Direct calorimetric verification of thermodynamic instability of lead halide hybrid perovskites

Nagabhushana, G. P.; Shivaramaiah, Radha; Navrotsky, Alexandra

doi:10.1073/pnas.1607850113

Cited by 348 publications

(294 citation statements)

References 35 publications

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“…[266] Despite the differences between these studies, all report that MAPbI 3 was found to be the least stable, while MAPbCl 3 is the most stable. Partially substituting the iodide with bromide or chloride would, therefore, be expected to improve the thermodynamic stability of the perovskite compared to the pure iodide material, while maintaining the good photovoltaic performance.…”

Section: Mixed-halide Mixed-cation Perovskitesmentioning

confidence: 89%

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

Petrus

Schlipf

Cheng

et al. 2017

Advanced Energy Materials

304

201

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following statement: These materials can be processed from solution and yet exhibit optoelectronic materials properties described in classic solid-state physics textbooks. This unprecedented combination has led to photovoltaic devices that can be processed at room temperature and achieve performance levels similar to industry giant polycrystalline silicon, from a starting point of 3.8% in 2009. [1][2][3][4] The first light-emitting electrochemical cells [5] and diodes [6][7][8] have also been introduced recently, leading to tunable light emission spectra and internal quantum efficiencies exceeding 15%.The road towards these achievements has been marked by a constant improvement of perovskite deposition techniques fueled by our increasing understanding of the crystallization processes. The choice of deposition technique, either from solution or vapor, and the composition and order in which precursor species are applied has a great influence on the crystallization kinetics. Here, one can distinguish one-step methods where the perovskite is formed from a precursor mixture dissolved in a common solution, and two-step methods where the inorganic compound is deposited first and transformed to the perovskite phase later by addition of the organic constituents. [9][10][11] Furthermore, many parameters during processing can have an effect on the crystallization mechanism and consequently on film morphology, such as the choice of solvents, concentrations and processing additives that are often not incorporated into the final product. [11][12][13] We discuss this aspect in Section 2, where we focus our attention on the most commonly employed solution-based techniques. Additionally, as for any new technology trying to displace an incumbent technology, higher efficiencies, lower costs, reproducibility, stability, and sustainability are paramount. In particular, reproducibility has been a major challenge in perovskite solar cells from the beginning: small variations in morphology, like crystal size, film roughness, and pinholes can have detrimental effects on photovoltaic performance. [14] On the other hand, current-voltage measurements often showed a hysteresis that is rarely seen in other photovoltaic technologies. [15] These topics are highlighted in Sections 3 and 4. Finally, in Section 5 we discuss the framework for market introduction, such as cost reduction by choosing low-cost charge transport layers, or how the lifetime of perovskite absorbers can be extended by the choice of materials composition.Hybrid metal halide perovskites have become one of the hottest topics in optoelectronic materials research in recent years. Not only have they surpassed everyone's expectations and achieved similar performance as tried and true polycrystalline silicon photovoltaic devices, but they are also finding applications in a variety of different fields, including lighting. The main advantages of hybrid metal halide perovskites are simple processability, compatible with large-scale solution processing such as roll-to-roll printing, a...

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Section: Mixed-halide Mixed-cation Perovskitesmentioning

confidence: 89%

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

Petrus

Schlipf

Cheng

et al. 2017

Advanced Energy Materials

304

201

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“…Using direct calorimetric techniques, Navrotsky et al 37 have shown MAPI to be thermodynamically unstable with respect to decomposition to PbI 2 and MAI. Here, the same intrinsic decomposition reaction was investigated involving the formation of PbI 2 and organic iodides as well as decomposition to the d-phase:…”

