Article
Chemistry, Physical
Melike Babucci, Debora M. Meira, Erik Wallin, Jan Keller, Olivier Donzel-Gargand, Charlotte Platzer Bjorkman, Natalia M. Martin
Summary: Alloying CIGS solar cell absorber with silver can improve the performance of thin-film solar cells by increasing the optical band gap and open-circuit voltage. By using angle-resolved XAS and other measurement techniques, it is found that the local atomic arrangement of ACIGS absorbers with varying Ag content and Ga depth gradient deviates from the long-range crystallographic structure, which may affect the electronic properties of solar cells.
ACS APPLIED ENERGY MATERIALS
(2023)
Article
Energy & Fuels
Jan Keller, Patrick Pearson, Nina Shariati Nilsson, Olof Stolt, Lars Stolt, Marika Edoff
Summary: The study focused on the impact of absorber stoichiometry in ACIGS solar cells with bandgaps greater than 1.40 eV, showing that moving away from AgGaSe2 composition can reduce ordered vacancy compounds, leading to improved device performance. An inverse correlation between V-OC and J(SC) was observed, with capacitance profiling revealing enhanced carrier collection in fully depleted samples. Additionally, the measurement of a solar cell with V-OC = 0.916 V at E-g = 1.46 eV represents the highest reported value for this bandgap to date.
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
Optics
Zhaojing Hu, Yunxiang Zhang, Shuping Lin, Shiqing Cheng, Zhichao He, Chaojie Wang, Zhiqiang Zhou, Fangfang Liu, Yun Sun, Wei Liu
Summary: Different Ag treatment processes were employed to enhance the quality of CIGS thin films deposited at low temperatures, demonstrating improvements in crystallinity and device efficiency due to Ag precursor and surface treatment. The former had a more significant impact, with a reduction in Urbach energy observed with Ag doping. This study aims to provide a feasible Ag-doping process for high-quality CIGS films in low-temperature deposition processes.
CHINESE OPTICS LETTERS
(2021)
Article
Nanoscience & Nanotechnology
Hisham Aboulfadl, Kostiantyn Sopiha, Jan Keller, Jes K. Larsen, Jonathan J. S. Scragg, Clas Persson, Mattias Thuvander, Marika Edoff
Summary: Through experimental and theoretical studies, it has been found that there is a clear trend of increased alkali bulk solubility with the silver concentration in Cu(In,Ga)Se-2 absorbers, which can enhance the performance of photovoltaic devices.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Energy & Fuels
Louis Gouillart, Andrea Cattoni, Wei-Chao Chen, Julie Goffard, Lars Riekehr, Jan Keller, Marie Jubault, Negar Naghavi, Marika Edoff, Stephane Collin
Summary: The research investigates the design of ohmic and reflective back contacts for ultrathin CIGS solar cells, improving efficiency and short-circuit current density by carefully analyzing diffusion mechanisms and reactions in the interfaces and CIGS layer, addressing the detrimental reaction between CIGS and the top ITO layer.
PROGRESS IN PHOTOVOLTAICS
(2021)
Article
Chemistry, Physical
Natalia M. Martin, Tobias Torndahl, Erik Wallin, Konstantin A. Simonov, Hakan Rensmo, Charlotte Platzer-Bjorkman
Summary: The study investigates the impact of postdeposition treatments on ACIGS solar cell performance, finding that different alkali metal fluoride treatments can modify the surface composition of the ACIGS absorber layer, thereby influencing device behavior.
ACS APPLIED ENERGY MATERIALS
(2022)
Article
Energy & Fuels
Jessica de Wild, Gizem Birant, Guy Brammertz, Marc Meuris, Jef Poortmans, Bart Vermang
Summary: This study focused on the growth of ultrathin Cu(In,Ga)Se-2 (CIGS) absorber layers on Ag/AlOx stacks, resulting in improved efficiency of solar cells to almost 12%, along with enhanced fill factor, open circuit voltage, and short circuit current density. The addition of the stack led to improvements in photoluminescence (PL), time resolved PL, and an increase in light scattering and surface roughness. Furthermore, it was found that Ag was incorporated throughout the CIGS layer, and residues of the Ag/AlOx stack were observed on the Mo back contact, affecting surface roughness and scattering properties. An ammonia sulfide etching step further enhanced the efficiency to 11.7%.
