Observation of a hot-phonon bottleneck in lead-iodide perovskites

Yang, Ye; Ostrowski, David P.; Zhu, Kai; Lagemaat, Jao van de; Luther, Joseph M.; Beard, Matthew C.

doi:10.1038/nphoton.2015.213

Cited by 800 publications

(1,218 citation statements)

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“…As an example, the electronic single particle gap of MAPbI 3 has been measured as 1.7±0.1 eV, compared to an optical bandgap of 1.65 eV and 9-17 meV exciton binding energy matching the predictions from GW calculations with corrections for spin-orbit coupling (1.67 eV). 163,175,176 An improvement to this evaluation can be achieved by carefully lining up the experimentally obtained spectra from PES and IPES measurements with simulated spectra from DFT calculations, as described above and demonstrated in Figure 8. A significant refinement of the band onset determination for a range of hybrid perovskite films was reported by Endres et al Therein, the electrical bandgap for MAPbI 3 was determined to be 1.6±0.1 eV, 177 in agreement with optical measurements, 175 and demonstrating greater accuracy than previous electronic bandgap measurements that did not make use of DOS fitting of the IPES spectra.…”

Section: Complementary Techniques To Photoemission Spectroscopymentioning

confidence: 99%

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

et al. 2017

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ABSTRACT:Recently, there has been an explosive growth in research based on hybrid lead-halide perovskites for photovoltaics owing to rapid improvements in efficiency. The advent of these materials for solar applications has led to widespread interest in understanding the key enabling properties of these materials. This has resulted in renewed interest in related compounds and a search for materials that may replicate the defect-tolerant properties and long lifetimes of the hybrid lead-halide perovskites. Given the rapid pace of development of the field, the rises in efficiencies of these systems have outpaced the more basic understanding of these materials. Measuring or calculating the basic properties, such as crystal/electronic structure and composition, can be challenging because some of these materials have anisotropic structures, and/or are composed of both heavy metal cations and volatile, mobile, light elements. Some consequences are beam damage during characterization, composition change under vacuum, or compound effects, such as the alteration of the electronic structure through the influence of the substrate. These effects make it challenging to understand the basic properties integral to optoelectronic operation. Compounding these difficulties is the rapid pace with which the field progresses. This has created an ongoing need to continually evaluate best practices with respect to characterization and calculations, as well as to identify inconsistencies in reported values to determine if those inconsistencies are rooted in characterization methodology or materials synthesis. This article describes the difficulties in characterizing hybrid lead-halide perovskites and new materials, and how these challenges may be overcome. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 challenges discussed. The focus in this article is on crystallography, composition measurements, photoemission spectroscopy and calculations on perovskites and new, related absorbers. We suggest how some of the important artifacts could be avoided and how the reporting for each technique could be streamlined between groups to ensure reproducibility as the field progresses.

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Section: Complementary Techniques To Photoemission Spectroscopymentioning

confidence: 99%

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

et al. 2017

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“…In particular, inorganic/organic PSCs of ABX3 (A = Cs+, CH3NH3+, etc. ; B = Pb2+; X = Cl-, Br-or I-) show extraordinary solar cell efficiencies exceeding 22 % [1] with unusual characteristics, [2][3][4] which attracts tremendous attention as most promising large-scale solar energy conversion materials.[5] One key origin of high efficiency arises from high carrier mobility (µ) 10 -8] even in the presence of defects.[9] While the carrier transport exhibits remarkable features in experiments, there is still a gap of understanding. One aspect of this difficulty stems from significant electron-phonon (e-ph) interactions, [2,8,[10][11][12][13] which complicates band pictures.…”

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“…[9] While the carrier transport exhibits remarkable features in experiments, there is still a gap of understanding. One aspect of this difficulty stems from significant electron-phonon (e-ph) interactions, [2,8,[10][11][12][13] which complicates band pictures. Another aspect is due to the A-site cation that rotates [14] or even diffuses across the material, causing I-V hysteresis.…”

