

Section: Resultsmentioning

confidence: 95%

Interplay Between Strain and Charge in Cu(In,Ga)Se2 Flexible Photovoltaics

Jo,

Park,

Yim

et al. 2024

Preprint

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Flexible and lightweight Cu(In,Ga)Se2 (CIGS) thin-film solar cells are promising for versatile applications, but there is limited understanding of stress-induced changes. In this study, the charge carrier generation and trapping behavior under mechanical stress was investigated using flexible CIGS thin-film solar cells with various alkali treatments. Surface current at the CIGS surface decreased by convex bending, which occurs less with the incorporation of alkali metals. The formation energy of the carrier generating defects increased in convex bending environments clarifying the degradation of the surface current. Moreover, alkali-related defects had lower formation energy than the intrinsic acceptors, mitigating current degradation in mechanical stress condition. The altered defect energy levels were attributed to the deformation of the crystal structure under bending states. This study provides insights into the mitigating of strain-induced charge degradation for enhancing the performance and robustness of flexible CIGS photovoltaic devices. Furthermore, direct atomic force microscopy-based probing techniques on bent material surfaces can contribute to the understanding of interplay between the strain and charge in other flexible optoelectronic devices.

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Section: Resultsmentioning

confidence: 95%

Interplay Between Strain and Charge in Cu(In,Ga)Se2 Flexible Photovoltaics

Jo,

Park,

Yim

et al. 2024

Preprint

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“…The overall Cu/(Ga + In) (CGI) ratio was 0.86 for all the samples, whereas the Ga/(Ga + In) (GGI) ratios were 0.34, 0.33, and 0.32 for samples A, B, and C, respectively. In our previous study, it was found that the optimal GGI ratio results in a significant improvement in the electrical properties, such as a high shunt resistance and low series resistance . Furthermore, the elemental distribution was measured using SIMS.…”

Section: Resultsmentioning

confidence: 99%

Tailored Band Structure of Cu(In,Ga)Se₂ Thin-Film Heterojunction Solar Cells: Depth Profiling of Defects and the Work Function

Park

Cho

Kim

et al. 2022

ACS Appl. Mater. Interfaces

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An efficient carrier transport is essential for enhancing the performance of thin-film solar cells, in particular Cu(In,Ga)Se2 (CIGS) solar cells, because of their great sensitivities to not only the interface but also the film bulk. Conventional methods to investigate the outcoming carriers and their transport properties measure the current and voltage either under illumination or dark conditions. However, the evaluation of current and voltage changes along the cross-section of the devices presents several limitations. To mitigate this shortcoming, we prepared gently etched devices and analyzed their properties using micro-Raman scattering spectroscopy, Kelvin probe force microscopy, and photoluminescence measurements. The atomic distributions and microstructures of the devices were investigated, and the defect densities in the device bulk were determined via admittance spectroscopy. The effects of Ga grading on the charge transport at the CIGS–CdS interface were categorized into various types of band offsets, which were directly confirmed by our experiments. The results indicated that reducing open-circuit voltage loss is crucial for obtaining a higher power conversion efficiency. Although the large Ga grading in the CIGS absorber induced higher defect levels, it effectuated a smaller open-circuit voltage loss because of carrier transport enhancement at the absorber–buffer interface, resulting from the optimized conduction band offsets.

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“…Conversely, the downward E c band bending structure at the GBs can enhance the electron collection at the GBs. CIGSe mainly shows a downward E c band bending structure at the GBs 20–22 ; in CZTSSe, downward 23–28 or upward 7,9,27–31 E c band bending structures at the GBs are observed. Kelvin probe force microscopy (KPFM) is a useful method to identify the surface potential of an absorber surface 32,33 .…”

Section: Introductionmentioning

confidence: 96%

“…These surface local current characteristics can be identified using conducting atomic force microscopy (c-AFM). 7,9,[20][21][22][23][25][26][27][28]34 The elemental variations between the IGs and GBs can cause band bending at the GBs. Using atom probe tomography (APT), the characteristics of the elemental variations between the IGs and GBs in the CIGSe [35][36][37][38][39][40][41] and CZTSSe [42][43][44] absorbers were reported.…”

Section: Introductionmentioning

confidence: 99%

“…A local current forms in the IGs when the E c band bends upward at the GBs; conversely, a local current forms at the GBs when the E c band bends downward at the GBs. These surface local current characteristics can be identified using conducting atomic force microscopy (c‐AFM) 7,9,20–23,25–28,34 . The elemental variations between the IGs and GBs can cause band bending at the GBs.…”

Section: Introductionmentioning

confidence: 99%

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Vertical plane depth‐resolved surface potential and carrier separation characteristics in flexible CZTSSe solar cells with over 12% efficiency

Son,

Park,

Kim

et al. 2024

Carbon Energy

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Cu2ZnSn(S,Se)4 (CZTSSe) solar cells have resource distribution and economic advantages. The main cause of their low efficiency is carrier loss resulting from recombination of photo‐generated electron and hole. To overcome this, it is important to understand their electron‐hole behavior characteristics. To determine the carrier separation characteristics, we measured the surface potential and the local current in terms of the absorber depth. The elemental variation in the intragrains (IGs) and at the grain boundaries (GBs) caused a band edge shift and bandgap (Eg) change. At the absorber surface and subsurface, an upward Ec and Ev band bending structure was observed at the GBs, and the carrier separation was improved. At the absorber center, both upward Ec and Ev and downward Ec‐upward Ev band bending structures were observed at the GBs, and the carrier separation was degraded. To improve the carrier separation and suppress carrier recombination, an upward Ec and Ev band bending structure at the GBs is desirable.

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Macroscopic and microscopic electrical properties of Cu(In,Ga)Se2 thin-film solar cells with various Ga/(In+Ga) contents

Cited by 10 publications

References 29 publications

Interplay Between Strain and Charge in Cu(In,Ga)Se2 Flexible Photovoltaics

Interplay Between Strain and Charge in Cu(In,Ga)Se2 Flexible Photovoltaics

Tailored Band Structure of Cu(In,Ga)Se₂ Thin-Film Heterojunction Solar Cells: Depth Profiling of Defects and the Work Function

Vertical plane depth‐resolved surface potential and carrier separation characteristics in flexible CZTSSe solar cells with over 12% efficiency

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Macroscopic and microscopic electrical properties of Cu(In,Ga)Se2 thin-film solar cells with various Ga/(In+Ga) contents

Cited by 10 publications

References 29 publications

Interplay Between Strain and Charge in Cu(In,Ga)Se2 Flexible Photovoltaics

Interplay Between Strain and Charge in Cu(In,Ga)Se2 Flexible Photovoltaics

Tailored Band Structure of Cu(In,Ga)Se2 Thin-Film Heterojunction Solar Cells: Depth Profiling of Defects and the Work Function

Vertical plane depth‐resolved surface potential and carrier separation characteristics in flexible CZTSSe solar cells with over 12% efficiency

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Product

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Tailored Band Structure of Cu(In,Ga)Se₂ Thin-Film Heterojunction Solar Cells: Depth Profiling of Defects and the Work Function