Perovskite-Like Organic–Inorganic Hybrid Lead Iodide with a Large

Article pubs.acs.org/IC

Perovskite-Like Organic−Inorganic Hybrid Lead Iodide with a Large Organic Cation Incorporated within the Layers Chen-Jie Que, Chong-Jiao Mo, Zhao-Qi Li, Guang-Lin Zhang, Qin-Yu Zhu,* and Jie Dai* College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, P. R. China S Supporting Information *

ABSTRACT: A great effort has been made to investigate 2D perovskites to improve the stability and controllability in the fabrication of photoelectronic devices. As far as we know, only small organic cations such as methylammonium can incorporate into the multilayered perovskite structure except the cations sandwiched between the inorganic layers. We report here a new layered lead iodide, (H2Aepz)3Pb4I14 (1), where larger organic cations, bis-protonated 2-(2-aminoethyl)pyrazole (Aepz), not only were sandwiched between the inorganic layers but also were incorporated within the perovskite-like PbI layered structure. Another 2D compound, (H2Aepz)PbI4 (2), was also prepared that was a one-layer perovskite. A simple Schottky device was prepared to investigate the photoelectroresponsive properties of the compounds in comparison with that of a typical organic−inorganic hybrid perovskite. In general, the energy gap is decreased with an increase in the perovskite layers, but the band gap of two-layered 1 is larger than that of one-layered 2. The photocurrent densities of the compounds are in the order of 1 < 2 < (CH3NH3)PbI3, which is discussed based on the crystal structures and band energy gaps.

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moisture. High-quality films were obtained through a simple spin-coating method.11 The thick 3D-like layered structure formed by three MAPbI3 sheets, separated by bulkier PEA ammonium cations. The CH3NH3+ cations are incorporated within the perovskite sheets. As far as we know, only small CH3NH3+ or CH(NH2)2+ cations6 can incorporate into the multilayered perovskite structure. We obtained recently layered perovskite-like lead iodides, (H2Aepz)3Pb4I14 (1) and (H2Aepz)PbI4 (2). In 1, an organic cation [bis-protonated 2-(2-aminoethyl)pyrazole, H2Aepz2+] not only was sandwiched between the inorganic perovskite-like layers but also was incorporated within the PbI layered anion structure. By a partial change of the corner-shared link mode of PbI octahedra in MAPbI3 to the edge-shared mode, larger cavities where H2Aepz2+ cations loaded are formed. It is an unusual structure of perovskite-like materials. The finding may encourage us to look for new hybrid perovskite-like materials with small functional organic cations. Another 2D compound (2) is a one-layer perovskite with the same cation as 1. A simple Schottky device was prepared to investigate the photoelectroresponsive properties of the compounds in comparison with that of a typical organic−inorganic hybrid perovskite MAPbI3. The photoelectric response properties of the compounds are discussed based on the crystal structures and band energy gaps.

INTRODUCTION Organic−inorganic hybrid halides have been used to fabricate high-efficiency all-solid-state solar cells in the past few years.1−3 The materials methylammonium lead halide, MAMX3 (MA = CH3NH3; X = Cl, Br, I), allowed us to reach an astonishing efficiency for solar energy transfer.4,5 A great effort has been made to investigate other perovskite-like materials by selecting different organic cations.6−8 Investigation of 2D perovskites has been growing recently with the aim not only to improve their stability but also to improve the diversity and controllability in the fabrication of photoelectronic devices.9−11 Although 2D hybrid perovskites have shown larger band gaps than MAPbX3,12,13 layered materials present great flexibility and can intercalate various cations as well as be easily deposited to form homogeneous thin films. Thus, 2D perovskites with a suitable band gap could be very interesting for applications in mesoscopic solar cells. The interlayer separation and thickness of the inorganic layers can be controlled through the choice of organic cations.14−16 Most of the 2D perovskites are one-sheet compounds with bulkier monovalent (A) or divalent (B) ammonium cations sandwiched between the inorganic layers formulated as A2PbI4 and BPbI4.17−24 Some two-sheet perovskites are reported,25,26 exemplified by (C4H3SCH2NH3)2(MA)Pb2I7. The inorganic part consists of a bilayer of corner-sharing distorted PbI octahedra with incorporated MA (CH3NH3+) cations. The protonated C4H3SCH2NH3+ cations are sandwiched between the layers.25 A thick layered perovskite with mixed composition, (PEA)2(MA)2Pb3I10 [PEA = C6H5(CH2)2NH3+], has been proposed as a light absorber with enhanced stability to © XXXX American Chemical Society

