© Adrian RADU 2007
 
Project: PN-III-P1-1.1-TE-2019-0846
Grant number: 25/2020
Funding Agency: UEFISCDI, Romania
Title: Nanoimprint lithography for photovoltaic devices
Budget: 431.000 lei
Grant period: 24 months, from 15.09.2020 to 14.09.2022
Coordinator: University of Bucharest
Director of the project: Assoc. Prof. Sorina Iftimie, PhD
Contact: sorina.iftimie@fizica.unibuc.ro


Abstract:
This proposal introduces the use of nanoimprint lithography (NIL) for the development of photovoltaic devices based on cadmium telluride (CdTe) as absorber. Our innovative design assumes that CdTe nanopillars (CdTe nnp) with dimensions of 500 nm x 500 nm and 700 nm x 700 nm will be prepared by NIL and electrochemical deposition, leading to an entirely nanostructured absorber. The heterojunction will be completed either by cadmium sulfide (CdS), zinc sulfide (ZnS), and zinc selenide (ZnSe), as window layers, deposited by radio frequency magnetron sputtering. As back electrode, copper (Cu) and gold (Au) co-evaporated thin films will be used, while the transparent electrode will be obtained by radio frequency magnetron sputtering from indium tin oxide (ITO).
The specific objectives of this proposal are:
Ob1. The fabrication and complete characterization of constitutive and Cu:Au/CdTe nanopillars/CdS/ITO photovoltaic device
Ob2. The fabrication and complete characterization of constitutive and Cu:Au/CdTe nanopillars/ZnS/ITO photovoltaic device
Ob3. The fabrication and complete characterization of constitutive and Cu:Au/CdTe nanopillars/ZnSe/ITO photovoltaic device
The chosen of these materials was motivated by the very good results obtained for AIIBVI heterojunction, in planar configuration, and the good compatibility between CdTe as absorber and CdS, ZnS, and ZnSe as window layer, on one hand, and on the other by the extensive expertise of project leader in the research area of photovoltaic devices based on inorganic materials. Moreover, due to nanostructuring, the active area surface will be considerably increased and the photo-electric processes at the p-n interface will be improved, as so the overall performance of the device.
We admit that at the end of this project an innovative working routine of development of photovoltaic structures will be delivered together with complete reports describing the physical properties of customized devices and their components.


Research team:
  1. Assoc. Prof. Sorina Iftimie, PhD - director of the project
  2. Senior Researcher Oana Raşoga
  3. Assoc. Prof. Vlad-Andrei Antohe, PhD
  4. PhD student Claudiu Locovei
  5. PhD student Ana-Maria Răduţă
  6. Professor Ştefan Antohe, PhD


The main goals of the project are:
Ob1. The development and complete characterization of constitutive and Cu:Au/CdTe nanopillars/CdS/ITO photovoltaic device
Ob2. The development and complete characterization of constitutive and Cu:Au/CdTe nanopillars/ZnS/ITO photovoltaic device
Ob3. The development and complete characterization of constitutive and Cu:Au/CdTe nanopillars/ZnSe/ITO photovoltaic device.


The most important results and their impact on the field of Materials Science
Photovoltaic devices based on an innovative architecture of the active film, namely CdTe_nanopillars, have been fabricated by nano-imprint lithography - UV exposure. Through this project, we have demonstrated that the active area can be significantly enlarged by building a totally nanostructured absorber layer, with a highly orderly configuration. Nanopillars of conic shape, with a high of 850 nm and a distance between their exterior edges of 750 nm were fabricated from cadmium telluride (CdTe), while the window layer was either CdS, ZnS, or ZnSe.
The photo-electrical analysis proved that such an ingenious structure, obtained by relatively low-cost techniques, opens new doors in the field of Photovoltaics and Materials Science. We admit that the optimization procedures, even for common-used materials, need further and focused studies.


Results and dissemination
A. Articles
  1. M. Panaitescu, I. Antohe, C. Locovei, S. Iftimie, S. Antohe, L. Piraux, M.P. Suchea, V.A. Antohe, Effect of the cadmium telluride deposition method on the covering degree of electrodes based on copper nanowire arrays, Applied Sciences - Basel 12, 7808 (2022).
  2. I. Radu, V.A. Antohe, S. Iftimie, I. Antohe, M. Filipescu, A. Radu, D. Coman, M.L. Stîngescu, M. Dinescu, S. Antohe, Study of a new composite based on SnO2 nanoparticles - P3HT:PC71BM co-polymer blend, used as potential absorber in bulk heterojunction photovoltaic cells, submitted to Materials Today Communications.
  3. Physical properties of RF-sputtered ZnSe thin films for photovoltaic applications: influence of film thickness, L. Ion, S. Iftimie, A. Radu, V.A. Antohe, O. Toma, S. Antohe, Proceedings of the Romanian Academy Series A - Mathematics Physics Sciences Information Science 22, 25-34, 2021.
  4. Thickness effect on some physical properties of RF sputtered ZnTe thin films for potential photovoltaic applications, D. Manica, V.A. Antohe, A. Moldovan, R. Pascu, S. Iftimie, L. Ion, M.P. Suchea, S. Antohe, Nanomaterials 11, 2286, 2021.
B. National and international conferences
  1. S. Iftimie, A.M. Raduta, A.M. Panaitescu, I. Radulian, C. Locovei, V.A. Antohe, A. Radu, L. Ion, S. Antohe, On the photovoltaic performances of CdTe/CdS heterojunction-based devices - the effect of the transparent electrode, EMRS Spring Meeting 2022, online event, 30.05 - 03.06.2022.
  2. Effects of in-situ and ex-situ thermal annealing on the physical properties of RF sputtered indium thin oxide thin films, S. Iftimie, D. Coman, C. Locovei, A. Radu, V.A. Antohe, A. Dumitru, M. Manica, C. Radu, L. Ion, and S. Antohe, EMRS Spring Meeting 2021, online event, 31. 05. - 04.06.2021.
  3. A comparison between substrate and superstrate photovoltaic structures based on CdTe/CdS heterojunction, S. Iftimie, C. Locovei, A.G. Sovaiala, O.D. Baban, A.M. Raduta, A.M. Panaitescu, A. Radu, V.A. Antohe, A. Dumitru, L. Ion, and S. Antohe, EMRS Spring Meeting 2021, online event, 31. 05. - 04.06.2021.
  4. Effect of the applied power on the structural, morphological, optical and electrical properties of RF-sputtered ZnSe thin films, A.M. Panaitescu, O. Toma, S. Iftimie, A. Radu, A.M. Raduta, D. Manica, L. Dan, L. Ion, S. Antohe, V.A. Antohe, EMRS Spring Meeting 2021, online event, 31. 05. - 04.06.2021.
  5. Physical properties of ultra-thin heterojunctions based on Cd and Cd free AII-BVI compounds for electronic and optoelectronic applications, A.M. Panaitescu, A.M. Raduta, V.A. Antohe, S. Iftimie, A. Radu, L. Ion, S. Antohe, TIM 20-21 Physics Conference, online event, 11.11. - 13.11.2021.