FY2019 Annual Report

Energy Materials and Surface Sciences Unit

 

Abstract

Identification of new properties in novel materials is key for generating new technologies. For example, the fundamental understanding of well-established inorganic or organic materials led to dramatic improvements in the history of technology. Inorganic silicon-based technology enabled unprecedented development of advanced electronic devices (e.g. laptops, smart phones, digital cameras, Si solar cells, etc.). Organic semiconductors on the other hand have received attention in lightweight, flexible, flat-panel-display and organic LED applications. In our unit, we aim at the fundamental understanding of structure-property relationship in energy materials and develop innovative methodologies and devices for the next-generation energy harvesting and storage devices, light emitting systems, and industrially critical gas-separation systems.

During this year, we organized two international symposiums:

Symposium Co-organizer
2018 MRS Spring Meeting - Symposium ES15, “Fundamental Understanding of the Multifaceted Optoelectronic Properties of Halide Perovskites”
Phoenix, Arizona, USA
April 22 - 26, 2019.

Symposium Co-organizer
2019 MRS Fall Meeting - Symposium EN08, “Halide Perovskites for Photovoltaic Applications—Devices, Stability and Upscaling”
Boston, Massachusetts, USA
December 1 - 6, 2019.

1. Unit Members

• Ms. Naoko Ogura-Gayler, Research Unit Administrator
• Dr. Luis K. Ono, Group Leader
• Dr. Longbin Qiu, Researcher
• Dr. Sisi He, Researcher
• Dr. Dae-Yong-Son, Researcher
• Dr. Zhanhao Hu, Researcher
• Dr. Zhifang Wu, Researcher
• Dr. Jeremy Hieulle, Researcher
• Dr. Guoqing Tong, Researcher
• Dr. Maowei Jiang, Researcher
• Dr. Hui Zhang, Researcher
• Dr. Yuiqiang Liu, Researcher
• Dr. Zafer Hawash, OIST Graduate Student
• Mr. Collin C. Stecker, OIST Graduate Student
• Ms. Afshan Jamshaid, OIST Graduate Student
• Ms. Ainash Garifullina, Rotation Student

2. Collaborations

  1. Thermodynamically stabilized β-CsPbI3 - Science 365, 591-595 (2019).
    • Type of collaboration: collaborative research
    • Collaborators:
      • Prof. Yixin Zhao, Shanghai Jiao Tong University, China
      • Prof. Michael Grätzel, Ecole Polytechnique Federale de Lausanne, Switzerland
  2. Lead-free, all-inorganic Ge-based perovskite - Nat. Commun. 10, 16 (2019).
    • Type of collaboration: collaborative research
    • Collaborators:
      • Prof. Yuanyuan Zhou, Brown University, USA.
      • Prof. Nitin P. Padture, Brown University, USA.
  3. THz absorption studies on perovskites - Sci. Rep. 9, 5811 (2019).
    • Type of collaboration: collaborative research
    • Collaborators:
      • Prof. Min-Cherl Jung, Nara Institute of Science and Technology, Japan.
      • Prof. Masakazu Nakamura, Nara Institute of Science and Technology, Japan.

3. Activities and Findings

3.1 Reviews on development of stable and scalable perovskite solar cells/modules and progress of surface science studies on perovskite solar cells.

Luis K. Ono, Shengzhong (Frank) Liu*, and Yabing Qi*, "Reducing Detrimental Defects for High-Performance Metal Halide Perovskite Solar Cells" Angew. Chem. Int. Ed. 59, 2-25 (2020). 

