Methylammonium lead iodide grain boundaries exhibit depth-dependent electrical properties

MacDonald, Gordon A.; Yang, Mengjin; Berweger, Samuel; Killgore, Jason P.; Kaboš, Pavel; Berry, Joseph J.; Zhu, Kai; DelRio, Frank W.

doi:10.1039/c6ee01889k

Cited by 47 publications

(71 citation statements)

References 29 publications

(60 reference statements)

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“…MacDonald et al [182] revealed that GBs demonstrated a depthdependent resistivity, and that this inhomogeneity was one of the limits for the improvement of PSC efficiency. In view of the importance of GBs, further studies are expected to be dedicated towards their detailed investigation.…”

Section: Wwwadvancedsciencenewscommentioning

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

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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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Section: Wwwadvancedsciencenewscommentioning

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

304

201

View full text Add to dashboard Cite

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“…Xing et al [86] also observed that devices with larger crystal size exhibit higher activation energy, that is, ions have to overcome higher barrier to migrate. MacDonald et al [87] reveal that GBs demonstrates the depthdependent resistivity, and this inhomogeneity is one of the limits for the improvement of PSC efficiency. Therefore, with the concern of the importance of GB, further works will be dedicated on their detailed investigation.…”

Section: Detailed Migration Process -Migration Channelsmentioning

confidence: 99%

Origins and mechanisms of hysteresis in organometal halide perovskites

Guerrero

Zhong

et al. 2017

J. Phys.: Condens. Matter

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Inorganic–organic halide organometal perovskites, such as CH3NH3PbI3 and CsPbI3, etc, have been an unprecedented rising star in the field of photovoltaics since 2009, owing to their exceptionally high power conversion efficiency and simple fabrication processability. Despite its relatively short history of development, intensive investigations have been concentrating on this material; these have ranged from crystal structure analysis and photophysical characterization to performance optimization and device integration, etc. Yet, when applied in photovoltaic devices, this material suffers from hysteresis, that is, the difference of the current–voltage (I–V) curve during sweeping in two directions (from short-circuit towards open-circuit and vice versa). This behavior may significantly impede its large-scale commercial application. This Review will focus on the recent theoretical and experimental efforts to reveal the origin and mechanism of hysteresis. The proposed origins include (1) ferroelectric polarization, (2) charge trapping/detrapping, and (3) ion migration. Among them, recent evidence consistently supports the idea that ion migration plays a key role for the hysteretic behavior in perovskite solar cells (PSCs). Hence, this Review will summarize the recent results on ion migration such as the migrating ion species, activation energy measurement, capacitive characterization, and internal electrical field modulation, etc. In addition, this Review will also present the devices with alleviation/elimination of hysteresis by incorporating either large-size grains or phenyl-C61-butyric acid methyl ester molecules. In a different application, the hysteretic property has been utilized in photovoltaic and memristive switching devices. In sum, by examining these three possible mechanisms, it is concluded that the origin of hysteresis in PSCs is associated with a combination of effects, but mainly limited by ion/defect migration. This strong interaction between ion motion and free charge carrier transport can be modulated by the prevalent crystalline structure, chemical passivation, and an external photo/electrical field.

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“…12 Briefly, a nonstoichiometric solution of MAI and PbI 2 (MAI/PbI 2 ratio of 1.2:1) is deposited onto a compact TiO 2 layer on fluorine-doped tin oxide (FTO). These films are then subjected to solvent bathing in an antisolvent, followed by an annealing step at ~150 °C.…”

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confidence: 99%

Electronic and Morphological Inhomogeneities in Pristine and Deteriorated Perovskite Photovoltaic Films

et al. 2017

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We perform scanning microwave microscopy (SMM) to study the spatially varying electronic properties and related morphology of pristine and degraded methylammonium lead-halide (MAPI) perovskite films fabricated under different ambient humidity. We find that higher processing humidity leads to the emergence of increased conductivity at the grain boundaries but also correlates with the appearance of resistive grains that contain PbI2. Deteriorated films show larger and increasingly insulating grain boundaries as well as spatially localized regions of reduced conductivity within grains. These results suggest that while humidity during film fabrication primarily benefits device properties due to the passivation of traps at the grain boundaries and self-doping, it also results in the emergence of PbI2-containing grains. We further establish that MAPI film deterioration under ambient conditions proceeds via the spatially localized breakdown of film conductivity, both at grain boundaries and within grains, due to local variations in susceptibility to deterioration. These results confirm that PbI2 has both beneficial and adverse effects on device performance and provide new means for device optimization by revealing spatial variations in sample conductivity as well as morphological differences in resistance to sample deterioration.

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Methylammonium lead iodide grain boundaries exhibit depth-dependent electrical properties

Abstract: In this communication, the nanoscale through-film and lateral photo-response and conductivity of large-grained methylammonium lead iodide (MAPbI3) thin films are studied.

Cited by 47 publications

References 29 publications

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

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

Origins and mechanisms of hysteresis in organometal halide perovskites

Electronic and Morphological Inhomogeneities in Pristine and Deteriorated Perovskite Photovoltaic Films

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