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
Energy & Fuels
Shih-Chi Yang, Jordi Sastre, Maximilian Krause, Xiaoxiao Sun, Ramis Hertwig, Mario Ochoa, Ayodhya N. Tiwari, Romain Carron
Summary: This study explores the potential of producing high-efficiency solar cells at low temperatures (<=450 degrees C) by alloying CIGS with Ag to form ACIGS solar cells, which achieved an efficiency of 20.1%. Minimal efficiency degradation was observed for ACIGS absorbers deposited at lower temperatures, in contrast to more significant degradation in CIGS devices. Advanced characterization techniques revealed that the improved morphology, reduced tail states, and higher doping density in ACIGS absorbers were the key factors contributing to the higher efficiency of ACIGS devices compared to CIGS devices.
Article
Chemistry, Multidisciplinary
Yunhai Zhao, Shengjie Yuan, Qianqian Chang, Zhengji Zhou, Dongxing Kou, Wenhui Zhou, Yafang Qi, Sixin Wu
Summary: This study successfully controlled the formation of OVC phase on the surface of CIGS, and investigated the effects of OVC content on device performance. CIGS devices with optimized OVC content exhibited better performance.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Chemistry, Physical
Dongryeol Kim, Muhammad Saifullah, Yonghee Jo, Jin Gi An, Jun-Sik Cho, SeJin Ahn, Jihye Gwak, Ho Seong Lee, Joo Hyung Park
Summary: The study investigates the improvement of back electrode properties in STUT CIGSe solar cells by sulfur treatment of the ITO back electrode. The sulfur treatment results in the formation of GaSx and GaOx phases at the rear-side interface, with GaSx being more helpful for hole extraction. Optimized sulfur treatment time leads to an increase in power conversion efficiency of the solar cells.
ACS APPLIED ENERGY MATERIALS
(2022)
Article
Energy & Fuels
Shih-Chi Yang, Mario Ochoa, Ramis Hertwig, Abdessalem Aribia, Ayodhya N. Tiwari, Romain Carron
Summary: This study focuses on the modifications of the CIGS/Mo interface in Cu(In,Ga)Se-2 (CIGS) solar cells, leading to improvements in cell performance and carrier lifetime. The research shows that adjusting the back grading height effectively suppresses back interface recombination, emphasizing the importance of grading control for enhancing the performance of CIGS solar cells and devices.
PROGRESS IN PHOTOVOLTAICS
(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
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
Physics, Applied
Shinsuke Miyagawa, Kazuhiro Gotoh, Kentaro Kutsukake, Yasuyoshi Kurokawa, Noritaka Usami
Summary: The study demonstrates the positive impact of hydrogen plasma treatment on improving the efficiency of silicon heterojunction solar cells. By using Bayesian optimization, the optimization process of multiple parameters was accelerated efficiently, leading to improved carrier lifetime under optimized experimental conditions.
APPLIED PHYSICS EXPRESS
(2021)
Article
Materials Science, Multidisciplinary
Kazuhiro Gotoh, Takeya Mochizuki, Tomohiko Hojo, Yuki Shibayama, Yasuyoshi Kurokawa, Eiji Akiyama, Noritaka Usami
Summary: The impact of hydrogen desorption on the electrical properties of TiOx on crystalline silicon with SiOy interlayers was studied, showing that lower surface recombination velocity and contact resistivity can be obtained by using SiOy interlayers. Different hydrogen desorption energies suggest the excellent passivation effect of TiOx/SC2-SiOy/c-Si heterocontacts.
