Article
Nanoscience & Nanotechnology
Takehiko Nagai, Jiro Nishinaga, Hitoshi Tampo, Shinho Kim, Kazuhiro Hirayama, Tatsuo Matsunobe, Guanzhong Chen, Yuya Ide, Shogo Ishizuka, Hajime Shibata, Shigeru Niki, Norio Terada
Summary: In this study, we investigated the band alignments at CdS/epitaxial CuInxGa1-xSe2 (epi-CIGSe) and epi-CIGSe/GaAs heterointerfaces for solar cell applications using photoemission spectroscopy techniques. The impact of KF postdeposition treatment (KF-PDT) on the band alignment at the CdS/epi-CIGSe front heterointerface was clarified. We found that KF-PDT changed the conduction band alignment by altering the electron affinity and ionization potential of the epi-CIGSe surface. Additionally, band alignment at the epi-CIGSe/GaAs rear heterointerface was investigated, showing the formation of electron barriers and a hole accumulation layer.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Chemistry, Physical
Jakapan Chantana, Bobur Ergashev, Yu Kawano, Yukiko Kamikawa, Shogo Ishizuka, Takashi Minemoto
Summary: CIGSe solar cells were fabricated on SLG substrates with the structure of Al/Ni/sputtered Zn(0.88)Mg(0.12)O:Al TCO/sputtered Zn1-xMgxO 2nd buffer/CdS 1st buffer/CIGSe/Mo/SLG. The impact of CBO2 between CIGSe absorber and Zn1-xMgxO 2nd buffer on cell performance and carrier recombination was investigated experimentally and theoretically. The optimization of CBO2 reduced carrier recombination, improved band bending, and increased the conversion efficiency up to 20.0%. With an antireflective coating layer, the CIGSe solar cell achieved a conversion efficiency of 21.1% with the optimized CBO2.
ACS APPLIED ENERGY MATERIALS
(2023)
Article
Energy & Fuels
Jan Keller, Hisham Aboulfadl, Lars Stolt, Olivier Donzel-Gargand, Marika Edoff
Summary: This contribution investigates the potential of RbF postdeposition treatment on ACIGS solar cells. It is found that while the open-circuit voltage and short-circuit current density can be improved, the fill factor decreases. However, for some stoichiometric samples, the drop in fill factor can be avoided, resulting in higher efficiencies. Extensive material analysis reveals that the treatment leads to modifications in the absorber layer and restricted diffusion of rubidium. A thin RbInSe2 surface layer is also suggested.
Article
Energy & Fuels
Nour El I. Boukortt, Mabrouk Adouane, Rawan AlHammadi
Summary: The research investigated the impact of various factors on ultrathin CIGS solar cell performance, finding that using thin film Al2O3 for rear-passivation can significantly improve cell performance by reducing rear side contact recombination losses. However, poor passivation was observed with high density of positive charge or high contact resistance at the interface. The optimal combination led to achieving the best cell performance.
Article
Energy & Fuels
Ryotaro Fukuda, Takahito Nishimura, Akira Yamada
Summary: The behavior of carriers for an electron-beam-induced current (EBIC) evaluation in polycrystalline Cu(In, Ga)Se-2 (CIGS) thin-film solar cells was experimentally and theoretically analyzed. The analysis revealed four features in the EBIC signal profiles of the CIGS layers: peaks at grain boundaries (GBs), narrowed peaks near the surface, shifted peaks near the surface, and double peaks at the GBs and surface. These findings will contribute to a comprehensive understanding of the carrier transport mechanism in polycrystalline CIGS, which is crucial for achieving high-efficiency CIGS solar cells.
