Grain boundary dominated ion migration in polycrystalline organic–inorganic halide perovskite films

Shao, Yuchuan; Fang, Yanjun; Li, Tao; Wang, Qi; Dong, Qingfeng; Deng, Yehao; Yuan, Yongbo; Wei, Haotong; Wang, Meiyu; Gruverman, Alexei; Shield, Jeffery E; Huang, Jinsong

doi:10.1039/c6ee00413j

Cited by 999 publications

(999 citation statements)

References 44 publications

(62 reference statements)

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“…The ion diffusion is expected to be suppressed as well by filling the relatively open grain boundaries with nonmobile fullerene balls, which also interact with defects at grain boundaries. [61] This aligns well with another study, which also observed the improvement in overall performance and suppression of I-V hysteresis due to PCBM passivation of iodide-rich trap sites on the surface of perovskite films. [62] Direct observation of the faster ion migration at grain boundaries was shown by measuring a different elemental redistribution along the grain boundaries compared to the grain interior after electrical poling.…”

Section: Grain Boundaries Passivation and Ion Migrationsupporting

confidence: 77%

“…This change in conductive properties was considered to be an indication of ion migration under illumination, one of the likely origins of hysteresis in perovskite solar cells. [61] Both the dark-current and photocurrent hysteresis at the grain boundaries could be suppressed in the presence of PCBM, as seen in Figure 4f, steady-state PL spectra showing the relative PL intensities before (blue circle) and after (red square) pyridine treatment. Reproduced with permission.…”

Section: Grain Boundaries Passivation and Ion Migrationmentioning

confidence: 78%

“…[61] They found a significant hysteresis in the dark current at the grain boundaries, whereas the grain interior showed negligible hysteresis (Figure 4c-e), suggesting that ions are more likely to migrate near the grain boundaries. [61] Placing the c-AFM tip on a grain boundary and measuring the short circuit current under illumination revealed a clear increase in the photocurrent at the grain boundary over time, whereas the grain interior remained relatively constant. This change in conductive properties was considered to be an indication of ion migration under illumination, one of the likely origins of hysteresis in perovskite solar cells.…”

Section: Grain Boundaries Passivation and Ion Migrationmentioning

confidence: 99%

“…"Bumps" and "pinholes" were observed particularly at and near the grain boundaries, indicating that ions moving in the applied electric field are much more free to do so at the boundaries compared to the interior of the grains. [61] The iodine signal changes dramatically after poling, with a gradient across the grain boundary, increasing from the cathode to the anode side. The iodine concentration at the grain interior, however, remains the same.…”

Section: Grain Boundaries Passivation and Ion Migrationmentioning

confidence: 99%

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Microstructural Characterisations of Perovskite Solar Cells – From Grains to Interfaces: Techniques, Features, and Challenges

Rothmann

Etheridge

et al. 2017

Advanced Energy Materials

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group of crystals that all share the same type of crystal structure based on CaTiO 3 , namely ABX 3 , with A cations, such as methylammonium (CH 3 NH 2 + ), formamidinium (CH(NH 2 ) 2 + ), and cesium (Cs + ); B cations such as tin (Sn 2+ ) and lead (Pb 2+ ); and halides, such as iodide (I − ), bromide (Br − ), and chloride (Cl − ), as the X anion. Since the first report of a solar cell using a hybrid organic-inorganic perovskite by Miyasaka et al. in 2009, the solar cells' efficiency has rapidly increased from 3.8% [2] to over 22.1% [3] certified for laboratoryscale devices. This rapid increase is due in part to intense efforts to develop novel device architectures that are energetically favorable for charge generation and extraction, coupled with basic studies detailing the intrinsic properties of the photoactive perovskite materials. [4] However, this record efficiency is still well below the theoretical limit of ≈31% for a singlejunction photovoltaic device. [5] Significant improvements in processing technologies are needed, which in turn require a detailed understanding of microstructures, interface structures, and overall architectures of the solar cell device."Microstructure", the fine structure of a material from the micrometer to the atomic scale, plays an important role in determining the performance of many types of solar cells in use and under development today. In single crystal photoactive materials like silicon, the intragrain defects, such as stacking faults and dislocations, attract significant research interest since these intragrain defects tend to be decorated by impurities, causing higher recombinative losses in these areas. [6] In polycrystalline materials, such as CdTe, grain boundaries have been found to be a limiting factor in solar cell performance due to an enhanced recombination at the grain boundaries. [7] Modification of the grain boundaries by chlorine can assist electron-hole pair separation and positively contribute to carrier collection efficiency. [7,8] Clearly, detailed knowledge of the microstructures in conventional solar cell materials has played a significant role in understanding and improving the underlying processes that govern overall solar cell performance. Further improvements in power conversion efficiency beyond the current record of 22.1%, as well as improved performance stability of perovskite solar cells, are therefore anticipated through in-depth characterization and understanding of their microstructures.Organic-inorganic hybrid perovskite solar cells form a new type of thin film photovoltaic technology, which has achieved extraordinary improvements in power conversion efficiency in a relatively short time. To further improve the efficiency and stability of the perovskite solar cells, it is critical to understand and control the microstructure of both the functional materials and their interfaces. Much effort has already been made to understand the microstructure of perovskite solar cells and its influence on their performance. This has proved particularly cha...

