Suppressed Ion Migration along the In-Plane Direction in Layered Perovskites

Xiao, Xun; Dai, Jun; Fang, Yanjun; Zhao, Jingjing; Zheng, Xiaopeng; Tang, Shi; Rudd, Peter N.; Zeng, Xiao Cheng; Huang, Jinsong

doi:10.1021/acsenergylett.8b00047

Cited by 283 publications

(313 citation statements)

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“…[10] The magnitude of postsynaptic current was smallest in the 2D perovskite synapse; its calculated energy consumption was also lowest when voltage amplitude and pulse width were fixed (Figure 6a). Compared with the recently reported energy consumption of fabricated artificial synapses (Figure 6b and Table S2, Supporting Information), [5,12,13,22,[29][30][31][32][33][34][35][36][37][38][39][40] our OHP artificial synapses show much higher energy efficiency despite having larger dimension. Also, we further economized on energy consumption of the device by decreasing the magnitude of voltage pulse (≈0.7 fJ per synaptic event at voltage pulse = −0.02 V and read voltage = −0.01 V) ( Figure S10, Supporting Information).…”

Section: Wwwadvelectronicmatdementioning

confidence: 58%

“…Moreover, various structural modulation of polycrystalline films is possible with facile solution processing so that organic parts in the OHPs can control the ion migration and electrical conduction. [11][12][13] Thereby, the activation energy E A of ion migration is increased, so ion migration and excitatory postsynaptic current (EPSC) can be reduced. [7] OHPs have a significant hysteresis property that is caused by ion migration or space charges, or both, which may enable gradual modulation of conductance in OHP.…”

mentioning

confidence: 99%

“…[11][12][13] Thereby, the activation energy E A of ion migration is increased, so ion migration and excitatory postsynaptic current (EPSC) can be reduced. For this purpose, we replaced the small MA ion with a bulky phenethylammonium (PEA) ion in their crystalline structures.…”

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confidence: 99%

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Dimensionality Dependent Plasticity in Halide Perovskite Artificial Synapses for Neuromorphic Computing

Kim

Lee

Park

et al. 2019

Adv Elect Materials

134

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properties of biological synapses and perform parallel operations, they require larger energy than a biological synapse. Therefore, development of an artificial synapse with energy consumption on the level of a biological synapse remains an open problem.Organic-inorganic halide perovskite (OHPs) may provide a material to solve this problem, because of their low activation energy of ion migration. Moreover, various structural modulation of polycrystalline films is possible with facile solution processing so that organic parts in the OHPs can control the ion migration and electrical conduction. OHPs have an ABX 3 crystal structure; the A-site cation is located at the center of a BX 6 octahedral cage, and the B-site metal cation is surrounded by the six nearest-neighbor X-site halide anions. [7] OHPs have a significant hysteresis property that is caused by ion migration or space charges, or both, which may enable gradual modulation of conductance in OHP. [8] Two-terminal artificial synapses based on 3D methylammonium (MA) lead halide perovskite (MAPbX 3 , X = Br, I) films showed synaptic responses that are caused by ion migration in the OHP layer. [9,10] Ion migration in 3D OHP film is induced by relatively low activation energy and a low energy consumption of ≈20 fJ per synaptic event was achieved in the synaptic devices. However, the energy consumption could be further reduced to the energy level of biological synapses when the ion migration was controlled by engineering the structure of OHP films could be optimally done.In this work, we introduce 2D and quasi-2D OHP films into artificial synapses to enable control of ion migration and resultant synaptic responses. For this purpose, we replaced the small MA ion with a bulky phenethylammonium (PEA) ion in their crystalline structures. To prepare 2D, quasi-2D, and 3D OHP films, we controlled the stoichiometric ratio of PEA and MA cations to induce self-assembly of a layered structure. This replacement of an MA cation with PEA cation suppresses ion migration in the out-of-plane direction of the OHP films. [11][12][13] Thereby, the activation energy E A of ion migration is increased, so ion migration and excitatory postsynaptic current (EPSC) can be reduced. Also, energy consumption of the device is reduced to ≈0.7 fJ per synaptic event, which is comparable to that of biological synapses. Memory retention of artificial The hysteretic behavior of organic-inorganic halide perovskites (OHPs) are exploited for application in neuromorphic electronics. Artificial synapses with 2D and quasi-2D perovskite are demonstrated that have a bulky organic cation (phenethylammonium (PEA)) to form structures of (PEA) 2 MA n-1 Pb n Br 3n+1 . The OHP films have morphological properties that depend on their structure dimensionality (i.e., n value), and artificial synapses fabricated from them show synaptic responses such as short-term plasticity, paired-pulse facilitation, and long-term plasticity. The operation mechanism of OHP artificial synapses are also analyzed depending on the dimen...