Received: October 20, 2016

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DOI: 10.1021/acs.inorgchem.6b02550 Inorg. Chem. XXXX, XXX, XXX−XXX

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EXPERIMENTAL SECTION

of 3:1 Pb(OAc)2/Aepz for 1 and 1:2 Pb(OAc)2/Aepz for 2 (see the Experimental Section). Their single crystals for structure analysis were grown with a programmed cooling method. The XRD patterns of the bulky microcrystal samples are in agreement with those simulated from the data of single-crystal analysis (Figure S1), which indicate that these compounds are stable in ambient conditions and the purity of the bulky samples was ensured. The FT-IR data of the compounds are listed in the Experimental Section (also see Figure S2). Both 1 and 2 show broad νN−H (from 2800 to 3350 cm−1) vibrations with the characteristic feature of a hydrogen bond that overlaps with the νC−H vibrations. The strong absorption band at 1450 cm−1 and broad bands around 650−750 cm−1 are attributed to the organic cation because the Pb−I and Pb−I−Pb vibrations appear in very lower energy.30 Solid-state UV−vis absorption spectra of the compounds, calculated from the diffusereflectance spectra, are shown in Figure 1a along with the

General Remarks. All analytically pure reagents were purchased commercially and used without further purification. The Fourier transform infrared (FT-IR) spectra were recorded as KBr pellets on a Nicolet Magna 550 FT-IR spectrometer. Solid-state room-temperature optical diffuse-reflectance spectra of the microcrystal samples or films were obtained with a Shimadzu UV-3150 spectrometer. Roomtemperature X-ray diffraction (XRD) data were collected on a D/ MAX-3C diffractometer using a copper tube source (Cu Kα, λ = 1.5406 Å). The morphologies of the films were recorded by scanning electron microscopy (SEM; JSM-5600LV). Cyclic voltammetry (CV) experiments of the solid-state compounds were performed in acetonitrile with 0.10 mol/L tetrabutylamonium perchloride on a CHI660 electrochemistry workstation in a three-electrode system with a sample-deposited platinum-plate working electrode, a platinum wire auxiliary electrode, and a saturated calomel reference electrode. Thermogravimetric analysis (TGA) was carried out with a SDT 2960 thermal analyzer. The samples were heated under a nitrogen stream of 100 mL/min with a heating rate of 10 °C/min. Synthesis of (H2Aepz)3Pb4I14 (1) and (H2Aepz)PbI4 (2). Compound 1. Pb(OAc)2·3H2O (0.0568 g, 0.15 mmol) and Aepz (0.0092 g, 0.05 mmol) were mixed with 0.50 mL of HI (>45% in water) in a thick Pyrex tube (0.7 cm diameter; 15 cm length). The sealed tube was heated to 70 °C and then cooled to 40 °C by a programmed cooling method with 1 °C/h. Yellow crystals were obtained from the cooled solution after 30 h, washed with ethanol, and then dried (55% yield based on lead). Anal. Calcd for C15H33N9Pb4I14 (Mw = 2944.95): C, 6.11; H, 1.12; N, 4.28. Found: C, 6.21; H, 1.24; N, 4.42. Important IR data (KBr, cm−1): 2970 (m), 2928 (w), 2865 (w), 1630 (m), 1512 (w), 1382 (s), 1128 (m), 1010 (m), 858 (w), 749 (w), 663 (m). Compound 2. Compound 2 was obtained by a similar solvothermal method. Pb(OAc)2·3H2O (0.0190 g, 0.05 mmol) and Aepz (0.0184 g, 0.1 mmol) were mixed with 0.50 mL of 45% HI. Red crystals were obtained from the cooled solution, washed with ethanol, and then dried (48% yield based on lead). Anal. Calcd for C5H11N3PbI4 (Mw = 827.98): C, 7.25; H, 1.33; N, 5.07. Found: C, 7.31; H, 1.53; N, 5.00. Important IR data (KBr, cm−1): 2970 (m), 2928 (w), 2865 (w), 1630 (m), 1512 (w), 