Section: -36mentioning

confidence: 99%

Understanding the stability of mixed A-cation lead iodide perovskites

et al. 2017

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The routes and kinetics of the degradation of thin films of methylammonium (MA)/formamidinium (FA) lead iodide perovskites (MA 1Àx FA x PbI 3 , 0 # x # 1) under dry atmospheric conditions have been investigated. MA-rich phases decompose to the precursor iodide salts and PbI 2 , while FA-rich phases convert mainly to the yellow hexagonal phase. The reactivity is strongly inhibited for mixed cation phases of MA 1Àx FA x PbI 3 , for x ¼ 0.4 to 0.6, where the decomposition routes available to end member phases become less favourable. It is shown that for pristine films with x ¼ 0.6, PbI 2 formation can be completely suppressed for up to 10 days. Kinetic analysis reveals that the rate of PbI 2 formation decays exponentially with increasing FA content until x ¼ 0.7, beyond which the FA containing perovskite transforms rapidly to the hexagonal phase. Ab initio simulations of the decomposition reaction energies fully support the increased kinetic stability found experimentally for the mixed A-cation perovskites.Hybrid lead halide perovskites have recently risen to prominence as highly versatile materials for optoelectronic technologies, particularly high efficiency, solution processed solar cells.1-4 They display near optimal band gap for solar light absorption, high absorption coefficients, steep absorption onsets and signicant charge carrier lifetimes (and thus diffusion lengths).2,5 These properties, combined with the processability of these materials, 6,7 have resulted in solar cell device efficiencies rising rapidly to over 22%.8 However, the commercial applicability of these materials is hampered by their relative lack of stability compared to established inorganic and organic semiconductors.9-11 By chemical site-substitution at any of the A, B or X sites of the ABX 3 perovskite structure, it has been found that it is possible to tune the properties and, most pertinently, the stability of the resultant material. 12-14The archetypal hybrid perovskite methylammonium (MA) lead iodide (CH 3 NH 3 PbI 3 ), MAPI, crystallises in the tetragonal space group I4/mcm at room temperature.15 Formamidinium (FA) lead iodide (CH(NH 2 ) 2 PbI 3 ), FAPI, by contrast preferentially crystallises in the yellow, 2H hexagonal perovskite type polymorph at room temperature, which can be driven to transform to the black cubic perovskite polymorph (required for photovoltaic applications) by heating above room temperature. 16-19Such varying phase behaviour can be accounted for by the different sizes and hydrogen bonding mechanisms of these dissimilar organic cations, MA and FA.Both MA and FA cations display directional hydrogen bonding, a factor of increasing importance in controlling phase behaviour as the system temperature is reduced and also for dening the relative stability of the two polymorphs of FAPI. 20Stabilisation of mixed A site compounds relative to the end members of the series can be rationalised using geometrical arguments in which the perovskite tolerance factor is tuned using differently sized cations, as well as an entrop...

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“…The lattice energies of CH 3 20 . Lattice energies of the corresponding inorganic perovskites (CsPbI 3 , CsPbBr 3 and CsPbCl 3 ) are very similar to their organic counterparts.…”

Section: B Stability Analysis Of Hybrid Organic Halide Perovksitesmentioning

confidence: 99%

Ionization Energy as a Stability Criterion for Halide Perovskites

Zheng

Rubel

2017

J. Phys. Chem. C

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Instability of hybrid organic-inorganic halide perovskites hinders their development for photovoltaic applications. First-principle calculations are used for evaluation of a decomposition reaction enthalpy of hybrid halide perovskites, which is linked to experimentally observed degradation of device characteristics. However, simple criteria for predicting stability of halide perovskites are lacking since Goldschmidt's tolerance and octahedral geometrical factors do not fully capture formability of those perovskites. In this paper, we extend the Born-Haber cycle to partition the reaction enthalpy of various perovskite structures into lattice, ionization, and molecularization energy components. The analysis of various contributions to the reaction enthalpy points to an ionization energy of a molecule and a cage as an additional criterion for predicting chemical trends in stability of hybrid halide perovskites. Prospects of finding new perovskite structures with improved chemical stability aimed for photovoltaic applications are discussed.

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Direct calorimetric verification of thermodynamic instability of lead halide hybrid perovskites

Cited by 348 publications

References 35 publications

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

Understanding the stability of mixed A-cation lead iodide perovskites

Ionization Energy as a Stability Criterion for Halide Perovskites

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