Comparative study on the excitons in lead-halide-based perovskite-type crystals CH3NH3PbBr3 CH3NH3PbI3

Tanaka, Kenichiro; Takahashi, Takayuki; Ban, Takahiko; Kondo, Takashi; Uchida, K.; Miura, N.

doi:10.1016/s0038-1098(03)00566-0

Cited by 875 publications

(894 citation statements)

References 19 publications

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“…The question as to which optically excited species may couple to the THz probe pulse, either excitons or free charge-carriers has been addressed several times in earlier reports. [ 17,18,[39][40][41][42] We note that for MAPbI 3 the sole response to the THz conductivity probe has already been shown to be that of a free-charge carrier density, as inferred from the Drude shape of the conductivity spectra. [ 17,18 ] Here we also report highly similar Drude conductivity spectra for FAPbBr 3 (see the Supporting Information), which suggests that excitonic effects are negligible at room temperature for these mixed I/Br materials.…”

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confidence: 69%

Charge‐Carrier Dynamics and Mobilities in Formamidinium Lead Mixed‐Halide Perovskites

et al. 2015

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by at least four orders of magnitude. [ 17,18 ] MAPbI 3 also appears to exhibit only shallow trap-levels and although the grain boundaries have recently been shown to induce nonradiative decay, [ 19 ] regions only a few tens of nm away from the grain boundaries appear to be unaffected. [ 20,21 ] Furthermore, low Urbach energies, which are extracted from near band edge optical absorption measurements and serve as a benchmark for crystalline phase disorder, indicate low disorder and sharp band edges for lead tri-halide perovskites (15-23 meV). [ 22,23 ] All of these properties contribute to high open-circuit voltages, long charge-carrier lifetimes, and micrometer diffusion lengths, which are crucial for planar-hetero junction photovoltaics. [ 1,24 ] Nonetheless, these parameters are also expected to depend on the infl uence of crystallization condition on perovskite morphology in fabricated fi lms. [ 25 ] A distinct benefi t of organic-inorganic perovskite materials (e.g., over silicon) is that their bandgap can be tuned relatively easily with chemical composition, allowing attractive coloration and multijunction or tandem cell designs. For example, changing the metal cation at the M site from Pb 2+ to the less toxic Sn 2+ to form CH 3 NH 3 SnI 3 shifts the optical bandgap from 1.55 to 1.3 eV into the range of the "ideal" single-junction solar cell bandgap between 1.1 and 1.4 eV. [ 26,27 ] However, stability issues arising from the oxidation of tin have so far prevented widespread use. Alternatively, tuning the size of the A site cation has been proven to change optical and electronic properties of the perovskite and to signifi cantly infl uence solar cell performance. [ 28 ] Replacing MA in MAPbI 3 by the larger cation formamidinium HC(NH 2 ) 2 + (FA) was found to decrease the bandgap from 1.57 to 1.48 eV, [29][30][31] yield long photoluminescence (PL) lifetimes, high PCEs, [ 28 ] and lower recombination and device hysteresis. [ 32 ] Highest PCEs of 20.1% have been reported [12][13][14] to date for solar cells based on FAPbI 3 making this an attractive system to explore. In addition, the gradual replacement of the MA cation by FA through the fi lm was shown to create a mixed cation-lead-iodide PSC allowing for energetic gradients. [ 33 ] However, mixing of the halide component in the perovskite offers the fi nest tuning of the optical properties of the perovskite fi lm. Here, the mixed organic lead iodide/bromide system has recently gained strong interest for application in PSCs. [ 11,28 ] By changing the ratio between bromide and iodide (at the X site anion), the bandgap can be tailored between 1.55 eV (MAPbI 3 ) and 2.3 eV (MAPbBr 3 ), which results in the coverage of much of the visible spectrum and paves the way for the development of tandem solar cells. [ 11 ] In addition to MAPb(Br y I 1-y ) 3 , its formamidinium relative FAPb(Br y I 1-y ) 3 has been explored. [ 28 ] Most fractional mixtures of FAPb(Br y I 1-y ) 3 were found to be crystalline, with the exception of the region between y = 0.3 and Recent year...

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confidence: 69%

Charge‐Carrier Dynamics and Mobilities in Formamidinium Lead Mixed‐Halide Perovskites

et al. 2015

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“…In turn, the absorption edge is blue-shifted by about 10 nm for CH 3 NH 3 PbBr 3 wires and plates compared to bulk CH 3 NH 3 PbBr 3 ( Figure 12). The specific apparent band gaps, measured from the absorption data using Tauc plots ((Ahν) 2 vs hν for a direct band gap semiconductor, where A = absorption coefficient, hν = energy of light) were 1.56 eV for bulk CH 3 61 It is worth noting that some references have attributed a narrowing in the optical band gap of larger organometal halide perovskite crystals to changes in the degree of PbÀI bond stress. 62 An interesting characteristic of organometal perovskite semiconductors is that they are good fluorophores and can be highly emissive.…”