1382 (s), 1128 (m), 1010 (m), 858 (w), 749 (w), 663 (m). X-ray Crystallographic Study. The measurements were carried out on a Rigaku Mercury CCD diffractometer at room temperature with graphite-monochromated Mo Kα (λ = 0.71075 Å) radiation. Xray crystallographic data were collected and processed using CrystalClear (Rigaku 2000).27 The structures were solved by direct methods using SHELXS-2014, and the refinement was performed against F2 using SHELXL-2014.28,29 All of the non-hydrogen atoms are refined anisotropically. The hydrogen atoms are positioned with idealized geometry and refined with fixed isotropic displacement parameters. Relevant crystal data, collection parameters, and refinement results can be found in Table S1. Device Fabrication and Photocurrent Measurement. The photodetector was fabricated as a simple Schottky device in an ambient atmosphere for 1 or 2. A layer of perovskite-like compound 1 or 2 was sandwiched in two indium−tin oxide (ITO) glasses. The perovskite layers were prepared by a solution-coating method. A N,Ndimethylformamide (DMF) solution containing 10 mg of 1 or 2 was drop-coated onto an ITO electrode in a 0.8 cm2 area at a temperature of 50 °C (about 100 μm thickness). An insulating diaphragm was used to ensure the fixed photoconductive area. A 150-W high-pressure xenon lamp, positioned 20 cm from the surface of the electrode, was employed as the light source. The photocurrent experiments were performed on a CHI650 electrochemistry workstation in a twoelectrode system.

Figure 1. (a) Solid-state UV−vis absorption spectra of 1 and 2, with inset photographs showing their appearance. (b) TGA curves of 1 and 2.

inserted photographs of the crystal samples. Band gaps estimated by extending the linear part of the absorption edge are 2.45 eV for 1 (yellow) and 2.15 eV for 2 (red). Thermal analysis showed that the compounds are stable below 280 °C and both compounds undergo two-step decomposition (Figure 1b). The first step of the decomposition of 1 happens at 320 °C and continues to 430 °C with a weight loss of 36.5%, which corresponds to the loss of three (H2Aepz)I2 (37.4%). Then PbI2 is sublimed vigorously over 500 °C. Similarly, the first step of the decomposition of 2 has a weight loss of 43.5%, which corresponds to the loss of one (H2Aepz)I2 (44.3%). Structural Characteristics. Compound 1 crystallizes in the triclinic P1̅ space group (Table S1). The Aepz molecule is bisprotonated on nitrogen atoms of the pyrazole and amine groups, which forms an organic dication. The asymmetric unit consists of one Pb2I73− unit and one and a half H2Aepz2+ cations (Figure S3a). The half H2Aepz2+ cation has not been solved, and only fragmentary atoms are located as a result of the cations surrounded with heavy lead atoms. Compound 1 is a two-layered hybrid lead halide. The H2Aepz2+ cations locate between the inorganic layers with alternating up and down configurations (Figure 2a,b). The noteworthy structural feature of 1 is the unusual connection mode of the PbI octahedra that is not the pure corner-sharing bilayer structure as those reported in bilayer compounds, such as (C6H5C2H4NH3)2(CH3NH3)Pb2I7 and (C4H3SCH2NH3)2(CH3NH3)Pb2I7,25,26 where the layer can be considered as being sliced from the 3D perovskite. As shown in Figure 2b, every two PbI octahedra in one layer are edge-shared to be a Pb2I10 dimer, and then the dimers are corner-shared with each other in an equatorial position to be a single layer with rectangular holes. Two of the single layers are further connected to a 2D sheet by cosharing

