scholarly journals Unified theory for light-induced halide segregation in mixed halide perovskites

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Zehua Chen ◽  
Geert Brocks ◽  
Shuxia Tao ◽  
Peter A. Bobbert
Keyword(s):  
Band Gap ◽  
Parent Phase ◽  
Thermodynamic Theory ◽  
Partial Replacement ◽  
Organic Cations ◽  
Temperature Phase ◽  
Unified Theory ◽  
Rich Phase ◽  
Energy Lowering ◽  
Halide Perovskites

AbstractMixed halide perovskites that are thermodynamically stable in the dark demix under illumination. This is problematic for their application in solar cells. We present a unified thermodynamic theory for this light-induced halide segregation that is based on a free energy lowering of photocarriers funnelling to a nucleated phase with different halide composition and lower band gap than the parent phase. We apply the theory to a sequence of mixed iodine-bromine perovskites. The spinodals separating metastable and unstable regions in the composition-temperature phase diagrams only slightly change under illumination, while light-induced binodals separating stable and metastable regions appear signalling the nucleation of a low-band gap iodine-rich phase. We find that the threshold photocarrier density for halide segregation is governed by the band gap difference of the parent and iodine-rich phase. Partial replacement of organic cations by cesium reduces this difference and therefore has a stabilizing effect.

scholarly journals Unified theory for light-induced halide segregation in mixed halide perovskites

2020 ◽  
Author(s):  
Zehua Chen ◽  
Geert Brocks ◽  
Shuxia Tao ◽  
Peter Bobbert
Keyword(s):  
Band Gap ◽  
Parent Phase ◽  
Thermodynamic Theory ◽  
Partial Replacement ◽  
Organic Cations ◽  
Temperature Phase ◽  
Unified Theory ◽  
Rich Phase ◽  
Energy Lowering ◽  
Halide Perovskites

Abstract Mixed halide perovskites that are thermodynamically stable in the dark demix under illumination. This is problematic for their application in solar cells. We present a unified thermodynamic theory for this light-induced halide segregation that is based on a free energy lowering of photocarriers funnelling to a nucleated phase with different halide composition and lower band gap than the parent phase. We apply the theory to a sequence of mixed iodine-bromine perovskites. The spinodals separating metastable and unstable regions in the composition-temperature phase diagrams only slightly change under illumination, while light-induced binodals separating stable and metastable regions appear signalling the nucleation of a low-band gap iodine-rich phase. We find that the threshold photocarrier density for halide segregation is governed by the band gap difference of the parent and iodine-rich phase. Partial replacement of organic cations by cesium reduces this difference and therefore has a stabilizing effect.

Bulky Organic Cations Engineered Lead-halide Perovskites: A Review on Dimensionality and Optoelectronic Applications

2021 ◽  
pp. 100759
Author(s):  
Hock Beng Lee ◽  
Neetesh Kumar ◽  
Barkha Tyagi ◽  
Siwei He ◽  
Rishabh Sahani ◽  
...  
Keyword(s):  
Organic Cations ◽  
Halide Perovskites ◽  
Optoelectronic Applications ◽  
Lead Halide

Effects of organic cations on the defect physics of tin halide perovskites

2017 ◽  
Vol 5 (29) ◽  
pp. 15124-15129 ◽  
Author(s):  
Tingting Shi ◽  
Hai-Shan Zhang ◽  
Weiwei Meng ◽  
Qiang Teng ◽  
Meiyue Liu ◽  
...  
Keyword(s):  
Organic Cations ◽  
Schematic Diagram ◽  
Bond Lengths ◽  
Halide Perovskites

The schematic diagram of different Sn-5s and I-5p antibonding strengths of FASnI3 and MASnI3 due to various bond lengths of Sn–I.

A study on the effects of mixed organic cations on the structure and properties in lead halide perovskites

2020 ◽  
Vol 22 (5) ◽  
pp. 3105-3111 ◽  
Author(s):  
Chao Wu ◽  
Daoyou Guo ◽  
Peigang Li ◽  
Shunli Wang ◽  
Aiping Liu ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Single Crystals ◽  
Electrical Transport ◽  
Organic Cation ◽  
Organic Cations ◽  
Structure And Properties ◽  
Electrical Transport Properties ◽  
Halide Perovskites ◽  
A Site ◽  
Lead Halide

Four types of organic cation-mixed single crystals were successfully synthesized by partially substituting A site cations to investigate the effect of organic cations on structure, optical features, thermal stability, and electrical transport properties.