PROGRESS IN PHOTOVOLTAICS
(2023)
Article
Nanoscience & Nanotechnology
Marin Rusu, Tim Kodalle, Leo Choubrac, Nicolas Barreau, Christian A. Kaufmann, Rutger Schlatmann, Thomas Unold
Summary: The study shows that KF-PDT and RbF-PDT have a significant impact on the electronic properties of CIGSe thin films and the CdS/CIGSe interface, with the CIGSe surface band gap depending on the type of postdeposition treatment and a thin layer with a graded band gap found at the CdS/CIGSe interface. K and Rb act as compensating acceptors in the CdS layer.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Energy & Fuels
Diego A. Garzon, Christian Rossi, Ishwor Khatri, Francesco Soggia, Ihsan Caha, Francis Leonard Deepak, Diego Colombara, Sascha Sadewasser
Summary: The formation of Cd-free Zn1-xSnxOy (ZTO) thin film buffer layers for CIGSe solar cells was studied using chemical bath deposition. By modifying the deposition procedure, flatter ZTO films were obtained with inhibited columnar growth. Increasing the concentration of Sn in the chemical bath resulted in a nontrivial increase in the bandgap. Using a 20% Sn concentration, the CIGSe solar cells achieved similar performance to those with a CdS buffer layer, with a maximum efficiency of 10.4% and an average efficiency of 9%.
Article
Energy & Fuels
Bing Li, Aimei Zhao, Dongmei Xiang, Zhuo Peng, Yujie Yuan, Yupeng Xing, Liyong Yao, Jinlian Bi, Wei Li
Summary: In this study, an Ag buffer layer was used to eliminate the nonuniform distribution of Cu on Mo, resulting in improved crystallinity and performance of ACIGSe absorber and solar cells.
Article
Materials Science, Multidisciplinary
Mariana Montoya-Gomez, Stefan Paetel, Wolfram Hempel, Ana Kanevce, Theresa Magorian Friedlmeier, Dimitrios Hariskos
Summary: Cu(In,Ga)Se2-based solar cells achieve highest efficiencies up to 23.4% by using solution-grown Zn(O,S) as the buffer layer. We test the impact of oxidative and reductive additives on the growth rate of Zn(O,S) and find that both additives can significantly increase the growth rate and reduce the consumption of reactants without compromising the performance of the solar cells.
Article
Energy & Fuels
Ara Cho, Inyoung Jeong, Soomin Song, Donghyeop Shin, Sangmin Lee, Kihwan Kim, Jae Ho Yun, Jun Sik Cho, Joo Hyung Park
Summary: Using a QCM system to accurately obtain an adjustable CdS layer, researchers examined the characteristics and performances of 30 nm-thick CdS layers compared to conventional 60 nm-thick CdS buffer. Most CIGS solar cells with the 30 nm-thick CdS buffer showed higher efficiency than those with the 60 nm-thick CdS buffer due to improved J(sc), despite CIGS with the 30 nm CdS formed in the middle range exhibiting the lowest photovoltaic performance. Further analysis on all deposited CdS layers and the effect of heat treatment was conducted to explain these results.
Article
Materials Science, Multidisciplinary
Wolfram Witte, Stefan Paetel, Richard Menner, Andreas Bauer, Dimitrios Hariskos
Summary: Crystalline gallium oxide is a promising wide-bandgap semiconductor material suitable for high-frequency and high-power devices, as well as thin-film solar cells. X-ray amorphous gallium oxide deposited by RF magnetron sputtering serves as an n-type buffer layer in solar cells, improving efficiency.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2021)
Article
Energy & Fuels
Latha Marasamy, Aruna-Devi Rasu Chettiar, Francisco de Moure-Flores, Velumani Subramaniam
Summary: The CGI ratio in CIGSe semiconductor plays a crucial role in solar energy conversion. This study demonstrates the impact of varying CGI values on the structural, morphological, and electrical properties of CIGSe, showing significant changes in bandgap energy, crystal diameter, crystal shape, carrier concentration, mobility, and resistivity. The findings suggest that tuning the CGI value through a low-cost solution process can greatly enhance the properties of CIGSe solar cell absorbers.