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Section: Wwwadvelectronicmatdementioning

confidence: 58%

mentioning

confidence: 99%

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Dimensionality Dependent Plasticity in Halide Perovskite Artificial Synapses for Neuromorphic Computing

Kim

Lee

Park

et al. 2019

Adv Elect Materials

134

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“…This is because of the formation of too thick 2D perovskite capping layers with poor charge transport properties. [65,66] The corresponding incident photon conversion efficiency (IPCE) was carried out to testify the photon energy response of the devices. [ 2D capped 3D perovskite film achieves higher V OC of 1.126 V, a J SC of 22.80 mA cm −2 , and an FF of 0.80, leading to an improved PCE of 20.54%.…”

Section: Photovoltaic Characterization Of the Fpeai Modified Perovskimentioning

confidence: 99%

High‐Performance Perovskite Solar Cells with Enhanced Environmental Stability Based on a (p‐FC₆H₄C₂H₄NH₃)₂[PbI₄] Capping Layer

Zhou

Liang

et al. 2019

Advanced Energy Materials

240

130

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lengths, low exciton binding energy, and ease of solution processability, which promise the perovskite-based photovoltaic devices both high efficiency and low manufacture cost. The intense effort to improve power conversion efficiencies (PCEs) has resulted in PCEs of perovskite solar cells (PSCs) increasing from 3.8% in 2009 [5] to over 23% in 9 years. [6,7] Changes in material composition (e.g., using mixed cations and halides together into a 3D lead−halide perovskites, such as [FA/MA]Pb[I/Br] 3 , [8] [FA/Cs]Pb[I/Br] 3 , [9,10] or [Cs/FA/MA]Pb[I/Br] 3[11] ) have played essential role to improve the performances and structural stability. However, the intrinsic instability of the 3D lead−halide perovskites with regard to moisture, heat, light, and oxygen remains to be entirely circumvented. [12,13] Two main measures have been taken to increase the stability of PSCs: providing sufficient protection to the perovskite material [14] and increasing the intrinsic stability of the perovskite material. [15] More importantly, techniques that can improve device stability without sacrificing the efficiency are critical for the future of PSCs. In this regard, strategies called multidimensional perovskite (MDP) using Ruddlesden-Popper type perovskite (Class I) or low dimensional polymorphs passivated 3D perovskites (Class II) were brought into being increasing the intrinsic stability of the perovskite material. [16] Ruddlesden-Popper phase layered perovskites ((RNH 3 ) 2 (MA) n−1 Pb n X 3n+1 , n = 1, 2, 3, 4, 5, …) [17][18][19][20][21] which was introduced by Smith et al. showed albeit low PCE the superior ambient stability, [18] where RNH 3 are large aliphatic or aromatic ammonium cations represented by n-butylammonium (BA) and 2-phenylethylammonium (PEA). (BA) 2 (MA) 2 Pb 3 I 10 as a light absorber retained its performance after exposure to a highhumidity environment for 60 d. [20] So far the highest reported PCE of Ruddlesden-Popper type perovskite-based solar cell is 15.42%. [22] Very recently, Zhang et al. utilized synchrotron source based in situ measurement to disclose the phase transition kinetics during the crystallization of Ruddlesden-Popper type perovskite. This study provided insight into the relationship between phase purity, quantum well orientation, and photovoltaic performance. [23] On the other hand, the approaches that involve low dimensional polymorphs passivated 3D perovskites, or 3D-2D perovskite stacked structures attracted extensive interest in recent years. This approach features not only the Supported by the density functional theory (DFT) calculations, for the first time, a fluorinated aromatic cation, 2-(4-fluorophenyl)ethyl ammonium iodide (FPEAI), is introduced to grow in situ a low dimensional perovskite layer atop 3D perovskite film with excess PbI 2 . The resulted (p-FC 6 H 4 C 2 H 4 NH 3 ) 2 [PbI 4 ] perovskite functions as a protective capping layer to protect the 3D perovskite from moisture. In the meantime, the thin layer facilitates charge transfer at the interfaces, thereby reducing the...

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large organic ligands with the formula of A 2 A′ n−1 M n X 3n+1 . [13][14][15] Through down-conversion excitation, 2D perovskites have shown efficient light emission in spontaneous [16,17] and stimulated [18,19] regimes. [13][14][15] Through down-conversion excitation, 2D perovskites have shown efficient light emission in spontaneous [16,17] and stimulated [18,19] regimes.