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RESULTS AND DISCUSSION Preparation and Characterization. Compounds 1 and 2 were prepared directly by one-step in situ solvothermal synthesis in a HI solution at 70 °C with different mole ratios B

DOI: 10.1021/acs.inorgchem.6b02550 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 3. Crystal structure of 2: (a) one-layered structure; (b) arrangement of the layers.

direction (Figure 3b). The H2Aepz2+ cations locate up and down alternatively between the inorganic layers with weak N− H···I hydrogen bonds (Figure S4b and Table S2). Photoelectroresponsive Properties. The energy levels of the valence and conduction bands of 1 and 2 are calculated from their onset potentials of the Eox peaks in CV experiments and their band gaps (Figure 4). They are similar to the band

Figure 2. Crystal structure of 1: (a) two-layered structure; (b) arrangement of PbI octahedra in one sheet; (c and d) cavities filled with disordered H2Aepz2+ cations.

the top iodine atoms. Larger cavities (compared with that of the classical perovskite structure) filled with disordered H2Aepz2+ cations are then formed (Figure 2c,d). The structure is a result of charge balance and self-assembles in order to fit with the size of the H2Aepz2+ cation. As far as we know, only small CH3NH3+ and CH(NH2)2+ can enter the layered structures. Compound 1 is an unusual example that the larger H2Aepz2+ cation enters into the perovskite-like layered structure. Aepz can be protonated to be a two positively charged cation H2Aepz2+, which is the advantage of Aepz being incorporated in the PbI layer. Although the inner H2Aepz2+ cannot be solved because of disorder, they are characterized by accurate CHN elemental and thermal analyses (Figure 1b). The finding of this structure gives us the imagination to look for new organic− inorganic hybrid perovskite-like materials with small functional organic cations. The asymmetric unit of 1 contains two independent lead(II) centers, and the two PbI octahedra are edge-shared as a Pb2I10 subunit, with Pb−I bond lengths ranging from 3.0582(13) to 3.2981(15) Å, while the axial I−Pb−I bond angles range from 172.59(4) to 177.82(4)°. All of these values are close to those reported PbI perovskites.17−26 The H2Aepz2+ cations locate between the inorganic layers with alternating up and down configurations. There are a lot of weak Nam−H···I and Npyr− H···I hydrogen bonds (am = amine; pyr = pyrazole) in crystal 1, which bridge the protonated cations with the lead−iodine inorganic layers (Figure S4a). It should be noted that the protonated amine group hydrogen bonds not only with terminal iodine atoms but also with bridged iodine atoms. The important hydrogen-bond distances and angles are listed in Table S2. Compound 2 crystallizes in the monoclinic P21/n space group (Table S1). The asymmetric unit consists of one PbI42− unit and one H2Aepz2+ cation (Figure S3b). The structure of 2 consists of perovskite-type one-layered sheets separated by organic divalent protonated Aepz cations, as encountered in hybrid compounds based on the A2PbI4 formula. As shown in Figure 3a, the lead ion is six-coordinated in an octahedral geometry. Each lead atom is coordinated by iodide atoms in a slightly distorted octahedral geometry, with Pb−I bond lengths ranging from 3.0633(13) to 3.3178(13) Å, while the axial I− Pb−I bond angles range from 171.02(4) to 175.98(2)°. Also, the Pb−I−Pb bond angles in the equatorial plane, 156.29(4)° and 178.08(5)°, indicate a rotation of adjacent polyhedra in the sheet, which is well-known in hybrid perovskites.18−25 The neighboring perovskite layers have a shift along the [1, 0, −1]

