Lead halide perovskites: Crystal-liquid duality, phonon glass electron crystals, and large polaron formation

Miyata, Kiyoshi; Atallah, Timothy; Zhu, Xiaoyang

doi:10.1126/sciadv.1701469

Cited by 378 publications

(460 citation statements)

References 138 publications

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“…Furthermore, MAPbI 3 exhibits flexible conductivity from good p-type to intrinsic and to good n-type depending on the chemical potentials (i.e., growth conditions), as shown in Figure 4c. [52,53] Adv. [43] The superior defect tolerance properties of Pb halide perovskites were confirmed by other groups.…”

Section: Excellent Defect Tolerancementioning

confidence: 99%

From Lead Halide Perovskites to Lead‐Free Metal Halide Perovskites and Perovskite Derivatives

2019

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serious challenges due to the inclusion of toxic Pb and instability against moisture, heat, and irradiation. In recent years, significant efforts have been paid to develop Pb-free halide perovskite and perovskite derivative absorber materials. However, so far, solar cells based on these materials show significantly inferior performances as compared to their Pb halide perovskite counterparts. Herein, we provide reviews on the fundamental understandings of the photovoltaic properties from Pb halide perovskites to Pb-free metal halide perovskites and perovskite derivatives as well as the experimental results reported in the literature. The results suggest that replacing Pb by nontoxic elements may degrade the superior photovoltaic properties seen in Pb halide perovskites, explaining the fact that all reported solar cells based on Pb-free perovskites or perovskite derivatives show performances significantly lower than Pb halide perovskite solar cells. Overview: Approaches and Consequences of Pb ReplacementWe first provide an overview of the approaches and consequences of Pb replacement reported in the literature, as shown in Figure 1. In general, there are two categories for Pb replacement: using either homovalent elements such as Sn and Ge or heterovalent elements such as Bi and Sb. The heterovalent replacement category can be divided into two subcategories based on the ways to maintain the charge neutrality: ion-splitting and ordered vacancy. The ion-splitting subcategory can be further divided into mixed anion compounds with the formula of AB(Ch,X) 3 , where Ch represents a chalcogen element, and X represents a halogen element, and mixed cation compounds with a formula of A 2 B(I)B(III)X 6 , which are commonly called double perovskites. The ordered vacancy subcategory can also be divided into the B(III) compounds with a formula of A 3 ◻B(III)X 9 and the B(IV) compounds with a formula of A 2 ◻ B(IV)X 6 (the sign of ◻ indicates vacancy). Figure 1 also summarizes the photovoltaic properties and the stabilities of each group of materials, which provides a clear overview of the consequences of Pb replacement. While the homovalent replacement by Sn or Ge leads to instability, the heterovalent Pb replacement leads to degraded electronic properties mainly due to the reduction on electronic dimensionality. As a result, all the reported Pb-free perovskite and perovskite derivative solar Despite the exciting progress on power conversion efficiencies, the commercialization of the emerging lead (Pb) halide perovskite solar cell technology still faces significant challenges, one of which is the inclusion of toxic Pb. Searching for Pb-free perovskite solar cell absorbers is currently an attractive research direction. The approaches used for and the consequences of Pb replacement are reviewed herein. Reviews on the theoretical understanding of the electronic, optical, and defect properties of Pb and Pb-free halide perovskites and perovskite derivatives are provided, as well as the experimental results available in the literature....

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Section: Excellent Defect Tolerancementioning

confidence: 99%

From Lead Halide Perovskites to Lead‐Free Metal Halide Perovskites and Perovskite Derivatives

2019

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“…[69] Thus, the actual initial HC temperature should be ≈580 K. The scattering of charge carriers with LO-phonons, charge defects, and even with one another can be reduced by the dynamic screening in polar semiconductors. [10,70] They suggested that the large polaron formation rate competes favorably with the initial LO-phonon cooling time to greatly slow down the HC cooling in MAPbBr 3 . [69,[72][73][74] Zhu et al proposed that the dynamical screening from the reorientational motions of the dipolar molecular cations and the large polaron formation give rise to the long-lived HCs in organic-inorganic hybrid perovskites.…”

Section: Large Polaron Formation At Low Carrier Densitymentioning

confidence: 99%

“…Notably, the large energy blueshift and highenergy tail are also present in steady-state PL spectra of FASnI 3 film under high pump-fluence continuous-wave (CW) excitation ( Figure 6d). [70] Copyright 2016, American Association for the Advancement of Science. Such strong emission from HCs under CW operation is an important development toward realizing HCSCs.…”

Section: Band-filling At High Carrier Densitymentioning

confidence: 99%

Slow Hot‐Carrier Cooling in Halide Perovskites: Prospects for Hot‐Carrier Solar Cells