INTERNATIONAL JOURNAL OF ENERGY RESEARCH
(2021)
Article
Chemistry, Physical
Diego Colombara, Billy J. Stanbery, Giovanna Sozzi
Summary: The commercial attractiveness of Cu(In,Ga) (S,Se)(2) (CIGS) photovoltaics is limited by the research and development gap compared to silicon. Overcoming this gap requires strategic approaches and extensive research and development in both industry and lab scale. However, the technological progress relies on our understanding of diffusion phenomena during and after the absorber growth, particularly in combination with alkali metal doping.
JOURNAL OF MATERIALS CHEMISTRY A
(2023)
Article
Physics, Applied
Aaron S. Gehrke, David E. Sommer, Scott T. Dunham
Summary: In order to improve the performance of Cu(In,Ga)Se-2 thin-film photovoltaic devices, this study investigates the diffusion pathways of In and Ga. Density functional theory is used to identify the most probable defect complexes and mechanisms, as well as calculate their binding energies and migration barriers. Analytic models and simulations are employed to predict the diffusivity of In and Ga under various conditions.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Energy & Fuels
Dirk Hauschild, Mary Blankenship, Amandee Hua, Ralph Steininger, Patrick Eraerds, Thomas Niesen, Thomas Dalibor, Wanli Yang, Clemens Heske, Lothar Weinhardt
Summary: The chemical and electronic structure of the interface between a sputter-deposited Zn(O,S) buffer layer and an industrial Cu(In,Ga)(S,Se)(2) (CIGSSe) absorber for thin-film solar cells was investigated using various spectroscopic techniques. It was found that the CIGSSe absorber surface band gap significantly increased compared to bulk-sensitive methods. The measurements also showed the presence of S-Zn and S-O bonds in the Zn(O,S) layer, and an enhanced carrier separation at the interface.
Article
Energy & Fuels
Kikuo Makita, Yukiko Kamikawa, Hidenori Mizuno, Ryuji Oshima, Yasushi Shoji, Shogo Ishizuka, Ralph Mueller, Paul Beutel, David Lackner, Jan Benick, Martin Hermle, Frank Dimroth, Takeyoshi Sugaya
Summary: The study developed an InGaP/AlGaAs//CuxIn1-yGaySe2 three-junction solar cell using adhesive material and a Pd nanoparticle array, achieving a total efficiency of 27.2% under AM 1.5 G illumination. The reliability of the solar cells was confirmed through a heat cycle test, showing high resistivity under severe conditions. The results demonstrate the potential of III-V//CuxIn1-yGaySe2 MJ solar cells for next-generation photovoltaic applications.
PROGRESS IN PHOTOVOLTAICS
(2021)
Article
Energy & Fuels
Alban Lafuente-Sampietro, Katsuhisa Yoshida, Shenghao Wang, Shogo Ishizuka, Hajime Shibata, Nobuyuki Sano, Katsuhiro Akimoto, Takeaki Sakurai
Summary: In this article, the effect of the double grading in a CIGS absorber is studied from the carrier perspective. It is found that finding the ideal notch position to maximize carrier collection while minimizing recombination rate is a compromise process.
SOLAR ENERGY MATERIALS AND SOLAR CELLS
(2021)
Article
Physics, Applied
Hamidou Tangara, Yulu He, Muhammad Monirul Islam, Shogo Ishizuka, Takeaki Sakurai
Summary: It has been found that heat light soaking (HLS) can increase the net doping density of CIGS solar cells, but has a lower than expected improvement on the open-circuit voltage (V (OC)). Analysis based on the SQ theory reveals that HLS reduces the nonradiative recombination rate in the bulk but increases it at the interface. A combination of HLS and KF/NaF-PDT is necessary to enhance the positive impacts of HLS and mitigate the detrimental ones leading to high-efficiency CIGS devices (22%).