Figure 4. Energy levels of the valence and conduction bands of 1 and 2 along with the band energy levels of the typical perovskite.

energy levels of layered perovskites.13 The compounds are potential photoactive materials as MAPbI3. A photoelectroresponsive device was designed. As shown in Figure S5, a simple Schottky device as the photodetector was fabricated, in which a layer of the perovskite-like compound 1 or 2 was sandwiched in two ITO glasses. The layers of 1 or 2 were obtained by a solution-coating method. An insulating diaphragm was used to ensure the fixed photoconductive area. Figure 5 shows the SEM images of the surface morphology of 1- and 2-coated films using a DMF solution. The films are uniform in appearance with fused microrod-like crystals that are more obvious for the

Figure 5. SEM images of the surface morphology of the 1-coated (a and b) and 2-coated (c and d) films using a DMF solution. C

DOI: 10.1021/acs.inorgchem.6b02550 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry film of 2. The microcrystals are about 0.5−1.0 μm wide and 5− 10 μm long. Therefore, high-quality films of the compounds can be easily obtained. The films of 1 and 2 are stable in an ambient atmosphere for a long time unlike MAPbI3, which is moisture-sensitive and must be preserved in vacuum. Figure S6 gives spectra of the films of these three compounds before and after exposure in an ambient atmosphere. The color of MAPbI3 changes to yellow quickly, but those of 1 and 2 are not changed over 1 month. The photocurrent responsive properties of the devices were examined upon on and off irradiation with xenon light (150 W; Figure 6). Photocurrent responses happened quickly without

Figure 7. Photocurrent densities of 1 and 2 compared with that of the typical organic−inorganic hybrid perovskite MAPbI3.

Figure 6. Photocurrent responsive properties of the devices of 1 (a and b) and 2 (c and d) recorded under 0 V (a and c) and 1.0 V (b and d) bias potentials.

delay with stable intensity. This demonstrates the high responsive ability and the repeatability of the photodetectors. The data of the current density were recorded under 0 and 1.0 V bias potentials. Under 0 and 1.0 V bias potentials (Figure 6a,b), the current densities of the device of 1 are 0.016 and 0.22 μA/cm2, respectively, whereas those of the device of 2 are 0.48 and 4.80 μA/cm2 (Figure 6c,d), respectively. The data show a series increment, where (1) the current density of 2 is about 10 times that of 1 and (2) the current density measured under the 1.0 V bias potential is 10 times that measured under the 0.0 V bias potential for both 1 and 2. In general, the band gap is decreased with an increase in the perovskite layers.31 It is somewhat unbelievable that the photocurrent density of two-layered compound 1 is smaller than that of 2. The result originates from the discontinuity within the layered structure of 1 (a cavity filled with an electroinactive organic cation), which causes an increase in the band gap. Figure 7 shows the related current densities of 1 and 2 compared with that of the typical organic−inorganic hybrid perovskite MAPbI3. The density of the one-layered compound 2 is about 1/2 times that of MAPbI3, and the reason has been explained by the larger band gap due to spatial confinement of the excitons in a 2D structure.12,13 A similar reason is regarded for the lower current density of 1. First-principle calculations of the density of states (DOS) of the inorganic layers of 1 and 2 were carried out using the CASTEP code implemented in the Materials Studio 4.0 package,32 and the results are plotted in Figure 8. In both

Figure 8. Calculated total and projected DOSs for (a) 1 and (b) 2.

compounds, the main atomic states found in the region of the valence-band maximum are I 5p orbitals, with a small contribution from Pb 6s. The calculated band gap of 1 is 2.30 eV, while that of 2 is 1.8 eV, in approximate agreement with those obtained in the spectra. The organic-cationtemplated large cavities cause a dielectric mismatch between the organic and inorganic structures. The mechanism for photocurrent generation can be explained by a two-junction opposite-directional device model.33,34 When irradiated with light from the left to the ITO glass of the device (Figure S6), electron−hole pairs are generated in the left depletion zone (ITO/perovskite junction). The photoelectrons move to the left conductive band of the electrode, and the photogenerated holes in the valence band move through perovskite to the right depletion zone. As a result, the right electrode is electropositive, which is apt to attract electrons that travel from left to right through the external circuit.