CURRENT APPLIED PHYSICS
(2021)
Article
Physics, Applied
Kazuhiro Gotoh, Hiroyuki Miura, Ayako Shimizu, Yasuyoshi Kurokawa, Noritaka Usami
Summary: Variable-angle spectroscopic ellipsometry analysis was used to study the impact of post-deposition annealing on the passivation performance of TiOx/SiOy/c-Si heterocontacts. It was found that annealing at specific temperatures can enhance interface passivation and prolong the lifetime.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Chemistry, Physical
Kazuhiro Gotoh, Markus Wilde, Shohei Ogura, Yasuyoshi Kurokawa, Katsuyuki Fukutani, Noritaka Usami
Summary: The study investigates the impact of oxidizing pre-treatments and post deposition annealing on the passivation performance and hydrogen distribution near the interface between crystalline silicon and hydrogenated amorphous silicon in Si heterojunction solar cells. The results show that oxidizing pre-treatments result in thicker and higher quality a-Si:H layers, leading to a significant improvement in carrier lifetime. Post deposition annealing at 200 degrees Celsius further enhances the passivation performance, indicating that the oxide interlayer can effectively suppress hydrogen desorption and maintain high hydrogen concentrations at the heterointerfaces.
APPLIED SURFACE SCIENCE
(2021)
Article
Physics, Applied
Yasuyoshi Kurokawa, Takamasa Yoshino, Kazuhiro Gotoh, Satoru Miyamoto, Noritaka Usami
Summary: BaSi2 homojunction diodes on Nb-doped TiO2 coated glass substrates were successfully fabricated using aluminum-induced crystallization (AIC) and a two-step evaporation method. Raman scattering spectra confirmed the growth of BaSi2 on TiO2:Nb, and the formation of BaSi2 diodes was observed at temperatures ranging from 475°C to 525°C during AIC. The photoresponsivity of the diodes peaked at a wavelength of 950 nm, corresponding to the bandgap of BaSi2, with the highest value obtained at an AIC temperature of 500°C. The results also showed that larger grain size in AIC-Si contributed to the improved quality and performance of BaSi2 thin films.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2022)
Article
Nanoscience & Nanotechnology
Michinobu Fujiwara, Kazuma Takahashi, Yoshihiko Nakagawa, Kazuhiro Gotoh, Takashi Itoh, Yasuyoshi Kurokawa, Noritaka Usami
Summary: The effect of low growth rate deposition (LGD) of BaSi2 on the film quality and performance of silicon heterojunction solar cells was investigated. It was found that LGD improved the crystalline structure and performance of the solar cells, with a maximum conversion efficiency of 10.62%. This improvement is attributed to the rearrangement of atoms during LGD.
Article
Energy & Fuels
Yuqing Li, Hitoshi Sai, Takuya Matsui, Zhihao Xu, Van Hoang Nguyen, Yasuyoshi Kurokawa, Noritaka Usami
Summary: This article introduces a method to fabricate nanometer-sized pyramids and investigates their application in silicon solar cells. The experimental results demonstrate that Si nanopyramids have lower reflectance and smaller etching margin, which can improve the performance of the cells while maintaining excellent surface passivation and carrier transport properties.
Article
Physics, Applied
Haitao Wang, Yasuyoshi Kurokawa, Kazuhiro Gotoh, Shinya Kato, Shigeru Yamada, Takashi Itoh, Noritaka Usami
Summary: Effective strategies for improving the performance of a droplet-based electricity generator (DEG) are proposed, including introducing an intermediate layer of cyclic transparent optical polymer (CYTOP) by adjusting the thickness, injecting ionized ions into the surface, and increasing the surface area. Positive effects of the introduction of a CYTOP layer on outputs, especially with a greater thickness, surface ionized-air modification, and larger surface area, were observed, which could promote the practical application of DEG in energy harvesting.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Keisuke Shibata, Shinya Kato, Masashi Kurosawa, Kazuhiro Gotoh, Satoru Miyamoto, Noritaka Usami, Yasuyoshi Kurokawa
Summary: Boron-doped silicon nanocrystals/amorphous silicon oxide multilayers were prepared and their properties were investigated. The electrical conductivity of the multilayers increased with a thickness of the a-SiOx layer and saturated at a certain value. The Seebeck coefficient remained constant and the thermal conductivity was independent of the a-SiOx layer thickness, with a maximum power factor obtained at a specific thickness.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Hao Luo, Van Hoang Nguyen, Kazuhiro Gotoh, Saya Ajito, Tomohiko Hojo, Yasuyoshi Kurokawa, Eiji Akiyama, Noritaka Usami
Summary: This study investigates the effect of post-oxidizing treatment (POT) on the structural, optical, and passivation performances of titanium oxide coated crystalline Si (c-Si) heterostructures prepared by the solution process. The results show that POT improves the passivation performance by oxidizing the TiOx film, c-Si surface, and forming POx.