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Section: Grain Boundaries Passivation and Ion Migrationsupporting

confidence: 77%

Section: Grain Boundaries Passivation and Ion Migrationmentioning

confidence: 78%

Section: Grain Boundaries Passivation and Ion Migrationmentioning

confidence: 99%

Section: Grain Boundaries Passivation and Ion Migrationmentioning

confidence: 99%

See 2 more Smart Citations

Microstructural Characterisations of Perovskite Solar Cells – From Grains to Interfaces: Techniques, Features, and Challenges

Rothmann

Etheridge

et al. 2017

Advanced Energy Materials

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“…For example, Xiao et al [173] found that, compared with large crystal size devices, films composed of smaller size grains can be more easily switched under external electric fields. By carrying out conducting atomic force microscopy (c-AFM), and scanning electron microscopy (SEM), Shao et al [179] concluded that GBs where these defects resided were the fast moving channel for ion migration. Moreover, Yun et al [180] conducted Kelvin probe force microscopy (c-KFM) to reveal that ion migration near GBs was much faster than inside the grains.…”

Section: Ion Migration Processmentioning

confidence: 99%

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

Petrus

Schlipf

Cheng

et al. 2017

Advanced Energy Materials

312

201

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following statement: These materials can be processed from solution and yet exhibit optoelectronic materials properties described in classic solid-state physics textbooks. This unprecedented combination has led to photovoltaic devices that can be processed at room temperature and achieve performance levels similar to industry giant polycrystalline silicon, from a starting point of 3.8% in 2009. [1][2][3][4] The first light-emitting electrochemical cells [5] and diodes [6][7][8] have also been introduced recently, leading to tunable light emission spectra and internal quantum efficiencies exceeding 15%.The road towards these achievements has been marked by a constant improvement of perovskite deposition techniques fueled by our increasing understanding of the crystallization processes. The choice of deposition technique, either from solution or vapor, and the composition and order in which precursor species are applied has a great influence on the crystallization kinetics. Here, one can distinguish one-step methods where the perovskite is formed from a precursor mixture dissolved in a common solution, and two-step methods where the inorganic compound is deposited first and transformed to the perovskite phase later by addition of the organic constituents. [9][10][11] Furthermore, many parameters during processing can have an effect on the crystallization mechanism and consequently on film morphology, such as the choice of solvents, concentrations and processing additives that are often not incorporated into the final product. [11][12][13] We discuss this aspect in Section 2, where we focus our attention on the most commonly employed solution-based techniques. Additionally, as for any new technology trying to displace an incumbent technology, higher efficiencies, lower costs, reproducibility, stability, and sustainability are paramount. In particular, reproducibility has been a major challenge in perovskite solar cells from the beginning: small variations in morphology, like crystal size, film roughness, and pinholes can have detrimental effects on photovoltaic performance. [14] On the other hand, current-voltage measurements often showed a hysteresis that is rarely seen in other photovoltaic technologies. [15] These topics are highlighted in Sections 3 and 4. Finally, in Section 5 we discuss the framework for market introduction, such as cost reduction by choosing low-cost charge transport layers, or how the lifetime of perovskite absorbers can be extended by the choice of materials composition.Hybrid metal halide perovskites have become one of the hottest topics in optoelectronic materials research in recent years. Not only have they surpassed everyone's expectations and achieved similar performance as tried and true polycrystalline silicon photovoltaic devices, but they are also finding applications in a variety of different fields, including lighting. The main advantages of hybrid metal halide perovskites are simple processability, compatible with large-scale solution processing such as roll-to-roll printing, a...

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2023

Defects in Organic Semiconductors and Devices

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Grain boundary dominated ion migration in polycrystalline organic–inorganic halide perovskite films

Abstract: Grain boundaries have been demonstrated as the dominating ion migration channels in polycrystalline organic–inorganic halide perovskite films.

Cited by 999 publications

References 44 publications

Microstructural Characterisations of Perovskite Solar Cells – From Grains to Interfaces: Techniques, Features, and Challenges

Microstructural Characterisations of Perovskite Solar Cells – From Grains to Interfaces: Techniques, Features, and Challenges

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

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