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CONCLUSIONS In summary, as far as we know, only small CH3NH3+ or CH(NH2)2+ cations can incorporate into the multilayered D

DOI: 10.1021/acs.inorgchem.6b02550 Inorg. Chem. XXXX, XXX, XXX−XXX

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Hagfeldt, A.; Grätzel, M.; Segawa, H. Spectral splitting photovoltaics using perovskite and widebanddye-sensitized solar cells. Nat. Commun. 2015, 6, 8834. (6) Stoumpos, C. C.; Malliakas, C. D.; Kanatzidis, M. G. Semiconductingtin and lead iodide perovskites with organic cations: phase transitions, highmobilities, and near-infrared photoluminescent properties. Inorg. Chem. 2013, 52, 9019−9038. (7) Pellet, N.; Gao, P.; Gregori, G.; Yang, T.-Y.; Nazeeruddin, M. K.; Maier, J.; Grätzel, M. Mixed-organic-cationperovskitephotovoltaics for enhancedsolar-light harvesting. Angew. Chem., Int. Ed. 2014, 53, 3151− 3157. (8) Chen, Q.; Zhou, H.; Hong, Z.; Luo, S.; Duan, H.-S.; Wang, H.H.; Liu, Y.; Li, G.; Yang, Y. Planar heterojunctionperovskite solar cells via vapor-assistedsolution process. J. Am. Chem. Soc. 2014, 136, 622− 625. (9) Dohner, E. R.; Hoke, E. T.; Karunadasa, H. I. Self-assembly of broad band white-light emitters. J. Am. Chem. Soc. 2014, 136, 1718− 1721. (10) Tsuei, C. C.; Gupta, A.; Trafas, G.; Mitzi, D. Superconducting mercury-based cuprate films with a zero-resistance transition temperature of 124 K. Science 1994, 263, 1259−1261. (11) Smith, I. C.; Hoke, E. T.; Solis-Ibarra, D.; McGehee, M. D.; Karunadasa, H. I. A layered hybrid perovskite solar-cell absorber with enhancedmoisture stability. Angew. Chem., Int. Ed. 2014, 53, 11232− 11235. (12) Dou, L.; Wong, A. B.; Yu, Y.; Lai, M.; Kornienko, N.; Eaton, S. W.; Fu, A.; Bischak, C. G.; Ma, J.; Ding, T.; Ginsberg, N. S.; Wang, L.W.; Alivisatos, A. P.; Yang, P. Atomically thin two-dimensional organic-inorganic hybridperovskites. Science 2015, 349, 1518−1521. (13) Cao, D. H.; Stoumpos, C. C.; Farha, O. K.; Hupp, J. T.; Kanatzidis, M. G. 2D homologous perovskites as light-absorbing materials for solar cellapplications. J. Am. Chem. Soc. 2015, 137, 7843− 7850. (14) Mitzi, D. B.; Feild, C. A.; Harrison, W. T. A.; Guloy, A. M. Conducting tin halides with a layered organic-based perovskite structure. Nature 1994, 369, 467−469. (15) Mitzi, D. B.; Wang, S.; Feild, C. A.; Chess, C. A.; Guloy, A. M. Conducting Layered Organic-inorganic Halides Containing < 110>Oriented Perovskite Sheets. Science 1995, 267, 1473−1476. (16) Calabrese, J.; Jones, N. L.; Harlow, R. L.; Herron, N.; Thorn, D. L.; Wang, Y. Preparation and characterization of layered lead halide compounds. J. Am. Chem. Soc. 1991, 113, 2328−2330. (17) Billing, D. G.; Lemmerer, A. Synthesis, characterization and phasetransitions in the inorganic-organic layered perovskite-type hybrids [(CnH2n+1NH3)2PbI4], n = 4, 5 and 6. Acta Crystallogr., Sect. B: Struct. Sci. 2007, 63, 735−747. (18) Billing, D. G.; Lemmerer, A. Inorganic-organic hybrid materials incorporating primary cyclic ammonium cations: The lead iodide series. CrystEngComm 2007, 9, 236−244. (19) Pradeesh, K.; Baumberg, J. J.; Prakash, G. V. In situ intercalation strategies for device-quality hybrid inorganic-organic self-assembled quantum wells. Appl. Phys. Lett. 2009, 95, 033309. (20) Lemmerer, A.; Billing, D. G. Effect of heteroatoms in the inorganic organic layered perovskite-type hybrids [(ZCnH2nNH3)2PbI4], n = 2, 3, 4, 5, 6; Z = OH, Br and I; and [(H3NC2H4S2C2H4NH3)PbI4]. CrystEngComm 2010, 12, 1290−1301. (21) Lemmerer, A.; Billing, D. G. Synthesis, characterization and phase transitions of the inorganic-organic layered perovskite-type hybrids [(CnH2n+1NH3)2PbI4], n = 7, 8, 9 and 10. Dalton Trans. 2012, 41, 1146−1157. (22) Tang, Z.; Guan, J.; Guloy, A. M. Synthesis and crystal structure ofnew organic-based layered perovskites with 2,2-biimidazolium cations. J. Mater. Chem. 2001, 11, 479−482. (23) Xu, Z.; Mitzi, D. B.; Medeiros, D. R. [(CH3)3NCH2CH2NH3]SnI4: A layered perovskite with quaternary/primary ammonium dications and short interlayer iodine-iodine contacts. Inorg. Chem. 2003, 42, 1400−1402. (24) Weber, O. J.; Marshall, K. L.; Dyson, L. M.; Weller, M. T. Structural diversity in hybrid organic−inorganic lead iodide materials.

