【公開日：2025.06.10】【最終更新日：2025.04.15】
課題データ / Project Data
課題番号 / Project Issue Number
24NU0041
利用課題名 / Title
Nanostructure and nucleation phenomena during in-situ synthesis of Cu2ZnSnSe4 thin films
利用した実施機関 / Support Institute
名古屋大学 / Nagoya Univ.
機関外・機関内の利用 / External or Internal Use
外部利用/External Use
技術領域 / Technology Area
【横断技術領域 / Cross-Technology Area】（主 / Main）計測・分析/Advanced Characterization（副 / Sub）-
【重要技術領域 / Important Technology Area】（主 / Main）革新的なエネルギー変換を可能とするマテリアル/Materials enabling innovative energy conversion（副 / Sub）次世代ナノスケールマテリアル/Next-generation nanoscale materials
キーワード / Keywords
電子顕微鏡/ Electronic microscope,太陽電池/ Solar cell
利用者と利用形態 / User and Support Type
利用者名（課題申請者）/ User Name (Project Applicant)
Klaus Liefer
所属名 / Affiliation
Uppsala University, Engineering Science
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
武藤 俊介
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
荒井 重勇
利用形態 / Support Type
（主 / Main）共同研究/Joint Research（副 / Sub）-
利用した主な設備 / Equipment Used in This Project
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
Solar cells are in the focus of efforts to reduce CO2 emissions as well as to build a more sustainable world. Despite of the tremendous progress in solar cell development and fabrication, to date, most solar cells contain rare and toxic elements. Therefore, kesterite solar cells like Cu2ZnSnSe4 containing only earth abundant elements, are an excellent candidate for building sustainable solar cells. The increase in kesterite solar cell efficiency over the last decade is considerable, though a detailed understanding of the evolution of the structure in the synthesis process has not yet been addressed by microscopy techniques. A nanoscopic analysis of grain nucleation, growth and diffusion pathways using transmission electron microscopy (TEM) has therefore a high potential to foster understanding of the synthesis process as well as contribute to the improvement of such solar cells. In the preceding two-year study, we successfully established a very challenging scheme of in situ dynamical observation scheme using the RS-HVEM-QMS system, only available in Nagoya. We already obtained several useful information on the growth mechanism of kersterite, but silicon substrate on which the precursor materials were deposited was found to be evaporate during the heating process. So, we would like to extend the project for another year and repeat the same experiment with improved sample systems.
実験 / Experimental
We carried out the first preliminary
experiments at Nagoya University two years ago to demonstrate the feasibility
of such in-situ experiment and could setup the experiment in the TEM, determine
the temperature range at which Se gets absorbed in the sample, observe the
first nucleation of grains and carry out EELS analysis at elevated temperature.
In this academic year we will repeat similar experiments at the HVEM laboratory
in collaboration with Professor Muto, who developed HVEM-QMS system. The main
interests focus on:
-
Grain growth at different temperatures starting at
about 300°C.
-
Relate desorption/adsorption of atoms and molecules
with nucleation and growth of layers using the mass spectrometer and advanced
diffraction, imaging and EELS techniques.
-
Obtain the first grains of Cu2ZnSnSe4 kesterite
phase.
- Grow the grain size and learn how the growth will
impact and possibly passivate the atomic scale structure of grain boundaries.
結果と考察 / Results and Discussion
We started the synthesis either from the metallic stacks or from Cu2ZnSnS4 which are
exposed to Se vapours. Though the analysis of the metallic stacks has promising results, the
thickness increase of about a factor of 2 during the selenisation process made the sample so
thick that it was difficult to analyse nanometric changes in the sample happening during the
synthesis process. This situation changed by using thin Cu2ZnSnS4 and AgCu2ZnSnS4 films as
a starting material since these films preserve their thickness during the synthesis.
During the in-situ annealing of AgCu2ZnSnS4, we observed the nucleation of the kesterite
Cu2ZnSn(S)Se4 phase, which is precedented by the formation of Ag- and Se-containing
nanoprecipitates. Those partially disappear during higher annealing temperatures, when the
AgCu2ZnSnSe4 grains grow. By in-situ EELS analysis and post-annealing EDS measurements of
the thin layers we could follow the chemical modifications of the crystallites forming a core
shell structure.
When the Cu2ZnSnS4 is synthesised, the replacement of S by Se causes an expansion of the
lattice parameter. We applied a Hough transform to extract the lattice plane spacing from the
diffraction patterns and conclude that in Cu2ZnSnS(4-x)Sex, Se is inserted at a concentration
of 50±10 %. One goal of this annealing process is to increase the grain size to reduce the
impact of grain boundaries on carrier transport. Whereas the starting kesterite has a grain
size in the 10 nm range, after the annealing process, a grain size of 50 nm is reached.
As conclusion, using in situ HVTEM synthesis of Cu2ZnSn S(1-x)Sex kesterite structures, we could
successfully demonstrate the grain growth and replacement of S by Se in the kesterite
crystal. This replacement reaction happens at elevated temperatures of 400-500 °C.
図・表・数式 / Figures, Tables and Equations
TEM image and EDS mapping results of Ag and Se precipitates during the in situ synthesis
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
This work is partly supported by IMaSS joint usage/joint research program (International collaboration) of Insitute of Materials & Systems for Sustainability, Nagoya University.
成果発表・成果利用 / Publication and Patents
論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)
-
Klaus Leifer, In-situ synthesis of thin kesterite films using high voltage TEM, BIO Web of Conferences, 129, 25056(2024).
DOI: https://doi.org/10.1051/bioconf/202412925056
口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.
特許 / Patents
特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件