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confidence: 99%

Two‐Photon Up‐Conversion Photoluminescence Realized through Spatially Extended Gap States in Quasi‐2D Perovskite Films

Zhu

Liu

et al. 2019

Advanced Materials

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large organic ligands with the formula of A 2 A′ n−1 M n X 3n+1 . [9][10][11][12] Such 2D perovskites can demonstrate remarkable tunabilities on optical properties via controlling morphological structures by selecting different functional A/A′ molecules. [13][14][15] Through down-conversion excitation, 2D perovskites have shown efficient light emission in spontaneous [16,17] and stimulated [18,19] regimes. Recently, amplified spontaneous emission (ASE) have been reported in 2D perovskites [(NMA) 2 (FA)Pb 2 Br 7 and (NMA) 2 (FA)Pb 2 Br 1 I 6 ] with stoichiometrically tunable wavelength from visible to near-infrared spectral range (530-810 nm) with the gain coefficient as high as > 300 cm −1 under pulse laser excitation. [20] On the other hand, it has been found that the edge states can be formed in 2D perovskites with light-emitting properties below the bandgap. [21] The discovery of edge states triggers a fundamental question of whether the gap states can be introduced as a new approach to develop multi-photon up-conversion light emission in solution-processing quasi-2D perovskite films. We should note that an up-conversion ASE was indeed observed at 720 nm in inorganic 3D perovskite (CsPbI 3 ) nanoplates under the infrared pulse laser excitation of 1200 nm. [22] In this work, we explore a new approach to realize multi-photon up-conversion photoluminescence (PL) in quasi-2D perovskite [(PEA) 2 (MA) 4 Pb 5 Br 16 (n = 5)] films by directly exciting broad gap states with continuous-wave (CW) infrared photoexcitation. The broad gap states were adjusted by selecting different n values (n = 1-5) with accelerated crystallization in quasi-2D perovskite films prepared with antisolvent processing method. Here, we found that an up-conversion PL can be observed in 2D perovskite [(PEA) 2 (MA) 4 Pb 5 Br 16 (n = 5)] films under CW 980 nm excitation when broad infrared absorption is appeared between 800 and 1500 nm. To further understand the up-conversion PL under CW infrared excitation, magnetic field effects of PL (namely, magneto-PL) were used to identify whether the gap states function as spatially extended states to generate multiphoton absorption in quasi-2D perovskite films. Furthermore, polarization-dependent PL upon using linearly and circularly polarized photoexcitations was used to explore the effects of orbit-orbit interaction on multi-photon up-conversion PL under A new approach to generate a two-photon up-conversion photoluminescence (PL) by directly exciting the gap states with continuous-wave (CW) infrared photoexcitation in solution-processing quasi-2D perovskite films [(PEA) 2 (MA) 4 Pb 5 Br 16 with n = 5] is reported. Specifically, a visible PL peaked at 520 nm is observed with the quadratic power dependence by exciting the gap states with CW 980 nm laser excitation, indicating a two-photon up-conversion PL occurring in quasi-2D perovskite films. Decreasing the gap states by reducing the n value leads to a dramatic decrease in the twophoton up-conversion PL signal. This confirms that the gap states are indeed ...

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Suppressed Ion Migration along the In-Plane Direction in Layered Perovskites

Cited by 283 publications

References 38 publications

Dimensionality Dependent Plasticity in Halide Perovskite Artificial Synapses for Neuromorphic Computing

Dimensionality Dependent Plasticity in Halide Perovskite Artificial Synapses for Neuromorphic Computing

High‐Performance Perovskite Solar Cells with Enhanced Environmental Stability Based on a (p‐FC₆H₄C₂H₄NH₃)₂[PbI₄] Capping Layer

Two‐Photon Up‐Conversion Photoluminescence Realized through Spatially Extended Gap States in Quasi‐2D Perovskite Films

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Suppressed Ion Migration along the In-Plane Direction in Layered Perovskites

Cited by 283 publications

References 38 publications

Dimensionality Dependent Plasticity in Halide Perovskite Artificial Synapses for Neuromorphic Computing

Dimensionality Dependent Plasticity in Halide Perovskite Artificial Synapses for Neuromorphic Computing

High‐Performance Perovskite Solar Cells with Enhanced Environmental Stability Based on a (p‐FC6H4C2H4NH3)2[PbI4] Capping Layer

Two‐Photon Up‐Conversion Photoluminescence Realized through Spatially Extended Gap States in Quasi‐2D Perovskite Films

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High‐Performance Perovskite Solar Cells with Enhanced Environmental Stability Based on a (p‐FC₆H₄C₂H₄NH₃)₂[PbI₄] Capping Layer