Harnessing the power of the sun and converting it into electricity using photovoltaic solar cells is one of the top contenders for combating the current energy crisis. To this end, researchers have developed organic photovoltaics (OPVs) with transition metal oxide (TMO) thin-film interfacial layers as a cost-effective alternative to commercial silicon solar cells. OPVs are known for their excellent photochemical properties and low-cost mass producibility. However, the TMO layer often suffers from a degraded electrical conductivity owing to the presence of lingering organic metal-binding ligands generated during their synthesis. This greatly limits the OPVs from reaching their full potential.
A team of researchers led by Prof. Kwanghee Lee from Gwangju Institute of Science and Technology, Korea found a way to overcome this challenge. The team demonstrated a simple and effective way of eliminating the residual organic metal-binding ligands from molybdenum oxide (MoO x ) precursor at room temperature using a technique called “anion-induced catalytic reaction” (ACR). This breakthrough was made available online on 25 June 2022 was published in Volume 32, Issue 35 of the journal Advanced Functional Materials on 25 August 2022.
When asked about the rationale behind the study, Prof. Lee says, “ While OPVs with TMO thin films are headed towards power conversion efficiencies as high as 19%, the organic metal-binding ligands left behind the after sol-gel synthesis act like a double-edged sword, helping with the formation of the TMO thin films but deteriorating their properties as well. So, we aimed to find a way to eliminate the unwanted ligands after the synthesis process. ”
Accordingly, the team prepared a TMO thin film using an organic ligand-containing ionic compound and an MoO x -based precursor by introducing ACR alongside the hydrolysis and condensation steps that take place during the sol-gel method. X-ray analysis and density functional theory calculations revealed that ACR induced a strong electrostatic repulsion via low-level anions, which expedited the hydrolysis process and resulted in a quick removal of the organic-metal binding ligands at room temperature.
The team then prepared an inverted OPV configuration using the ACR-derived MoO x thin film to test its electrical properties. To their delight, they observed a 20-fold enhancement in the film’s electrical conductivity along with an excellent work function tunability compared to pristine MoO x . Further, the inverted OPV configuration showed 17.6% improved efficiency, with over 70% retention of the initial efficiency for up to 100 hours.
This novel strategy could not only ensure a superior light-to-electricity conversion efficiency required for commercialization but also enable energy-efficient mass production of next-generation OPV solar cells. “ We strongly believe that the insights provided by our findings will open up new horizons in the production of large-area, wearable, flexible, and printable electronics ,” concludes an optimistic Prof. Lee.
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Reference
DOI: https://doi.org/10.1002/adfm.202204493
Authors: Taeyoon Ki 1,2 , Changhoon Lee 3 , Jehan Kim 4 , In-Wook Hwang 5 , Chang-Mok Oh 5 , Kiyoung Park 1,2 , Sanseong Lee 1,2 , Ju-Hyeon Kim 1,2 , Chandran Balamurugan 1,6 , Jaemin Kong 7 , Hyeon-Seok Jeong 7 , Sooncheol Kwon* 6 ,and Kwanghee Lee* 1,2,7
Affiliations:
1 Heeger Center for Advanced Materials (HCAM)
Gwangju Institute of Science and Technology
2 School of Materials Science and Engineering
3 Max Planck POSTECH Center for Complex Phase of Materials
Pohang University of Science and Technology
4 Pohang Accelerator Laboratory (PAL)
5 Advanced Photonics Research Institute (APRI)
6 Department of Energy and Materials Engineering
Dongguk University-Seoul
7 Research Institute for Solar and Sustainable Energies (RISE)
About the Gwangju Institute of Science and Technology (GIST)
The Gwangju Institute of Science and Technology (GIST) is a research-oriented university situated in Gwangju, South Korea. Founded in 1993, GIST has become one of the most prestigious schools in South Korea. The university aims to create a strong research environment to spur advancements in science and technology and to promote collaboration between international and domestic research programs. With its motto of “A Proud Creator of Future Science and Technology,” GIST has consistently received one of the highest university rankings in Korea.
Website: http://www.gist.ac.kr/
About the author
Kwanghee Lee is a Professor of Materials Science and Engineering at Gwangju Institute of Science and Technology (GIST), Korea and the director of Research Institute for Solar and Sustainable Energies (RISE) at GIST. He received his Ph.D. in physics in 1995 and completed his postdoctoral training at the Institute for Polymers and Organic Solids from UC Santa Barbara in USA in 1997. Prof. Lee’s group is currently working on printing electronics using metallic and semiconducting polymers. Additionally, his research focuses on the development of organic and perovskite solar cells with the highest efficiency. Prof. Lee was awarded the Order of Science and Technology Merit of the Republic of Korea in 2022 for his contributions to science.
Advanced Functional Materials
Experimental study
Not applicable
Anion-Induced Catalytic Reaction in a Solution-Processed Molybdenum Oxide for Efficient Inverted Ternary Organic Photovoltaics
25-Aug-2022
The authors declare no conflict of interest.