et al. 2019

Advanced Materials

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rapidly (within hundreds of femtoseconds), making HCs extraction extremely challenging. A reduced HC cooling rate in solar absorbers is therefore a key material criterion for realizing HCSC.Halide perovskites possess novel slow HC cooling properties favorable for development as HCSC. Since the first reports of slow HC cooling (≈0.4 ps) in MAPbI 3 polycrystalline thin films, [7,8] there have been growing interests about this novel phenomenon. Li et al. reported a drastic slowdown of HC cooling by a further two orders in MAPbBr 3 colloidal nanocrystals (≈30 ps) at high pump fluence and demonstrated efficient (≈83%) extraction of HCs with an energy-selective organic layer. [9] Long HC transport lengths (≈600 nm) in MAPbI 3 thin films were visualized by Huang et al. [10] These exciting findings forebode the potential of perovskite HCSCs that could dramatically boost perovskite solar cell efficiencies beyond their SQ limits. Presently, the origins and mechanisms of slow HC cooling in halide perovskites remain fragmented and confusing with disparate models being proposed. A clear understanding of the intrinsic photophysics of HC cooling is essential for further technological developments.In this review, we examine the milestones and advancements of slow HC cooling in halide perovskites and distill their photophysical mechanisms. We begin with a brief introduction of the operation principles of HCSCs and carrier relaxation processes, followed by highlighting the seminal experimental and theoretical works on slow HC cooling in halide perovskites, before explicating their origins and mechanisms. A developmental toolbox for engineering slow HC cooling in halide perovskites and developing new perovskite materials with slower HC cooling will also be discussed. Lastly, we highlight the challenges and opportunities for perovskite HCSCs. How Hot Carriers Can Be Used?We begin with a quick overview of the several concepts for highefficiency solar cells. Figure 1a illustrates the energy band diagram of a typical single junction solar cell with its major energy loss processes following light illumination. [11,12] In all solar cells, photons possessing energies greater than the semiconductor bandgap can create free carriers or excitons with excess energies above the bandgap. These carriers or excitons with a temperature higher than the lattice temperature are termed "hot Rapid hot-carrier cooling is a major loss channel in solar cells. Thermodynamic calculations reveal a 66% solar conversion efficiency for single junction cells (under 1 sun illumination) if these hot carriers are harvested before cooling to the lattice temperature. A reduced hot-carrier cooling rate for efficient extraction is a key enabler to this disruptive technology. Recently, halide perovskites emerge as promising candidates with favorable hot-carrier properties: slow hot-carrier cooling lifetimes several orders of magnitude longer than conventional solar cell absorbers, longrange hot-carrier transport (up to ≈600 nm), and highly efficient hot-carrier extractio...

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“…We can estimate the crystal size from Debye-Scherrer equation, given by D size = Kλ/B size cosθ, where D size is Scherrer crystallite size, K is a unit cell geometrydependent constant, λ is the X-ray wavelength (λ = 1.5418 Å), B size is the peak width broadening due to the size effect, and θ is the Bragg angle. [44] In terms of lattices, Mn doping will enable the lattice contraction to slightly increase the bandgap, thus generating a more blue-shifted PL peak. Importantly, different from other films, QNC film with co-addition of FPEAI and Mn 2+ shows (100) plane at 14.26° instead of 14.23° ( Figure S16, Supporting Information), implying the crystal lattice is contracted due to Mn 2+ doping.…”

Section: Resultsmentioning

confidence: 99%

Rational Core–Shell Design of Open Air Low Temperature In Situ Processable CsPbI₃ Quasi‐Nanocrystals for Stabilized p‐i‐n Solar Cells

Piao

Byeon

et al. 2019

Advanced Energy Materials

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As a promising alternative, inorganic perovskite nanocrystals allow reinforced stability of photovoltaic device. Unfortunately, directly assembling these nanocrystals into film is uncontrollable. Instead, in situ assembling technology under low temperature in open air is attractive but limited due to the tendency of nonperovskite transition. The adverse shell ligands and unstable core lattices are known as the fundamental problems. In order to address this issue, here proposed is a rational core–shell design: 1) with respect to ligands, a new one, 4‐fluorophenethylammonium iodide, is used to enhance bonding force and charge coupling between ligands and nanocrystals; 2) with respect to lattices, a novel compound H2PbI4 is employed to assist divalent ion (Mn2+) doping into perovskite lattices. By low temperature in situ processing CsPbI3 quasi‐nanocrystal film, the highest power conversion efficiency of 13.4% for p‐i‐n solar cells is achieved, which retains 92% after 500 h in ambient air. The current study underlines the significance of rational hierarchical design of inorganic perovskite nanocrystals, especially for low temperature in situ processable electronic devices.

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Lead halide perovskites: Crystal-liquid duality, phonon glass electron crystals, and large polaron formation

Abstract: Efficient dynamic screening is key to the success of lead halide perovskites in solar cells and light emitting devices.

Cited by 378 publications

References 138 publications

From Lead Halide Perovskites to Lead‐Free Metal Halide Perovskites and Perovskite Derivatives

From Lead Halide Perovskites to Lead‐Free Metal Halide Perovskites and Perovskite Derivatives

Slow Hot‐Carrier Cooling in Halide Perovskites: Prospects for Hot‐Carrier Solar Cells

Rational Core–Shell Design of Open Air Low Temperature In Situ Processable CsPbI₃ Quasi‐Nanocrystals for Stabilized p‐i‐n Solar Cells

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Lead halide perovskites: Crystal-liquid duality, phonon glass electron crystals, and large polaron formation

Abstract: Efficient dynamic screening is key to the success of lead halide perovskites in solar cells and light emitting devices.

Cited by 378 publications

References 138 publications

From Lead Halide Perovskites to Lead‐Free Metal Halide Perovskites and Perovskite Derivatives

From Lead Halide Perovskites to Lead‐Free Metal Halide Perovskites and Perovskite Derivatives

Slow Hot‐Carrier Cooling in Halide Perovskites: Prospects for Hot‐Carrier Solar Cells

Rational Core–Shell Design of Open Air Low Temperature In Situ Processable CsPbI3 Quasi‐Nanocrystals for Stabilized p‐i‐n Solar Cells

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Rational Core–Shell Design of Open Air Low Temperature In Situ Processable CsPbI₃ Quasi‐Nanocrystals for Stabilized p‐i‐n Solar Cells