Excitonic Effects in Methylammonium Lead Halide Perovskites

Chen, Xihan; Lu, Haipeng; Yang, Ye; Beard, Matthew C.

doi:10.1021/acs.jpclett.8b00526

Cited by 123 publications

(137 citation statements)

References 64 publications

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“…Most studies showed that the excitons, if formed at room temperature, dissociated rapidly into free carriers on a sub‐ps time scale, leading to the free carriers dominating in the subsequent processes . However, researchers also revealed that excitonic effects play an important role in defining the optical properties of MHPs since their band edge absorption onsets as well as the transient absorption spectra were found to be dominated by the exciton resonances . Meanwhile, the current prevailing view prefers a branch between the free carriers and excitons after photoexcitation, with one of the two species dominating under appropriate conditions and determining their photophysical properties as well as applications.…”

Section: Introductionmentioning

confidence: 99%

Properties of Excitons and Photogenerated Charge Carriers in Metal Halide Perovskites

2019

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their great success in photovoltaics (PVs), with a phenomenally rapid rise of the power conversion efficiency (PCE) from 3.8% [1] to over 23% [2,3] in the past few years. Such high PCE of perovskite solar cells has been ascribed to the ultralong carrier lifetimes, [4][5][6][7][8] long carrier diffusion lengths, [9][10][11][12][13][14] and the extraordinarily defect tolerance. [15][16][17] Following the success of perovskites in photovoltaics, research on light-emitting diodes (LEDs), [18,19] amplified spontaneous emission (ASE) or lasers, [20][21][22][23][24] and photodetectors [25][26][27][28][29] have also gained substantial interests. Meanwhile, the rapid progress of MHPs on various applications spurred a flurry of photophysical studies in order to understand the origin of the high performance of these devices, of which the nature of the photoexcitation species has been mostly debated. [5,22,30,31] Since the photoexcitation states near the bandgap affect the key processes such as charge transport and light emission of optoelectronic devices, there is no doubt that the investigation of electronic excitations near the optical band edge is crucial for MHPs. Such knowledge is essential not only for understanding the correlation between the fundamental photophysics and device performances, but also offering a guideline for their further applications with improved performances. Generally, there are two kinds of photoexcitations near the band edge for direct bandgap semiconductors: free carriers and excitons. Exciton binding energy that reflects the Coulomb interaction strength between photoexcited electrons and holes determines the balance of the populations between the two species. Typically, inorganic semiconductors are free-carrier materials with the exciton binding energies only in few meV at room temperature and their excited states being populated principally by free carriers. While organic semiconductors are excitonic materials with the exciton binding energies in hundreds of meV and thus excitons prevailing in the excited states. Whereas, MHPs that combine some merits of organic and inorganic semiconductors seem to stand for an exotic class of semiconductors between these two limiting cases, with the experimentally determined exciton binding energy varying in a wide range of 2 to more than 50 meV for the prototype perovskite MAPbI 3 . [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] Such large variations of the exciton binding energies reported for MHPs give rise to a strongly debated question, that is, whether free carriers or excitons are generated upon photoexcitation? In other words, what is the nature of the photoexcitation species Metal halide perovskites (MHPs) have recently attracted great attention from the scientific community due to their excellent photovoltaic performance as well as their tremendous potential for other optoelectronic applications such as light-emitting diodes, lasers, and photodetectors. Despite the rapid progress in device applications, a solid unders...

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Section: Introductionmentioning

confidence: 99%

Properties of Excitons and Photogenerated Charge Carriers in Metal Halide Perovskites

2019

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“…Previous studies have shown that OSE characterizes the splitting of the double spin degenerate ground states and offers a great chance to introduce microscale lightmatter interactions. [130] The transient absorption spectra during the Stark effect show considerable differences in the pumpprobe results of a diverse range of polarization configurations, thus indicating an entangle ment of excitonic states. These results will aid in the analysis of how Coulomb interactions between the photogenerated electrons and holes affect the photoelectric performance.…”

Section: Large Stark Effectmentioning

confidence: 99%

“…Research with a focus on excitons has played an important part in studying the Stark effect and spin‐related electro‐optical interactions. Previous studies have shown that OSE characterizes the splitting of the double spin degenerate ground states and offers a great chance to introduce microscale light‐matter interactions . The transient absorption spectra during the Stark effect show considerable differences in the pump‐probe results of a diverse range of polarization configurations, thus indicating an entanglement of excitonic states.…”