Longbin Qiu†, Sisi He†, Luis K Ono†, Shengzhong (Frank) Liu*, Yabing Qi*, "Scalable Fabrication of Metal Halide Perovskite Solar Cells and Modules" ACS Energy Lett. 4, 2147-2167  (2019). († equal contribution) 

Guoqing Tong†, Luis K. Ono† and Yabing Qi*, "Recent progress of all bromide inorganic perovskite solar cells" Energy Technology 1900961 (2019). († equal contribution) 

 Longbin Qiu†, Sisi He†, Luis K. Ono† and Yabing Qi*, "Progress of Surface Science Studies on ABX3-Based Metal Halide Perovskite Solar Cells" Adv. Energy Mater. 1902726, (2019). († equal contribution)

Zonghao Liu†, Luis K. Ono†, and Yabing Qi*, "Additives in metal halide perovskite films and their applications in solar cells" J. Energy Chem. 46, 215-228 (2020). († equal contribution) 

Sisi He†, Longbin Qiu†, Luis K. Ono†, Yabing Qi*, "How far are we from attaining 10-year lifetime for metal halide perovskite solar cells?" Mater. Sci. Eng. R 140, 100545 (2020). († equal contribution)

Scalability and stability are two critical obstacles for future commercialization of perovskite solar cell technology. To find efficent ways solving the stability problem, we reviewed the present status of perovskite solar cell research  and studied the fundamental degradation mechanisms of perovskite solar cells through advanced surface science technologies at the same time. For the scalability of PSCs, we share our view regarding the currentstage challenges for the fabrication of perovskite solar modules with areas greater than 200 cm2, summarize recent progress in minimizing the efficiency gap, and highlight what strategies warrant further investigation for moving perovskite PV technology toward industrial scale. These strategies include learning from other commercialized thin-film PV technologies, analyzing the current status of perovskite solar modules employing solution- and vapor-based scalable fabrication techniques, and optimizing large-area module designs. Considering cost analysis and operational stability profiles, carbon electrode-based devices are particularly promising.

 

Figure 1: (Left top one) Reviews the scalable fabrication of metal halide perovskite solar cells and modules. (Right top one) Reviews the progress of surface science studies on ABX3-based metal halide perovskite solar cells. (Bottom one) Reviews the stability of metal halide perovskite solar cells.

3.2  Atomic-structural study of perovskite and further exploration of defect dynamics.

Collin Stecker†, Kexi Liu†, Jeremy Hieulle, Robin Ohmann, Zhenyu Liu, Luis K. Ono, Guofeng Wang* and Yabing Qi*, "Surface Defect Dynamics in Organic-Inorganic Hybrid Perovskites: From Mechanism to Interfacial Properties" ACS Nano 13, 12127-12136 (2019). († equal contribution) 

Jeremy Hieulle†, Shulin Luo†, Dae-Yong Son, Afshan Jamshaid, Collin Stecker, Zonghao Liu, Guangren Na, Dongwen Yang, Robin Ohman, Luis K. Ono, Lijun Zhang* and Yabing Qi*, "Imaging of the Atomatic Structure of All-inorganic halide perovskites" J. Phys. Chem. Lett. 11, 818-823 (2020). († equal contribution)

Organic−inorganic hybrid perovskites (OHPs) have garnered much attention among the photovoltaic and light-emitting diode research community due to their excellent optoelectronic properties and low-cost fabrication. Defects in perovskites have been proposed to affect device efficiency and stability and to have a potential role in enabling ion migration. In this study, the dynamic behavior and electronic properties of intrinsic defects in CH3NH3PbBr3 (MAPbBr3) were explored at the atomic scale. We use scanning tunneling microscopy to show unambiguously the occurrence of vacancy-assisted transport of individual ions as well as the existence of vacancy defect clusters at the OHP surface. We combine these observations with density functional theory (DFT) calculations to identify the mechanisms for this ion motion and show that ion transport energy barriers, as well as transport mechanisms, at the surface depend on crystal direction. DFT calculations also reveal that vacancy defect clusters can significantly modify the local work function of the perovskite surface, which is then expected to alter interfacial charge transport in a device. Our work provides a microscopic insight into the mechanism of ion migration in OHPs and also delivers the useful information for device improvement from the perspective of interface engineering.

