Chung-Ang University study reveals a way to enhance the efficiency of perovskite solar cells

Solar energy is one of humanity’s best bets against the ongoing energy crises and climate change. With solar panels becoming an attractive energy solution, both in open fields and on rooftops in urban areas, scientists are diligently working to advance existing photovoltaic technologies and achieve new heights in sustainability. While many types of photovoltaic materials are being studied, perovskites are undoubtedly among the most promising due to their potential for low-cost production and higher efficiency.

In particular, tin halide perovskites (Sn-HPs) serve as powerful alternatives to the exceptionally high-performing lead (Pb)-based perovskites. Given that Sn is significantly less toxic to the environment than Pb, research into Sn-HPs is a worthwhile endeavor. Unfortunately, perovskite solar cells (PSCs) made from Sn-HPs still face several challenges that need to be addressed. Specifically, the rapid and disordered crystallization during production leads to the formation of defects in the crystal structure of the perovskite layer, which hampers conversion efficiency. Additionally, Sn-HPs suffer from low stability and high sensitivity to moisture and ambient conditions, limiting the overall lifetime of PSCs made from them.

Now, however, a research team from Korea may have found an elegant and efficient solution to these issues. Their study was recently published in Advanced Energy Materials and was led by Associate Professor Dong-Won Kang from Chung-Ang University. In this study, the team revealed that introducing 4-Phenylthiosemicarbazide (4PTSC) as an additive during the production of Sn-HPs can boost the performance of PSCs. Their findings were made available online on April 10, 2024, and published in Volume 14, Issue 25 of the journal on July 5, 2024.

Through extensive analyses and experimental comparisons between regular Sn-HP PSCs and those containing the proposed additive, the researchers showcased the multiple functionalities of 4PTSC as an additive. "We purposely chose a multifunctional molecule that acts as a coordination complex and a reducing agent, passivates defect formation, and improves stability," explains Kang. But what does this mean?

Since 4PTSC functions as a coordinating ligand, it can effectively regulate the process of crystal growth. On the one hand, the π-conjugated phenyl ring in the 4PTSC molecule promotes preferred crystal growth orientation, minimizing the formation of defects. Interestingly, 4PTSC also passivates any defects that do form through the chemical coordination of 4PTSC and SnI₂. In turn, this shields the perovskite surface and prevents uncoordinated Sn²⁺ and halide ions from participating in unwanted reactions. What's more, the –NH₂ nucleophilic sites in 4PTSC further hinder SnI₂ oxidation and ion migration, improving the stability of the PSCs.

Thanks to this powerful additive, the researchers were able to produce PSCs with unprecedented performance. "The 4PTSC-modified devices achieved a peak efficiency of 12.22% with an enhanced open-circuit voltage of 0.94 V and exhibited superior long-term stability, retaining almost 100% of the initial power conversion efficiency, even after 500 h and about 80% after 1200 h in ambient conditions without any encapsulation. This is different from the marked degradation observed in control devices within the first 300 h," highlights Kang.

Given that Sn-HPs are relatively inexpensive to manufacture and demonstrate good performance and great durability, the findings of this study could pave the way to more accessible and long-lasting solar panels. In turn, this can help in making energy cheaper for the general population while staying in line with current sustainability goals. "Addressing the key challenges of Sn-HPs and significantly improving their performance aligns with our goal of contributing to developing efficient and sustainable renewable energy solutions, thereby advancing green technologies and promoting a sustainable future," concludes Kang.

Let us hope further efforts in this growing research field lead to a revolution in how we generate clean energy.

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Reference                                                                                             

Authors: Padmini Pandey¹, SungWon Cho², Jitendra Bahadur¹, Saemon Yoon², Chang-Mok Oh³, In-Wook Hwang³, Hochan Song⁴, Hyosung Choi⁴, Shuzi Hayase^5,6, Jung Sang Cho⁷, and Dong-Won Kang^1,2

Title of original paper: 4-Phenylthiosemicarbazide Molecular Additive Engineering for Wide-Bandgap Sn Halide Perovskite Solar Cells with a Record Efficiency Over 12.2%

Journal: Advanced Energy Materials

DOI: https://doi.org/10.1002/aenm.202401188

Affiliations:

¹Department of Energy Systems Engineering, Chung-Ang University, Republic of Korea

²Department of Smart Cities, Chung-Ang University, Republic of Korea

³Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Republic of Korea

⁴Department of Chemistry, Research Institute for Convergence of Basic Science, Research Institute for Natural Sciences, Hanyang University, Republic of Korea

⁵i-Powered Energy System Research Center (i-PERC), The University of Electro-Communications, Republic of Korea

⁶Graduate School of Informatics and Engineering, The University of Electro-Communications, Republic of Korea

⁷Department of Engineering Chemistry, Chungbuk National University, Republic of Korea

About Chung-Ang University

Chung-Ang University is a private comprehensive research university located in Seoul, South Korea. It was started as a kindergarten in 1916 and attained university status in 1953. It is fully accredited by the Ministry of Education of Korea. Chung-Ang University conducts research activities under the slogan of “Justice and Truth.” Its new vision for completing 100 years is “The Global Creative Leader.” Chung-Ang University offers undergraduate, postgraduate, and doctoral programs, which encompass a law school, management program, and medical school; it has 16 undergraduate and graduate schools each. Chung-Ang University’s culture and arts programs are considered the best in Korea.

Website: https://neweng.cau.ac.kr/index.do

About the author

Dong-Won Kang is an Associate Professor of the School of Energy Systems Engineering at Chung-Ang University, Seoul, Republic of Korea. He obtained his Ph.D. in Electrical Engineering and Computer Science from Seoul National University in 2013. Following this, he worked as a postdoctoral researcher at the Tokyo Institute of Technology. In 2015, he joined Cheongju University as an Assistant Professor and has been at Chung-Ang University since 2018. His research group is actively involved in developing single and multi-junction perovskite solar cells and designing new photo-absorbers with super narrow bandgaps to harness low-energy photons efficiently. Kang's group is also developing translucent-wearable solar modules and solar-battery-integrated devices.

Website: https://scholarworks.bwise.kr/cau/researcher-profile?ep=1080