perovskite structure. We obtained recently a two-layered perovskite-like lead iodide (1) in which large cavities are formed by a partial change of the corner-shared link mode of PbI6 octahedra in perovskite to the edge-shared mode. It is an unusual example that a large organic cation was incorporated in an inorganic PbI perovskite-like structure. Another 2D compound (2) was also prepared that is a one-layer perovskite. The photoelectroresponsive properties of the compounds were compared with that of a typical organic−inorganic hybrid perovskite (CH3NH3)PbI3. The current density is in the order of two-layered 1 < one-layered 2 < (CH3NH3)PbI3, in agreement with the order of the band-gap change. The results of the lower current density and larger band energy of 1 originate from its discontinuity within the layered structure caused by the organic-cation-templated large cavities. Anyway, the structure of 1 is a new type of perovskite-like topology. If the embeded organic cation is replaced by a photoelectroactive one, new organic−inorganic hybrid materials with excellent efficiency for solar energy transfer are expected.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b02550. Powder XRD, IR, asymmetric units, hydrogen-bonding interactions, a schematic view of the device, and current densities of 1, 2, and (CH3NH3)PbI3 (PDF) CIF file for 1 (CCDC 1506822) (CIF) CIF file for 2 (CCDC 1506823) (CIF)

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Qin-Yu Zhu: 0000-0003-1864-1175 Jie Dai: 0000-0002-3549-726X Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We gratefully acknowledge financial support by the NSF of China (21371125, 21571136), the Priority Academic Program Development of Jiangsu Higher Education Institutions, and by State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials.

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REFERENCES

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DOI: 10.1021/acs.inorgchem.6b02550 Inorg. Chem. XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.inorgchem.6b02550 Inorg. Chem. XXXX, XXX, XXX−XXX