All-inorganic halide perovskites are promising materials for optoelectronic applications. The surface or interface structure of the perovskites plays a crucial role in determining the optoelectronic conversion efficiency, as well as the material stability. A thorough understanding of surface atomic structures of the inorganic perovskites and their contributions to their optoelectronic properties and stability is lacking. Here we show a scanning tunneling microscopy investigation on the atomic and electronic structure of CsPbBr3 perovskite. Two different surface structures with a stripe and an armchair domain are identified, which originates from a complex interplay between Cs cations and Br anions. Our findings are further supported and correlated with density functional theory calculations and photoemission spectroscopy measurements. The stability evaluation of photovoltaic devices indicates a higher stability for CsPbBr3 in comparison with MAPbBr3, which is closely related to the low volatility of Cs from the perovskite surface.

 

Figure 2: (Left) Surface defect dynamics in MAPbBr3. (Right) Atomic structure of CsPbBr3.

3.3 Thermodynamically stabilized β-CsPbI3-based perovskite solar cells with efficiencies ＞18%.

Yong Wang, M. Ibrahim Dar*, Luis K. Ono, Taiyang Zhang, Miao Kan, Yawen Li, Lijun Zhang, Xingtao Wang, Yingguo Yang, Xingyu Gao, Yabing Qi*, Michael Grätzel*, Yixin Zhao*, "Thermodynamically stabilized β-CsPbI3–based perovskite solar cells with efficiencies >18%" Science 365, 591-595 (2019).

Although β-CsPbI3 has a bandgap favorable for application in tandem solar cells, depositing and stabilizing β-CsPbI3 experimentally has remained a challenge.We obtained highly crystalline β-CsPbI3 films with an extended spectral response and enhanced phase stability. Synchrotron-based x-ray scattering revealed the presence of highly oriented β-CsPbI3 grains, and sensitive elemental analyses—including inductively coupled plasma mass spectrometry and time-of-flight secondary ion mass spectrometry—confirmed their all-inorganic composition. We further mitigated the effects of cracks and pinholes in the perovskite layer by surface treating with choline iodide, which increased the charge-carrier lifetime and improved the energy-level alignment between the β-CsPbI3 absorber layer and carrier-selective contacts. The perovskite solar cells made from the treated material have highly reproducible and stable efficiencies reaching 18.4% under 45 ± 5°C ambient conditions.

Figure 3: Effect of crack-filling interface engineering treatment on the energy-level alignment.

3.4 Reduction of lead leakage from damaged lead halide perovskite solar modules using self-healing polymer-based encapsulation.

Yan Jiang†, Longbin Qiu†, Emilio J. Juarez-Perez, Luis K. Ono, Zhanhao Hu, Zonghao Liu, Zhifang Wu, Lingqiang Meng, Qijing Wang, and Yabing Qi*, "Reduction of lead leakage from damaged lead halide perovskite solar modules using self-healing polymer-based encapsulation" Nat. Energy 4, 585–593 (2019). († equal contribution) 

In recent years, the major factors that determine commercialization of perovskite photovoltaic technology have been shifting from solar cell performance to stability, reproducibility, device upscaling and the prevention of lead (Pb) leakage from the module over the device service life. Here we simulate a realistic scenario in which perovskite modules with different encapsulation methods are mechanically damaged by a hail impact (modified FM 44787 standard) and quantitatively measure the Pb leakage rates under a variety of weather conditions. We demonstrate that the encapsulation method based on an epoxy resin reduces the Pb leakage rate by a factor of 375 compared with the encapsulation method based on a glass cover with an ultraviolet-cured resin at the module edges. The greater Pb leakage reduction of the epoxy resin encapsulation is associated with its optimal self-healing characteristics under the operating conditions and with its increased mechanical strength. These findings strongly suggest that perovskite photovoltaic products can be deployed with minimal Pb leakage if appropriate encapsulation is employed.

Figure 4: Assessment of Pb leakage from damaged perovskite solar modules.

