Perovskites and Novel Low-Temperature A3B5 Semiconductor Materials: Research and Advanced Characterisation
Research Project KP-06 Danube/5 /11.07.2025 (RIS 2987)
funded by the Bulgarian Science Research Fund, Ministry of Education
"Multilateral Competition for Scientific and Technological Cooperation in the Danube Region - 2024"
Period: 11.07.2025 - 11.07.2027
Budget for SU: 49,200 BGN
Project Summary
The transition to sustainable energy requires innovative solutions in renewable energy technologies. High-efficiency photovoltaic (PV) devices are at the forefront of this effort, particularly thanks to tandem structures. Among the key materials being developed for next-generation photovoltaic devices are perovskites and thin III-V films, with both materials showing exceptional optoelectronic properties and promising significant improvement in the performance of future multi-junction solar cells.
Despite their great potential, each of these materials faces critical technological challenges. III-V compound films, known for their superior efficiency and robustness, are still not cost-effective and remain incompatible with large-scale terrestrial deployment, given the high cost of III-V substrates. Among the proposed strategies for cost reduction, some research teams focus on epitaxial growth of III-V materials on more accessible substrates such as silicon.
Meanwhile, perovskites have shown rapid progress and impressive efficiency gains, but issues related to stability, defect control, and ion migration continue to limit their commercial application.
The project brings together the complementary expertise of three leading European laboratories: Laboratoire de Genie electrique et electronique de Paris (GeePs) - photoluminescence, Sofia University "St. Kliment Ohridski" - Surface Photovoltage (SPV), and the Institute of Physics of the Czech Academy of Sciences (FZU) - Photothermal Deflection Spectroscopy (PDS). By combining these techniques, the project aims at a comprehensive understanding of the properties of novel III-V films and perovskite materials.
AFM (C-AFM, KPFM), Raman, XPS/UPS, SSPG, and other advanced methods are also used.
Participants
Sofia University "St. Kliment Ohridski"
Coordinator: Prof. Dr. Veselin Donchev
Email: vtd@phys.uni-sofia.bg
GeePs, CentraleSupelec (France)
Coordinator: Dr. Jose Alvarez
Email: jose.alvarez@centralesupelec.fr
Institute of Physics, Czech Academy of Sciences
Coordinator: Dr. Ledinsky
Email: ledinsky@fzu.cz
Work Packages
| Types of Activities | Executors | Expected Results |
|---|---|---|
|
WP 0. Management and Dissemination 0.1 Project management 0.2 Dissemination of results |
All |
- Interim and final report; - Website; - Participation in international conferences; - Minimum 2 scientific articles in IF journals. |
|
WP 1. Sample Preparation 1.1 Epitaxial III-V layers on GaAs and c-Si 1.2 Preparation of perovskite films |
French team Czech team |
- III-V layers on GaAs and c-Si; - P-N junctions on GaAs and/or c-Si; - stable perovskite structures. |
|
WP 2. Surface Photovoltage (SPV) 2.1 SPV spectra 2.2 SPV transients 2.3 Diffusion length estimation |
Bulgarian team |
- Bandgap energy; - Movement of energy zones at the surface and interface; - Processes of generation, recombination and transport of charge carriers. |
|
WP 3. Photothermal Deflection Spectroscopy (PDS) PDS absorption spectra |
Czech team |
- Optical absorption spectrum; - Defect identification. |
|
WP 4. Photoluminescence (PL) 4.1 Modulated PL 4.2 Transient PL 4.3 Steady-state PL |
French team |
- Carrier dynamics; - Bandgap; - Defect levels. |
|
WP 5. Comparative Characterisation and Modeling 5.1. SPV/PL correlation; 5.2. Comparison of PDS, SSPG, SPV results; 5.3. Comparison of Raman, XPS/UPS results; 5.4. C-AFM, KPFM |
All |
- Better understanding of charge carrier transport; - Information on defect influence; - Structure-properties-stability correlation. |
Results
Publications
- Minimum 2 scientific publications in IF journals.
- Planned joint publications among the three partner institutions.
Participation in Scientific Forums
- IX National Student Scientific Conference "Physics-Engineering-Technologies", 04 - 05 December 2025, Plovdiv https://shorturl.at/KSnrb
- scientific forum 2
Petko Elenkin (oral presentation)
Investigation of GaSb Micro-Islands Deposited on Si Substrates
Abstract:
Gallium antimonide (GaSb), with its direct bandgap of 0.726 eV and room-temperature carrier mobilities around or above 1000 cm2/Vs, is well suited for various optoelectronic applications and is a promising candidate for Si/III-V planar integration. However, depositing GaSb on Si substrates remains technically challenging due to the large lattice mismatch (~12%) and the significant difference (by a factor of ~3) in their thermal expansion coefficients.
Using Ag nano-dots as catalysts and a simple thermal evaporation technique, we have obtained microscopic GaSb islands of high crystalline quality on (100) p-Si substrates. This is supported by structural characterisation reported earlier (AFM, SEM, XRD, Raman scattering).
The present work focuses on the mechanisms of photovoltage generation in these microstructures. A comparison between the surface photovoltage (SPV) spectra of the GaSb/Si sample and pure Si reveals a distinct photovoltage contribution arising from the GaSb islands, with a phase opposite to that observed in pure Si. The possible origin of this inverse-phase SPV signal is discussed.
Working Meetings with Partners
- Working Meeting 1
- Short-term scientific mobility for PhD students and students.
Location: Paris - GeePs, IPVF
Period: 23.11. - 02.12.2025
Participants: representatives of the three partners: GeePs & IPVF, SU, FZU
Current scientific research on the project topic was discussed as follows.
SU presented results from surface photovoltage studies on GaAs/GaAs and GaAs/Ge/Si structures provided by the French partners.
FZU presented results obtained through photoluminescence and photoconductivity on similar samples.
The French team presented results from photoluminescence measurements.
All results were discussed jointly by the three teams. Plans were outlined for what samples the French team should prepare next and what new measurements should be made. In particular, it was decided what new samples the Bulgarian team should receive and what research to focus on in the coming months.
Particularly interesting was the visit to the laboratories of the French Institute of Photovoltaics (IPVF) and part of the laboratories of the Polytechnic School in Paris (Ecole Polytechnique de Paris).
A visit to the Czech laboratory was planned for spring 2026.
With a modeling specialist, we discussed the use of the software package Solcore for calculations of semiconductor structures, including solar cells.