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Vertically aligned Co3O4 nanorods as a platform for inverted all‐oxide heterojunctions
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0002-3956-444X
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0001-6039-1865
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0001-7475-6394
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0001-8889-4157
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2021 (English)In: Nano Select, E-ISSN 2688-4011, Vol. 2, no 5, p. 967-978Article in journal (Refereed) Published
Abstract [en]

Direct stacking of n‐type and p‐type metal oxide (MOx) semiconductors is one of the appealing directions toward low cost and environmentally friendly photovoltaics (PVs). However, the main shortcoming, hindering the PV performance of MOx heterojunction devices is attributed to the tradeoff between light absorption and maximized carrier extraction in p‐type MOx. In this work, we demonstrate that the nanorod (NR) geometry of Co3O4 light absorber with a nearly ideal bandgap of ∼1.48 eV, can remove this hurdle through strong internal light trapping of adjacent one‐dimensional (1D) structure and enhanced carrier mobility. The inverted n‐on‐p configuration of the core‐shell 1D heterojunction, obtained by depositing a thin TiO2 n‐type layer, resulted in enlarged charge generation compared to the typical p‐on‐n counterpart device. Fine‐tuning of Co3O4 NRs length, permits PV investigation of the heterojunctions with respect to absorber layers thickness. The optimized Co3O4 NRs/TiO2 heterojunction (30 nm Co3O4 NR length) presented a record high open circuit photovoltage (Voc) of (0.52 ± 0.03) V under 1 sun irradiation. Impedance analysis of the heterojunctions, indicates formation of the p+‐p depletion. The presented work can highlight some vital venues to enhance photoconversion efficiency of the all‐oxide heterojunctions while introducing a pioneer contender as inverted (n‐on‐p) MOx heterojunction.

Place, publisher, year, edition, pages
John Wiley & Sons, 2021. Vol. 2, no 5, p. 967-978
Keywords [en]
all‐oxide solar cell, cobalt oxide nanorods, core‐shell nanorods, inverted heterojunction
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
URN: urn:nbn:se:ltu:diva-82468DOI: 10.1002/nano.202000252OAI: oai:DiVA.org:ltu-82468DiVA, id: diva2:1519007
Funder
Swedish Research CouncilLuleå University of TechnologyThe Kempe FoundationsEU, Horizon 2020, 654002Knut and Alice Wallenberg FoundationVinnova
Note

Godkänd;2021;Nivå 0;2021-07-13 (johcin)

Available from: 2021-01-18 Created: 2021-01-18 Last updated: 2021-10-15Bibliographically approved
In thesis
1. Alternative Energy Harvesting and Conversion Systems Based on Nanostructured Heterostructures
Open this publication in new window or tab >>Alternative Energy Harvesting and Conversion Systems Based on Nanostructured Heterostructures
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Conversion and storage of the solar radiation into applicable forms of energy, using ubiquitous materials is of central importance that quests several disciplinary fields in both applied technology and fundamental science. Harnessing the solar energy received by the earth has the potential to replace the current sources of energy and it is imperative for sustainable development. 

Since the early development of modern photovoltaics (PVs), based on silicon wafers, a rational step was the substantial development of the new generation PV technologies that can provide lower-cost and higher efficiency than their predecessors. Deliberate solutions involved employing different semiconducting materials that are indispensable, non-toxic and compatible with large-scale fabricating technologies.  

Exploiting metal oxide (MOx) semiconductors, a broad class of non-toxic, cheap and abundant materials, is already promoted as a key component for high-performance optoelectronic devices and can be an ideal solution for inexpensive harnessing of sustainable energy resources like Sun light. The favorable band gap and high absorption cross-section of some MOx semiconductors permit utilizing different spectral region of the solar spectrum. However, at this present, the implication of MOx in high-throughput optoelectronic devices remained on the low side. Some of the main drawbacks that attain to poor performance of the MOx are associated with their poor intrinsic carrier mobility especially in p-type light absorbers and insufficient visible light absorption notably in n-type semiconductors.   

The main aim of this thesis is to further contribute to the development and exploitation of this class of materials with the main focus on their role in optoelectronic devices and energy storage systems. 

The content of this thesis considers two main aspect of the research. 

Substantially, this work analyses the vital role of the interface engineering using nanostructured MOx, where we exploit unique phenomena such as intense electric field confinement in 1dimensional (1D) structures resulting in ample light trapping in the fabricated heterojunctions. Unfortunately, this fact comes at the cost of introducing space charge region (SCR) limits in the fabricated devices attaining for poor derived currents. 

Here I would probably spend couple of words for introducing the Co3O4 NR as the basis for p-n inverted nanorod junction…

Plasmonic metal nanoparticles (NPs) were conventionally used to extend the spectral response of the wide-bandgap semiconductors. Within the scheme of this thesis, we employ the silver plasmonic NPs in a 1D light harvesting structure of zinc oxide (ZnO), where we mediate hot-carrier collection of the charges via controlled illuminations. 

Even further, we provide a comprehensive analysis on the hot-carrier redistribution mechanisms of the plasmonic NPs to semiconductor, providing direct experimental proof using transient pump-probe spectroscopy and time-resolved photoluminescence analysis. Our work resulted in a distinct understanding of the radiative and non-radiative carrier transfer between the active constituents of the system, which have not been corroborated previously.

In a parallel approach, the research activities in this work, take a few steps ahead and investigates the issues related to the disparities in the PV plants. A common prerequisite after conversion of the solar light using PV devices is the electrochemical storage of the energy where it can answer the needs for far-reaching energy requirements. Fostered by the intrinsic capacitance characteristic of the MOx, we interplay the role of the interfacial engineering in Co3O4 porous films and investigate the effect of their lateral architecture on Li+ ion adsorption and desorption properties.

Finally, our findings resulted in the fabrication of a hybrid device with dual functionality as an all-oxide PV system that can directly store the converted Sunlight as in a supercapacitor device. The prospect of this device can provide the over-potential required for direct storage of the converted solar energy into larger high storage systems.

In summary, the results presented in this thesis highlights the potential of the MOx semiconductors for photovoltaic and storage applications. We identify the various step-forward routes, which can provide the possibility of large-scale deployment of this novel class of materials.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2021
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
light harvesting, solar supercapacitors, energy conversion, Photovoltaic, energy storage, metal oxide semiconductors
National Category
Nano Technology
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-86691 (URN)978-91-7790-906-4 (ISBN)978-91-7790-907-1 (ISBN)
Public defence
2021-10-05, E632, Luleå, 13:00 (English)
Opponent
Supervisors
Available from: 2021-08-17 Created: 2021-08-17 Last updated: 2021-10-15Bibliographically approved

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Gilzad Kohan, MojtabaSolomon, GetachewYou, ShujieYusupov, KhabibConcina, IsabellaVomiero, Alberto

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