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Title: Impact of grain boundaries on efficiency and stability of organic-inorganic trihalide perovskites

Abstract

Organic-inorganic perovskite solar cells have attracted tremendous attention because of their remarkably high power conversion efficiencies. To further improve device performance, it is imperative to obtain fundamental understandings on the photo-response and long-term stability down to the microscopic level. Here, we report the quantitative nanoscale photoconductivity imaging on two methylammonium lead triiodide thin films with different efficiencies by light-stimulated microwave impedance microscopy. The microwave signals are largely uniform across grains and grain boundaries, suggesting that microstructures do not lead to strong spatial variations of the intrinsic photo-response. In contrast, the measured photoconductivity and lifetime are strongly affected by bulk properties such as the sample crystallinity. As visualized by the spatial evolution of local photoconductivity, the degradation process begins with the disintegration of grains rather than nucleation and propagation from visible boundaries between grains. In conclusion, our findings provide insights to improve the electro-optical properties of perovskite thin films towards large-scale commercialization.

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [2];  [1];  [1];  [1];  [1];  [1]; ORCiD logo [2];  [1]
  1. Univ. of Texas at Austin, Austin, TX (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
OSTI Identifier:
1416518
Report Number(s):
NREL/JA-5900-68285
Journal ID: ISSN 2041-1723
Grant/Contract Number:
AC36-08GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 8; Journal Issue: 1; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 42 ENGINEERING; electronic properties; electronic materials; organic-inorganic nanostructures; solar cells

Citation Formats

Chu, Zhaodong, Yang, Mengjin, Schulz, Philip, Wu, Di, Ma, Xin, Seifert, Edward, Sun, Liuyang, Li, Xiaoqin, Zhu, Kai, and Lai, Keji. Impact of grain boundaries on efficiency and stability of organic-inorganic trihalide perovskites. United States: N. p., 2017. Web. doi:10.1038/s41467-017-02331-4.
Chu, Zhaodong, Yang, Mengjin, Schulz, Philip, Wu, Di, Ma, Xin, Seifert, Edward, Sun, Liuyang, Li, Xiaoqin, Zhu, Kai, & Lai, Keji. Impact of grain boundaries on efficiency and stability of organic-inorganic trihalide perovskites. United States. doi:10.1038/s41467-017-02331-4.
Chu, Zhaodong, Yang, Mengjin, Schulz, Philip, Wu, Di, Ma, Xin, Seifert, Edward, Sun, Liuyang, Li, Xiaoqin, Zhu, Kai, and Lai, Keji. 2017. "Impact of grain boundaries on efficiency and stability of organic-inorganic trihalide perovskites". United States. doi:10.1038/s41467-017-02331-4. https://www.osti.gov/servlets/purl/1416518.
@article{osti_1416518,
title = {Impact of grain boundaries on efficiency and stability of organic-inorganic trihalide perovskites},
author = {Chu, Zhaodong and Yang, Mengjin and Schulz, Philip and Wu, Di and Ma, Xin and Seifert, Edward and Sun, Liuyang and Li, Xiaoqin and Zhu, Kai and Lai, Keji},
abstractNote = {Organic-inorganic perovskite solar cells have attracted tremendous attention because of their remarkably high power conversion efficiencies. To further improve device performance, it is imperative to obtain fundamental understandings on the photo-response and long-term stability down to the microscopic level. Here, we report the quantitative nanoscale photoconductivity imaging on two methylammonium lead triiodide thin films with different efficiencies by light-stimulated microwave impedance microscopy. The microwave signals are largely uniform across grains and grain boundaries, suggesting that microstructures do not lead to strong spatial variations of the intrinsic photo-response. In contrast, the measured photoconductivity and lifetime are strongly affected by bulk properties such as the sample crystallinity. As visualized by the spatial evolution of local photoconductivity, the degradation process begins with the disintegration of grains rather than nucleation and propagation from visible boundaries between grains. In conclusion, our findings provide insights to improve the electro-optical properties of perovskite thin films towards large-scale commercialization.},
doi = {10.1038/s41467-017-02331-4},
journal = {Nature Communications},
number = 1,
volume = 8,
place = {United States},
year = 2017,
month =
}

Journal Article:
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  • Ionicity plays an important role in determining material properties, as well as optoelectronic performance of organometallic trihalide perovskites (OTPs). Ion migration in OTP films has recently been under intensive investigation by various scanning probe microscopy (SPM) techniques. Controversial findings regarding the role of grain boundaries (GBs) associated with ion migration are often encountered, likely as a result of feedback errors and topographic effects common in to SPM. In this work, electron microscopy and spectroscopy (scanning transmission electron microscopy/electron energy loss spectroscopy) are combined with a novel, open-loop, band-excitation, (contact) Kelvin probe force microscopy (BE-KPFM and BE-cKPFM), in conjunction with abmore » initio molecular dynamics simulations to examine the ion behavior in the GBs of CH 3NH 3PbI 3 perovskite films. Furthermore, this combination of diverse techniques provides a deeper understanding of the differences between ion migration within GBs and interior grains in OTP films. Our work demonstrates that ion migration can be significantly enhanced by introducing additional mobile Cl - ions into GBs. The enhancement of ion migration may serve as the first step toward the development of high-performance electrically and optically tunable memristors and synaptic devices.« less
    Cited by 1
  • Cited by 1
  • The organic-inorganic hybrid lead trihalide perovskites have been emerging as the most attractive photovoltaic materials. As regulated by Shockley-Queisser theory, a formidable materials science challenge for improvement to the next level requires further band-gap narrowing for broader absorption in solar spectrum, while retaining or even synergistically prolonging the carrier lifetime, a critical factor responsible for attaining the near-band-gap photovoltage. Herein, by applying controllable hydrostatic pressure, we have achieved unprecedented simultaneous enhancement in both band-gap narrowing and carrier-lifetime prolongation (up to 70% to -100% increase) under mild pressures at -0.3 GPa. The pressure-induced modulation on pure hybrid perovskites without introducing anymore » adverse chemical or thermal effect clearly demonstrates the importance of band edges on the photon-electron interaction and maps a pioneering route toward a further increase in their photovoltaic performance.« less