Section: Resultsmentioning

confidence: 99%

Shape Evolution and Single Particle Luminescence of Organometal Halide Perovskite Nanocrystals

et al. 2015

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Organometallic halide perovskites CH 3 NH 3 PbX 3 (X = I, Br, Cl) have quickly become one of the most promising semiconductors for solar cells, with photovoltaics made of these materials reaching power conversion efficiencies of near 20%. Improving our ability to harness the full potential of organometal halide perovskites will require more controllable syntheses that permit a detailed understanding of their fundamental chemistry and photophysics. In this manuscript, we systematically synthesize CH 3 NH 3 PbX 3 (X = I, Br) nanocrystals with different morphologies (dots, rods, plates or sheets) by using different solvents and capping ligands. CH3NH3PbX3 nanowires and nanorods capped with octylammonium halides show relatively higher photoluminescence (PL) quantum yields and long PL lifetimes. CH3NH3PbI3 nanowires monitored at the single particle level show shape-correlated PL emission across whole particles, with little photobleaching observed and very few off periods. This work highlights the potential of low-dimensional organometal halide perovskite semiconductors in constructing new porous and nanostructured solar cell architectures, as well as in applying these materials to other fields such as light-emitting devices and single particle imaging and tracking.Keywords organometal halide perovskites, nanocrystals, preferred orientation, morphology control, size control, single particle photoluminescence Disciplines Chemistry CommentsReprinted (adapted) with permission from ACS Nano 9 (2015) 15,16 respectively, as well as high absorption coefficients. Critically, organolead perovskites have very long electronÀ hole carrier diffusion lengths, exceeding 1 μm in CH 3 NH 3 PbI 3-x Cl x , and 100 nm in CH 3 NH 3 PbI 3 , which in principle allows for the development of several solar cell architectures including perovskite-sensitized solar cells, planar heterojunction solar cells, and meso-and nanostructured solar cells. 17 Building on the dramatic improvement of solar cell performance using the solid hole conductor spiro-OMeTAD instead of a liquid electrolyte (spiro-OMeTAD stands for 2,2 0 -7,7 0 -tetrakis(N,N-di-p-methoxy-phenylamine)-9,9 0 -spirobifluorene), 18 the energy conversion efficiency of photovoltaics made from these intensely absorbing, visible-active semiconductors has risen from 3.8% to near 20% in only four years. 19,20 Photovoltaic performance depends critically on perovskite composition, crystallinity and morphology. 21À23 Higher perovskite film uniformity leads to lower recombination rates in planar heterojuction solar cells. 24,25 Film uniformity is affected by factors such as precursor composition, annealing temperature and, if applicable, solvent used during the vapor-assisted or spin coating deposition process. 6,24,26À32 Highly efficient mesostructured solar cells are produced by a twostep deposition process. 33À35 Vapor-assisted methods and additives provide the means * Address correspondence to jwp@iastate.edu, esmith1@iastate.edu, vela@iastate.edu.Received for review December 9, 2014 a...

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“…Since this behavior is essentially the same with (C 6 H 13 NH 3 ) 2 PbI 4 , the bandgap of bilayer is determined to be at 2.40 eV, from which the binding energy of the lowest-energy exciton are obtained to be 260 meV. Although the obtained binding energy of the lowest-energy excitons are smaller than that in monolayer (361 meV [15]), it is at least five times as large as that of the lowest-energy excitons in the 3D crystal, CH 3 NH 3 PbI 3 (50 meV [17]). Since the spatial quantum confinement only quadruples the exciton binding energy in the 2D limit, this strong enhancement factor (.5) indicates that the image charge effect plays an additional role in the drastic enhancement of the excitons binding energy.…”

Section: Optical Absorptionmentioning

confidence: 92%

“…Optical absorption spectra of (a) (C 6 absorption spectra of bilayer and trilayer spin-coated films at 5 K. In these optical absorption spectra, any abrupt leaps of the optical absorption spectra with decreasing temperature like those of (C 10 H 21 NH 3 ) 2 PbI 4 [3] are not observed. The optical absorption spectrum of the 3D thin film [17] is shown in Fig. 1(d), for comparison.…”

Section: Methodsmentioning

confidence: 99%

“…The three-dimensional (3D) analogue CH 3 NH 3 PbI 3 [17] corresponds to the case m ¼ 1: Since the thickness of the inorganic layers can be controlled by changing m; systematic studies of the excitonic and electronic properties between the 2D and 3D crystals can be performed. In this study, we have made a optical absorption and electroabsorption (EA) study on this 2D -3D crystal group, and will present the results of the comparative study on these 2D -3D crystals.…”

Section: Introductionmentioning

confidence: 99%

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Bandgap and exciton binding energies in lead-iodide-based natural quantum-well crystals

Tanaka¹,

Kondo

2003

Science and Technology of Advanced Materials

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153

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We have performed optical absorption and electroabsorption studies on the lead-iodide-based natural quantum-well perovskite-type crystals with different well width (C 6 H 13 NH 3 ) 2 (CH 3 NH 3 ) m21 Pb m I 3mþ1 . With decreasing well thickness, m; the resonance energies of the lowest-energy excitons shift to higher energy due to the increase of the bandgap. The binding energies and oscillator strengths of the excitons drastically increase due to the spatial confinement and image charge effect with decreasing m: The bandgap of (C 6 H 13 NH 3 ) 2 (CH 3 NH 3 ) m21-Pb m I 3mþ1 ðm $ 2Þ can be reproduced by the effective-mass approximations, while the effective-mass approach is not valid for (C 6 H 13 NH 3 ) 2 PbI 4 ðm ¼ 1Þ: q

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Comparative study on the excitons in lead-halide-based perovskite-type crystals CH3NH3PbBr3 CH3NH3PbI3

Cited by 875 publications

References 19 publications

Charge‐Carrier Dynamics and Mobilities in Formamidinium Lead Mixed‐Halide Perovskites

Charge‐Carrier Dynamics and Mobilities in Formamidinium Lead Mixed‐Halide Perovskites

Shape Evolution and Single Particle Luminescence of Organometal Halide Perovskite Nanocrystals

Bandgap and exciton binding energies in lead-iodide-based natural quantum-well crystals

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