4. Publications

4.1 Journals

    →Please see our publications page for published journals

4.2 Books and Other One-Time Publications

N/A

4.3 Oral and Poster Presentations

  • Yabing Qi, “Degradation Mechanisms of Lead Halide Perovskite Solar Cells and Stability Improvement Strategies", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019. (Invited talk)
  • Jeremy Hieulle, “Unraveling the Impact of Halide Mixing on Perovskite Stability via Scanning Tunneling Microscopy and Photoelectron Spectroscopy", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019.
  • Jeremy Hieulle, “Elucidate the Influence of Cl- and I-Incorporation on the Electronic Properties and Stability of Perovskite Materials", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019.
  • Jeremy Hieulle, “Revealing Cations Locations and their Impact on the Properties of Mixed MA1-XCsxPbBr3 Perovskite for Light Emitting Diode Application", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019.
  • Zhifang Wu, “Highly Efficient and Stable Perovskite Solar Cells via Perovskite Surface Modification", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019.
  • Zhifang Wu, “Improved Efficiency and Stability of Perovskite Solar Cells Induced by C=O Functionalized Hydrophobic Ammonium-Based Additives", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019.
  • Collin Stecker, “Surface Defects of CH3NH3PbBr3 and Their Effect on Interfacial Device Properties", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019.
  • Collin Stecker, “Lead-Halide Perovskite Surface Defects and Their Implications for Device Interface Engineering", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019.
  • Collin Stecker, “Dynamics and Interfacial Effects of Intrinsic Surface Defects at the Atomic-Scale in CH3NH3PbBr3", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019.
  • Afshan Jamshaid, “Atomic Scale Analysis and Electronic Properties Characterization of MAPbI3 Perovskite Material", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019.
  • Afshan Jamshaid, “Atomic Scale Analysis of Perovskite CH3NH3PbI3 Ultra-Thin Films by Scanning Tunneling Microscopy", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019.
  • Afshan Jamshaid, “Atomic Scale Analysis of Perovskite MAPbI3 for Light Emitting Applications", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019.
  • Luis K. Ono, “Influences of Selective Contacts on the Performance and Stability of Perovskite Solar Cells", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019.
  • Luis K. Ono, “Thin-Film Processing by Chemical Vapor Deposition for Large-Scale Optoelectronic Applications", 2019 Materials Research Society (MRS) Spring Meeting & Exhibit, Phoenix, AZ USA, April 22–26, 2019.
  • Yabing Qi, “Investigations on Perovskite Materials and Solar Cells by Surface Science and Advanced Characterization", 10th International Conference on Materials for Advanced Technologies (ICMAT 2019), Marina Bay Sands, Singapore, June 23-28, 2019. (Invited talk)
  • Yabing Qi, “Investigations on Perovskite Materials and Solar Cells by Surface Science and Advanced Characterization", The 26th International Workshop on Active-Matrix Flat panel Displays And Devices (AM-FPD19), Ryukoku University Avanti Kyoto Hall, Kyoto, Japan, July 2-5, 2019. (Invited talk)
  • Yabing Qi, “Investigations on Perovskite Materials and Solar Cells by Surface Science and Advanced Characterization", 2019 Materials Research Society (MRS) Fall Meeting & Exhibit, Boston, MA USA, December 1–6, 2019. (Invited talk)
  • Longbin Qiu, “High Performance Scalable Perovskite Solar Modules by Hybrid Chemical Vapor Deposition", 2019 Materials Research Society (MRS) Fall Meeting & Exhibit, Boston, MA USA, December 1–6, 2019.
  • Sisi He, “Carbon-Based Electrode Engineering Boosts the Efficiency of All Low-Temperature Processed Perovskite Solar Cells", 2019 Materials Research Society (MRS) Fall Meeting & Exhibit, Boston, MA USA, December 1–6, 2019.
  • Luis K. Ono, “Up-Scalable Fabrication of Metal Halide Perovskite Solar Cells and Modules", 2019 Materials Research Society (MRS) Fall Meeting & Exhibit, Boston, MA USA, December 1–6, 2019.
  • Luis K. Ono, “Up-Scalable Fabrication of Metal Halide Perovskite Solar Cells and Modules", Materials Research Meeting 2019 (MRM 2019), Yokohama Symposia, Japan, December 10-14, 2019.

5. Intellectual Property Rights and Other Specific Achievements

N/A

6. Meetings and Events

  • Date: December 13 -15th, 2019
  • Venue: Chengdu, China
  • Title: International Symposium on Perovskites for Optoelectronic Application and Beyond