Section: Novel Spin‐related Physical Effects Arising From Hopsmentioning

confidence: 99%

Spintronics of Hybrid Organic–Inorganic Perovskites: Miraculous Basis of Integrated Optoelectronic Devices

Liao

Cheng

et al. 2019

Advanced Optical Materials

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Hybrid organic–inorganic perovskite (HOP) spintronics aims to make full use of the properties of electron spin. HOP spintronics has recently emerged as a promising field of research because it provides a new precisely manipulable degree of freedom. The flourishing development activity in this field has benefited from the unique intrinsic spin‐related optoelectronic properties of HOPs, which include triplet formation, a large Stark effect, the magneto‐optical effect, polarized light‐related effects, and complex light emission characteristics, which offer the possibility of providing a new way to control the performance of integrated optoelectronic devices through spin interactions between photons and electrons. Along with the continuous improvements in the theoretical research into HOP spintronics, large numbers of novel optoelectronic devices have been proposed and demonstrated experimentally and have shown great potential for fabrication of next‐generation, high‐performance integrated optoelectronic chips. This review provides an overview of the fundamental principles, novel spin‐generated physical effects, and diverse structures of HOP spintronics systems, along with the applications of HOP spintronics in optoelectronic devices, while also undertaking a general review of the remaining challenges and proposing possible development directions that require further study for the application of HOP spintronics to integrated optoelectronic devices.

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“…Previously, a number of studies have studied the physical behavior of 3D hybrid halide perovskites under extreme hydrostatic pressures using diamond anvil cell (DAC) chamber design . These pressure studies provide a powerful tool for changing interatomic distances and bond lengths on demand, and monitor structural, physical, or chemical properties and functionalities at finite pressures.…”

Section: Summary Of Experimental and Theoretical Bandgap Values For 2mentioning

confidence: 99%

“…[12,13] Previously, a number of studies have studied the physical behavior of 3D hybrid halide perovskites under extreme hydrostatic pressures using diamond anvil cell (DAC) chamber design. [14][15][16][17][18][19][20] These pressure studies provide a powerful tool for changing interatomic distances and bond lengths on demand, and monitor structural, physical, or chemical properties and functionalities at finite pressures. Indeed DAC pressure studies on some of 3D hybrid halide materials to date have enabled new discoveries such as novel structural phase transitions and PbBr 6 octahedra distortions.…”

mentioning

confidence: 99%

Unusual Pressure‐Driven Phase Transformation and Band Renormalization in 2D vdW Hybrid Lead Halide Perovskites

Qin

Shan

et al. 2020

Advanced Materials

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The application of high pressure allows control over the unit cell and interatomic spacing of materials without any need for new growth methods or processing while accessing their materials properties in situ. Under these extreme pressures, materials may assume new structural phases and reveal novel properties. Here, unusual phase transition and band renormalization effects in 2D van der Waals Ruddlesden−Popper hybrid lead halide perovskites, which have shown extraordinary optical properties and immense potential in light emission and conversion technologies, are reported. The results show that (CH3(CH2)3NH3)2(CH3NH3)Pb2Br7 (n = 2) layers undergo two distinct phase transitions related to PbBr6 octahedra, butylammonium (BA), and methylammonium (MA) molecule tilting motion that leads to rather unique/anomalous bandgap variation with pressure. In contrast, (CH3(CH2)3NH3)PbBr4 (n = 1) lacks MA molecules and possesses only one pressure‐induced phase transition related to PbBr6 octahedra and BA tilting. In this range, the bandgap reduces monotonically, much similar to other inorganic semiconductors and display surprisingly large redshift from 3 to 2.4 eV. Together with theoretical calculations, this study offers unique insights into these pressure‐induced changes and extends the understanding of these highly anisotropic layered soft organic perovskite materials under extreme conditions.

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Excitonic Effects in Methylammonium Lead Halide Perovskites

Cited by 123 publications

References 64 publications

Properties of Excitons and Photogenerated Charge Carriers in Metal Halide Perovskites

Properties of Excitons and Photogenerated Charge Carriers in Metal Halide Perovskites

Spintronics of Hybrid Organic–Inorganic Perovskites: Miraculous Basis of Integrated Optoelectronic Devices

Unusual Pressure‐Driven Phase Transformation and Band Renormalization in 2D vdW Hybrid Lead Halide Perovskites

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