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A New Perspective on the Role of A‐Site Cations in Perovskite Solar Cells

Myung

Yun

Lee

et al. 2018

Advanced Energy Materials

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As the race towards higher efficiency for inorganic/organic hybrid perovskite solar cells (PSCs) is becoming highly competitive, a design scheme to maximize carrier transport towards higher power efficiency has been urgently demanded. Here, we unravel a hidden role of A-site cation of PSCs in carrier transport which has been largely neglected, i.e., tuning the Frhlich electron-phonon (e-ph) coupling of longitudinal optical (LO) phonon by A-site cations. The key for steering Frhlich polaron is to control the interaction strength and the number of proton (or lithium) coordination to halide ion. The coordination to I − alleviates electron-phonon scattering by either decreasing the Born effective charge or absorbing the LO motion of I. This novel principle discloses lower electron-phonon coupling by several promising organic cations including hydroxyl-ammonium cation (NH3OH + ) and possibly Li + solvating methylamine (Li + ···NH2CH3) than methyl-ammonium cation. A new perspective on the role of A-site cation could help in improving power efficiency and accelerating the application of PSCs.Solar energy is a highly efficient and eco-friendly source for future energy harvesting. In particular, inorganic/organic PSCs of ABX3 (A = Cs+, CH3NH3+, etc.; B = Pb2+; X = Cl-, Br-or I-) show extraordinary solar cell efficiencies exceeding 22 % [1] with unusual characteristics, [2][3][4] which attracts tremendous attention as most promising large-scale solar energy conversion materials.[5] One key origin of high efficiency arises from high carrier mobility (µ) 10 -8] even in the presence of defects.[9] While the carrier transport exhibits remarkable features in experiments, there is still a gap of understanding. One aspect of this difficulty stems from significant electron-phonon (e-ph) interactions, [2,8,[10][11][12][13] which complicates band pictures. Another aspect is due to the A-site cation that rotates [14] or even diffuses across the material, causing I-V hysteresis.[15] Although recent discovery of various types of cations has greatly advanced the efficiency of PSCs, [16] it also has brought about more ambiguity on the role of cations.In general, electrons in polar crystal experience the deformation potential in addition to Bloch potential due to large polarity of ionic bonding. The charge carriers are then described by polaron quasiparticles originating from coupling between electrons and phonons. For PSCs, there has been a critical debate on the source of e-ph coupling, acoustic vs. longitudinal. From the temperature dependence of µ ∼ T −3/2 around room temperature, acoustic phonons have been considered as the main source of e-ph coupling. [11,17] In this study, we unveil a hidden role of A-site cation in polaron picture of PSCs by accounting for the e-ph interactions regarding both A-site cation and LO phonon scattering at the first principles level. [18,19] We used the Frohlich polaron model [23] which is suitable for large bandwidth (W ) limit W ω ph by considering Frohlich vertex. [24] We cast light on the role o...

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Femtosecond Pump–Probe Spectroscopy for Organic Photovoltaic Devices

Raavi

Biswas

2019

Digital Encyclopedia of Applied Physics

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Charge photogeneration by exciton dissociation at the donor/acceptor interface is the heart of organic molecule–based devices for solar energy conversion. Femtosecond pump–probe spectroscopy offers a noninvasive technique to follow the charge photogeneration. In this article, we elucidate the contribution of femtosecond pump–probe spectroscopy in providing in‐depth insights into various photophysical aspects that aid in the development of efficient organic molecule–based solar cells, namely, dye‐sensitized solar cells, organic–inorganic hybrid solar cells, polymer‐based bulk heterojunction solar cells, and perovskite solar cells.

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Observation of a hot-phonon bottleneck in lead-iodide perovskites

Cited by 800 publications

References 42 publications

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

A New Perspective on the Role of A‐Site Cations in Perovskite Solar Cells

Femtosecond Pump–Probe Spectroscopy for Organic Photovoltaic Devices

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