| NSF Org: |
DMR Division Of Materials Research |
| Recipient: |
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| Initial Amendment Date: | August 7, 2015 |
| Latest Amendment Date: | August 20, 2017 |
| Award Number: | 1506504 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Tania M. Paskova
DMR Division Of Materials Research MPS Directorate for Mathematical and Physical Sciences |
| Start Date: | August 15, 2015 |
| End Date: | July 31, 2018 (Estimated) |
| Total Intended Award Amount: | $300,000.00 |
| Total Awarded Amount to Date: | $403,833.00 |
| Funds Obligated to Date: |
FY 2016 = $51,759.00 FY 2017 = $52,074.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
845 N PARK AVE RM 538 TUCSON AZ US 85721 (520)626-6000 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Tucson AZ US 85721-0041 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): |
OFFICE OF MULTIDISCIPLINARY AC, DMR SHORT TERM SUPPORT, ELECTRONIC/PHOTONIC MATERIALS, XC-Crosscutting Activities Pro |
| Primary Program Source: |
01001617DB NSF RESEARCH & RELATED ACTIVIT 01001718DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.049 |
ABSTRACT
Nontechnical Description: This project focuses on the characterization and control of the interfaces formed between electrodes and new materials (perovskites) that have shown great promise as active layers in new solar cell platforms. Such platforms have potential as inexpensive, earth-abundant alternatives for production of electricity from sunlight. One of the key challenges in the development of new energy conversion platforms is the understanding and optimization of the transfer of electrical charges between the active layer material and the electrical contacts. This project develops new measurement approaches in order to understand the structure of the active layer near the electrical contact, and how this structure influences electrical properties that ultimately control energy conversion efficiency. The project also provides opportunities for training of graduate students at the University of Arizona and for undergraduate students from the AZ Science, Engineering, and Math Scholars (ASEMS) Program, which focuses on students from minority populations, low-income households, and families where the student is the first to attend college. The co-principal investigators also continue a partnership with Yavapai Community College in Prescott, Arizona - providing "gateway" research experiences for freshman and sophomores.
Technical Description: This project focuses on the nanometer-scale characterization and control of physical, energetic and electrical property heterogeneity, across interfaces between metal halide perovskites, as well as hybrid active layer materials, and electrical contacts. These interfaces are model systems to explore charge collection or injection in emerging thin-film solar energy conversion platforms. The project includes: a) control of interface composition in prototype electrical contacts and charge selective interlayers, using self-assembled monolayers with terminal functional groups that "template" growth of perovskite active layers; b) characterization of valence band energies and energetic dispersion as a function of active layer structure via high-sensitivity UV-photoemission spectroscopies and high-resolution, angle-resolved X-ray photoemission; c) probing conduction band energies in the active layer and dispersion in band edge energies arising from compositional and structural heterogeneity, using waveguide-based spectroelectrochemical techniques; d) characterization of the electrical properties of contact/active layer heterojunctions at 10-100 nm length scales using conducting-tip atomic force microscopy to map heterogeneity in electrical properties. This fundamental study could reveal the charge transfer mechanisms and ultimately lead to efficient energy conversion in the emerging solar cell platforms.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Project Outcomes for NSF DMR 1506504 -- "Characterization and Control of Structure, Energetics and Electrical Properties at Interfaces between Perovskite Active Layers and Charge-Collection Electrodes"
This project focused on the nanometer-scale chemistries that occur when hybrid organic-inorganic perovskite solar cell active layers are deposited on semi-transparent metal oxide thin films (in this case titanium oxide), and how the defects that appear in these oxide layers control the physical and electronic properties of these exciting new active layer materials.
Perovskite materials are an exciting new active layer material for printable thin film solar cells, and since their widespread introduction less than 10 years ago have demonstrated solar energy conversion efficiencies exceeding 20% for small area research cells - an efficiency that rivals that of conventional photovoltaic cells, like silicon. These thin film solar cells have the potential to make a significant impact as a renewable energy source since they can be scaled to large areas at low cost using conventional printing technologies, they can be printed as semi-transparent films for "building integrated photovoltaics" (BIPV), and the can be printed on light weight flexible substrates, attributes that are difficult to attain with conventional semiconductor materials.
Challenges remain, however, in that when these active layers are scaled to large areas, typically printing on metal oxide contacts, their coherence, energy conversion efficiency and stability become problematic, primarily because their chemical and physical interactions with these oxides is not well characterized and controlled.
Our work focused firstly on understanding for the first time the complex chemical reactions that can occur between clean oxide surfaces and these perovskite layers, that wind up controlling their growth and coherence as solar cell active layers. Secondly we developed for the first time new routes to the chemical modification of these oxide layers to mitigate the interactions between the perovskite layers and the reactive defects in the oxide surface - which effectively creates an "innocent surface" for the perovskite, and much more easily controlled growth of coherent films, with stronger electronic coupling to the oxide contact. Testing of device platforms using this new understanding of these interfaces is underway, both to determine if high efficiencies can be achieved for energy conversion, for large area solar cells, and to see if overall device stability is enhanced.
Last Modified: 10/02/2018
Modified by: Neal R Armstrong
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