35Cl NQR Studies of Hexachlorometallates(IV) with Organic Cations, A2 [MCl6] and A'[MCl6], M=Sn, Te, Pb and A+, A'2+ = Organic Cation

1990 ◽  
Vol 45 (3-4) ◽  
pp. 293-302 ◽  
Author(s):  
Dirk Borchers ◽  
Alarich Weiss
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Low Temperature ◽  
Resonance Line ◽  
Organic Cation ◽  
Phase Changes ◽  
Organic Cations ◽  
Temperature Phase ◽  
35Cl Nqr ◽  
Low Temperature Phase

Abstract35Cl NQR spectra of eleven hexachlorometallates (IV) A1 [MCl6] and A'[MCl6], M = Sn, Te, Pb, and A+ =ethylammonium, 4-picolinium, anilinium, triethylammonium, chinoxalinium, and piperi-dinium ions, and A'2+ = 1.3-propylenediammonium ion, have been observed as a function of tem-perature. The ethylammonium hexachlorometallates(IV) (C2H5 NH3)2 [MCl6], M = Sn, Te, show a phase transition at 128.8 K and 204 K, respectively. Both compounds yield a single resonance line in their high temperature phases. In case of the stannate this single 35Cl resonance line splits up into two lines at Tc = 128.8 K, whereas for the tellurate no 35Cl NQR signals could be found in the low temperature phase. A phase transition was also found for the 1.3-propylenediammonium hexa-chlorostannate(IV) at 287 K where the six line NQR spectrum of the low temperature phase changes into a four line spectrum. In contrast, the corresponding plumbate shows no transition. All other compounds studied contain distorted [MCl6]2- octahedra, and therefore they yield more than one 35Cl resonance line. The complexes have been investigated in the temperature range temperature where the lines fade out. In case of the hexachlorostannates(IV) with the ethylammonium, the 1.3-propylenediammonium and the triethylammonium ions, the crystal structures of the compounds are known and compared with the results of the 35Cl NQR spectroscopy.

scholarly journals Chemi-Structural Stabilization of Formamidinium Lead Iodide Perovskite by Using Embedded Quantum Dots for High-Performance Solar Cells

2019 ◽  
Author(s):  
Sofia Masi ◽  
Carlos Echeverría-Arrondo ◽  
Salim K.P. Muhammed ◽  
Thi Tuyen Ngo ◽  
Perla F. Méndez ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Solar Cells ◽  
Band Gap ◽  
High Efficiency ◽  
Perovskite Phase ◽  
Perovskite Solar Cells ◽  
Relative Size ◽  
Lead Iodide ◽  
Structural Stabilization ◽  
Halide Perovskites

<b>The extraordinary low non-radiative recombination and band gap versatility of halide perovskites have led to considerable development in optoelectronic devices. However, this versatility is limited by the stability of the perovskite phase, related to the relative size of the different cations and anions. The most emblematic case is that of formamidinium lead iodine (FAPI) black phase, which has the lowest band gap among all 3D lead halide perovskites, but quickly transforms into the non-perovskite yellow phase at room temperature. Efforts to optimize perovskite solar cells have largely focused on the stabilization of FAPI based perovskite structures, often introducing alternative anions and cations. However, these approaches commonly result in a blue-shift of the band gap, which limits the maximum photo-conversion efficiency. Here, we report the use of PbS colloidal quantum dots (QDs) as stabilizing agent for the FAPI perovskite black phase. The surface chemistry of PbS plays a pivotal role, by developing strong bonds with the black phase but weak ones with the yellow phase. As a result, stable FAPI black phase can be formed at temperatures as low as 85°C in just 10 minutes, setting a record of concomitantly fast and low temperature formation for FAPI, with important consequences for industrialization. FAPI thin films obtained through this procedure preserve the original low band gap of 1.5 eV, reach a record open circuit potential (V<sub>oc</sub>) of 1.105 V -91% of the maximum theoretical V<sub>oc</sub>- and preserve high efficiency for more than 700 hours. These findings reveal the potential of strategies exploiting the chemi-structural properties of external additives to relax the tolerance factor and optimize the optoelectronic performance of perovskite materials.</b>

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