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Chemistry, Physical
Shogo Ishizuka, Jiro Nishinaga, Kosuke Beppu, Tsuyoshi Maeda, Fuuka Aoyagi, Takahiro Wada, Akira Yamada, Jakapan Chantana, Takahito Nishimura, Takashi Minemoto, Muhammad Monirul Islam, Takeaki Sakurai, Norio Terada
Summary: This paper reviews current issues in physical and chemical studies of CISe-based materials and devices, focusing on areas such as correlations between Cu-deficient phases and alkali-metals effects, applications to lightweight and flexible solar minimodules, single-crystalline epitaxial Cu(In,Ga)Se-2 films and devices, differences between Cu(In,Ga)Se-2 and Ag(In,Ga)Se-2 materials, wide-gap CuGaSe2 films and devices, all-dry processed CISe-based solar cells with high photovoltaic efficiencies, and fundamental studies on open circuit voltage loss analysis and energy band structure at the interface.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Jiro Nishinaga, Shogo Ishizuka
Summary: This study investigates the effects of KF-PDT and NaF doping on the conversion efficiency of Cu(In,Ga)Se-2(CIGS) solar cells. It is found that these treatments have positive effects on efficiency even when using Cu stoichiometric CIGS layers. The study also shows that NaF doping and KF-PDT increase the minority carrier lifetimes, similar to polycrystalline CIGS solar cells.
Article
Nanoscience & Nanotechnology
Takehiko Nagai, Jiro Nishinaga, Hitoshi Tampo, Shinho Kim, Kazuhiro Hirayama, Tatsuo Matsunobe, Guanzhong Chen, Yuya Ide, Shogo Ishizuka, Hajime Shibata, Shigeru Niki, Norio Terada
Summary: In this study, we investigated the band alignments at CdS/epitaxial CuInxGa1-xSe2 (epi-CIGSe) and epi-CIGSe/GaAs heterointerfaces for solar cell applications using photoemission spectroscopy techniques. The impact of KF postdeposition treatment (KF-PDT) on the band alignment at the CdS/epi-CIGSe front heterointerface was clarified. We found that KF-PDT changed the conduction band alignment by altering the electron affinity and ionization potential of the epi-CIGSe surface. Additionally, band alignment at the epi-CIGSe/GaAs rear heterointerface was investigated, showing the formation of electron barriers and a hole accumulation layer.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Energy & Fuels
Kikuo Makita, Yukiko Kamikawa, Hidenori Mizuno, Ryuji Oshima, Yasushi Shoji, Shogo Ishizuka, Ralph Mueller, David Lackner, Frank Dimroth, Takeyoshi Sugaya
Summary: A highly efficient InGaP/Al$_0.06$Ga$_0.94$As//CIGSe three-junction solar cell was successfully fabricated using a new smart stack technology, achieving a total efficiency of 28.06%, the highest efficiency ever reported for GaAs//CIGSe-based tandem solar cells.
IEEE JOURNAL OF PHOTOVOLTAICS
(2022)
Article
Energy & Fuels
Kikuo Makita, Yukiko Kamikawa, Takashi Koida, Hidenori Mizuno, Ryuji Oshima, Yasushi Shoji, Shogo Ishizuka, Tatsuya Takamoto, Takeyoshi Sugaya
Summary: This study presents a highly efficient InGaP/GaAs//CIGSe three-junction solar cell with an efficiency of 29.3% for the aperture area, the highest reported for GaAs//CIGSe-based tandem solar cells. The improved performance is achieved by using a modified smart stack technology and a specialized CIGSe cell with a flattened surface and a thin In2O3;Ce,H transparent conducting oxide layer.
