Hybrid heterojunction solar cells using single-walled carbon nanotubes and amorphous silicon thin films

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School of Science | Doctoral thesis (article-based) | Defence date: 2020-05-27
Degree programme
76 + app. 67
Aalto University publication series DOCTORAL DISSERTATIONS, 79/2020
Single-walled carbon nanotubes possess extraordinary optical, electrical, chemical, and mechanical properties. Thin films of randomly oriented SWCNTs have a great potential in many opto-electro-mechanical applications. Moreover, recent developments in photovoltaics have been largely contributed by SWCNTs as a p-type transparent conductor that fulfill the requirements for continuous, fast, and cheap film manufacturing process compatible with the roll-to-roll technology.  The scope of this thesis is the development of a conductive p-type SWCNT transparent conductor and its application in hybrid heterostructure solar cell based on amorphous silicon. For successful implementation of SWCNTs film in solar cells, it is very critical for the SWCNTs to have good physical contact with the material on which it is deposited. At first, quantitative measurements of the adhesion of SWCNT films with substrate materials in air and inert Ar atmosphere using atomic force microscopy was performed. It was found that adhesion of SWCNT films depends on the atmospheric conditions under which it is stored and deposited on a substrate material. The SWCNT film was measured to have higher adhesion in an inert atmosphere. With this understanding, a simple fabrication method of hybrid heterostructure solar cells was proposed in which the SWCNT-PEDOT:PSS composite p-type film forms a coupled continuous hybrid heterojunction with a-Si:H absorber. The optical and electrical properties of this composite was extensively characterized and further optimized by introducing multifunctional components like ultrathin MoO3 and SWCNT fibers. A rationally designed p-type transparent conductor with a combination of SWCNTs-MoO3-PEDOT:PSS-SWCNT fibers composite resulted in a state-of-the-art sheet resistance of 17 Ω/sq at 90% transmittance. Moreover, SWCNT fibers by itself can be used as replacement for traditional metal contacts as demonstrated here. This opens a new avenue in widespread energy technologies, where high hole conductivity and transparency of the material are prerequisites for their successful implementation.  Integrating the developed p-type transparent conductor as a window layer and top electrode on a-Si:H in a nip configuration resulted in a dramatic increase in its power conversion efficiency reaching up to 8.8%. The energy level alignment of these solar cells is carefully engineered at a-Si:H and SWCNTs interface by introducing a ultrathin MoO3 layer that shows the carrier transport by means of band-to-band or trap-assisted tunneling.
The doctoral dissertation is conducted under a convention for the joint supervision of thesis at Aalto University (Finland) and Skolkovo Institute of Science and Technology (Russia) for the degree of Doctor of Science (Technology) at Aalto University.
The public defense on 27th May 2020 at 17:00 (5 p.m.) will be organized via remote technology. Link: https://aalto.zoom.us/j/63096711658 Zoom Quick Guide: https://www.aalto.fi/en/services/zoom-quick-guide
Supervising professor
Lund, Peter D., Prof., Aalto University, Department of Applied Physics, Finland
Nasibulin, Albert G., Prof., Skolkovo Institute of Science and Technology, Russia
single-walled carbon nanotubes, amorphous silicon, hybrid, heterojunction, thin, films, solar cells
Other note
  • [Publication 1]: Pramod M. Rajanna, Sergey Luchkin, Konstantin V. Larionov, Artem Grebenko, Zakhar I. Popov, Pavel B. Sorokin, Mati Danilson, Sergei Bereznev, Peter D. Lund, and Albert G. Nasibulin. Adhesion of Single-Walled Carbon Nanotube Thin Films with Different Materials. J. Phys. Chem. Lett. 2020, 11, 504−509.
    DOI: 10.1021/acs.jpclett.9b03552 View at publisher
  • [Publication 2]: Pramod M Rajanna, Evgenia P Gilshteyn, Timur Yagafarov, Alena K Aleekseeva, Anton S Anisimov, Alex Neumüller, Oleg Sergeev, Sergei Bereznev, Jelena Maricheva, and Albert G Nasibulin. Enhanced efficiency of hybrid amorphous silicon solar cells based on single-walled carbon nanotubes and polymer composite thin film. Nanotechnology 29 (2018) 105404 (10 pp).
    DOI: 10.1088/1361-6528/aaa647 View at publisher
  • [Publication 3]: Alena K. Alekseeva, Pramod Mulbagal Rajanna, Anton S. Anisimov, Oleg Sergeev, Sergei Bereznev, and Albert G. Nasibulin. Synergistic Effect of Single-Walled Carbon Nanotubes and PEDOT:PSS in Thin Film Amorphous Silicon Hybrid Solar Cell. Phys. Status Solidi B 2018, 255, 1700557.
    DOI: 10.1002/pssb.201700557 View at publisher
  • [Publication 4]: Pramod M. Rajanna, Hosni Meddeb, Oleg Sergeev, Alexey P. Tsapenko, Sergei Bereznev, Martin Vehse, Olga Volobujeva, Mati Danilson, Peter D. Lund, Albert G. Nasibulin. Rational design of highly efficient flexible and transparent p-type composite electrode based on single-walled carbon nanotubes. Nano Energy 67 (2020) 104183.
    DOI: 10.1016/j.nanoen.2019.104183 View at publisher
  • [Publication 5]: Pramod M. Rajanna, Peter D. Lund, Albert G. Nasibulin. Hybrid hetero-junction solar cells based on single-walled carbon nanotubes and amorphous silicon thin film - a mini review. Submitted, May 2020.