Article
Physics, Applied
Shohei Fukaya, Kazuhiro Gotoh, Takuya Matsui, Hitoshi Sai, Yasuyoshi Kurokawa, Noritaka Usami
Summary: In this study, a simple method was proposed to investigate the effect of metallization on the surface passivation of titanium oxide (TiO x )/Si heterostructures. The relationship between implied open-circuit voltage (iV (OC)) and photoluminescence (PL) intensity imaging of solar cell precursors before metallization was studied using PL imaging technique. Based on this relationship, the quantitative evaluation of the change in iV (OC) before and after metallization on the TiO x was performed. The results showed that the iV (OC) predicted by the PL measurement decreased by 23-104 mV after metal deposition and had a good agreement with the measured V (OC) in the finished solar cells. The evaluation of iV (OC) by PL measurement provides a useful prediction of V (OC) after metallization, which helps in analyzing the passivation degradation induced by metallization.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Kazuhiro Gotoh, Ryo Ozaki, Motoo Morimura, Aki Tanaka, Yoshiko Iseki, Kyotaro Nakamura, Kazuo Muramatsu, Yasuyoshi Kurokawa, Yoshio Ohshita, Noritaka Usami
Summary: We investigated the effect of B2H6 plasma treatment on p-type hydrogenated amorphous silicon (p-a-Si:H) surfaces for high-performance silicon heterojunction (SHJ) solar cells. The boron concentration at the p-a-Si:H surface increased after the B2H6 plasma treatment, and the specific contact resistance decreased by about one-third. The power conversion efficiency of SHJ solar cells improved due to increased fill factor (FF) resulting from decreased series resistance and increased shunt resistance, which was attributed to the enhanced upward band bending at the heterointerface between transparent conductive oxide (TCO) and p-a-Si:H caused by the B2H6 plasma treatment.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Engineering, Electrical & Electronic
Yasuyoshi Kurokawa, Kaisei Sato, Keisuke Shibata, Shinya Kato, Satoru Miyamoto, Kazuhiro Gotoh, Takashi Itoh, Noritaka Usami
Summary: By thermal evaporation of Mg and face-to-face annealing (FTFA), Mg2Si thin films were obtained on a crystalline Si substrate and a P-doped hydrogenated amorphous Si thin films on a quartz substrate. FTFA suppressed Mg evaporation, Mg2Si oxidation, and Mg2Si decomposition, resulting in the formation of polycrystalline Mg2Si thin film with large grain size. The effects of annealing temperature (TA) on crystal structure and thermoelectric properties of Mg2Si thin films were investigated. A relatively high ZT value of 0.68 was achieved at 712 K for a sample prepared at TA = 623 K, attributed to increased electrical conductivity, high Seebeck coefficient of -235 mu V center dot K-1, and low thermal conductivity of 1.4-1.7 W center dot m- 1 center dot K- 1.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2023)
Article
Chemistry, Multidisciplinary
Yuqing Li, Hitoshi Sai, Calum Mcdonald, Zhihao Xu, Yasuyoshi Kurokawa, Noritaka Usami, Takuya Matsui
Summary: This study investigates the influence of nanoscale Si pyramid textures on the performance of perovskite/Si tandem solar cells. It is found that excessive texture size leads to non-uniform top-cell formation and reduced performance. However, reducing the texture size within a certain range can suppress reflection and enhance the open-circuit voltage and current of the cell.
ADVANCED MATERIALS INTERFACES
(2023)
Proceedings Paper
Energy & Fuels
Ryohei Tsubata, Kazuhiro Gotoh, Tetsuya Inoue, Yasuyoshi Kurokawa, Noritaka Usami
Summary: By utilizing NAnocrystalline Transport path in Ultrathin dielectrics for Reinforced passivating contact (NATURE contact) in crystalline silicon solar cells, it is possible to simultaneously achieve passivation and carrier extraction. The thin contact layer of 8 nm thickness demonstrates good passivation performance and can be implemented on both sides of the solar cells, opening up possibilities for various functional devices.
2021 IEEE 48TH PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC)
(2021)