PROGRESS IN PHOTOVOLTAICS
(2023)
Article
Energy & Fuels
Yukiko Kamikawa, Taizo Masuda, Jiro Nishinaga, Shogo Ishizuka
Summary: This study investigated the influence of Ar background pressure on the properties of Mo back contact on polyimide films. High Ar pressure caused crack formation in the Mo layer and decreased fill factor, while reducing the Ar pressure improved the fill factor. Additionally, the stress condition of Mo also affected the thermal diffusion of alkali metal.
Article
Chemistry, Multidisciplinary
Shogo Ishizuka, Riku Okamoto, Shigeru Ikeda
Summary: This article discusses the efficiency of solar cells and photocathodes using CGSe photoabsorber layers and highlights the importance of interface modification in controlling energy conversion device parameters.
ADVANCED MATERIALS INTERFACES
(2022)
Article
Energy & Fuels
Takeshi Tayagaki, Ayumi Sasaki, Shogo Ishizuka, Masahiro Yoshita
Summary: This article investigates the effect of shunt resistances on the performance of curved thin-film photovoltaic (PV) modules. It finds that low shunt resistance can reduce current mismatch and power loss, and enhance module durability.
IEEE JOURNAL OF PHOTOVOLTAICS
(2022)
Article
Physics, Applied
Jiro Nishinaga, Manabu Togawa, Masaya Miyahara, Kosuke Itabashi, Hironori Okumura, Masataka Imura, Yukiko Kamikawa, Shogo Ishizuka
Summary: Radiation tolerance of Cu(In,Ga)Se-2 (CIGS) solar cells was investigated for application in extremely-high-radiation environments. The cells deteriorated after high-energy proton irradiation but could still generate power. Recombination centers in CIGS layers increased after irradiation, but heat-light annealing partially passivated them. Dark annealing also had a beneficial effect on passivating recombination centers, even with thicker CIGS layers.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Hajime Shibata, Jiro Nishinaga, Yukiko Kamikawa, Hitoshi Tampo, Takehiko Nagai, Takashi Koida, Shogo Ishizuka, Toshimitsu Mochizuki, Masafumi Yamaguchi
Summary: The optoelectronic reciprocity theorem relates electroluminescence (EL) and photovoltaic external quantum efficiency in solar cells and is crucial for understanding solar cell operation and device evaluation. It also allows for estimating the open-circuit voltage (VOC) using the external radiative efficiency (riext) obtained from EL emission intensity. This study confirms the validity of the optoelectronic reciprocity theorem for high-efficiency CuIn1-xGaxSe2 (CIGS) solar cells and demonstrates that the diode ideality factor is unity for band-edge emission due to direct recombination.
PHYSICAL REVIEW APPLIED
(2023)
Article
Chemistry, Physical
Jakapan Chantana, Bobur Ergashev, Yu Kawano, Yukiko Kamikawa, Shogo Ishizuka, Takashi Minemoto
Summary: CIGSe solar cells were fabricated on SLG substrates with the structure of Al/Ni/sputtered Zn(0.88)Mg(0.12)O:Al TCO/sputtered Zn1-xMgxO 2nd buffer/CdS 1st buffer/CIGSe/Mo/SLG. The impact of CBO2 between CIGSe absorber and Zn1-xMgxO 2nd buffer on cell performance and carrier recombination was investigated experimentally and theoretically. The optimization of CBO2 reduced carrier recombination, improved band bending, and increased the conversion efficiency up to 20.0%. With an antireflective coating layer, the CIGSe solar cell achieved a conversion efficiency of 21.1% with the optimized CBO2.
ACS APPLIED ENERGY MATERIALS
(2023)
Article
Engineering, Electrical & Electronic
Shogo Ishizuka, Yukiko Kamikawa, Jiro Nishinaga
Summary: This communication presents the prospects of Cu(In,Ga)Se-2 (CIGS)-based lightweight and flexible photovoltaic devices, discusses the current status of flexible CIGS minimodules and future directions to enhance their efficiency, and explores the effects of cell separation edges on device performance.
NPJ FLEXIBLE ELECTRONICS
(2022)
