scholarly journals Photovoltaic mixed-cation lead mixed-halide perovskites: links between crystallinity, photo-stability and electronic properties

2017 ◽  
Vol 10 (1) ◽  
pp. 361-369 ◽  
Author(s):  
Waqaas Rehman ◽  
David P. McMeekin ◽  
Jay B. Patel ◽  
Rebecca L. Milot ◽  
Michael B. Johnston ◽  
...  
Keyword(s):  
Charge Carrier ◽  
Band Gap ◽  
Electronic Properties ◽  
Photovoltaic Cells ◽  
Lead Iodide ◽  
Tunable Materials ◽  
Mixed Cation ◽  
Halide Perovskites ◽  
Compositional Effects ◽  
Photo Stability

We establish compositional effects on stability, crystallinity, charge-carrier life times and mobilities in mixed-cation lead iodide-bromide perovskites as band gap tunable materials for multi-junction photovoltaic cells.

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>

scholarly journals Structural, electronic, and optical properties of cubic formamidinium lead iodide perovskite: a first-principles investigation

RSC Advances ◽  
2020 ◽  
Vol 10 (54) ◽  
pp. 32364-32369
Author(s):  
Sanjun Wang ◽  
Wen-bo Xiao ◽  
Fei Wang
Keyword(s):  
Optical Properties ◽  
Charge Carrier ◽  
Electronic Properties ◽  
First Principles ◽  
Carrier Mobility ◽  
Charge Carrier Mobility ◽  
Detailed Structure ◽  
Lead Iodide ◽  
Theoretical Methods ◽  
Band Splitting

Different theoretical methods, including SOC effects, were used to study the detailed structure, electronic properties, charge-carrier mobility, and SOC-induced Rashba k-dependent band splitting in FAPbI3.

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>

Structural properties of GaAs/InGaAs/GaAs (001) and InGaAs/GaAs (001) heterostructures and correlation with electronic properties

1990 ◽  
Vol 48 (4) ◽  
pp. 602-603
Author(s):  
J.M. Bonar ◽  
R. Hull ◽  
R. Malik ◽  
R. Ryan ◽  
J.F. Walker
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Gaas Substrate ◽  
Critical Thickness ◽  
Lattice Mismatch ◽  
Band Offset ◽  
Misfit Dislocations ◽  
Gaas Substrates ◽  
Gaas Structure ◽  
Low X

In this study we have examined a series of strained heteropeitaxial GaAs/InGaAs/GaAs and InGaAs/GaAs structures, both on (001) GaAs substrates. These heterostructures are potentially very interesting from a device standpoint because of improved band gap properties (InAs has a much smaller band gap than GaAs so there is a large band offset at the InGaAs/GaAs interface), and because of the much higher mobility of InAs. However, there is a 7.2% lattice mismatch between InAs and GaAs, so an InxGa1-xAs layer in a GaAs structure with even relatively low x will have a large amount of strain, and misfit dislocations are expected to form above some critical thickness. We attempt here to correlate the effect of misfit dislocations on the electronic properties of this material.The samples we examined consisted of 200Å InxGa1-xAs layered in a hetero-junction bipolar transistor (HBT) structure (InxGa1-xAs on top of a (001) GaAs buffer, followed by more GaAs, then a layer of AlGaAs and a GaAs cap), and a series consisting of a 200Å layer of InxGa1-xAs on a (001) GaAs substrate.

Lead-Free Metal Halide Perovskite Nanocrystals for Photocatalysis in Water

2019 ◽  
Author(s):  
Subhajit Bhattacharjee ◽  
Sonu Pratap Chaudhary ◽  
Sayan Bhattacharyya
Keyword(s):  
Charge Carrier ◽  
Wide Spectrum ◽  
Real Life ◽  
Metal Halide ◽  
Lead Free ◽  
Water Medium ◽  
Type I ◽  
Type Ii ◽  
Perovskite Layer ◽  
Halide Perovskites

<p>Metal halide perovskites with high absorption coefficient, direct generation of free charge carriers, excellent ambipolar charge carrier transport properties, point-defect tolerance, compositional versatility and solution processability are potentially transforming the photovoltaics and optoelectronics industries. However their limited ambient stability, particularly those of iodide perovskites, obscures their use as photocatalysts especially in aqueous medium. In an unprecedented approach we have exploited the photo-absorption property of the less toxic lead-free Cs<sub>3</sub>Bi<sub>2</sub>X<sub>9 </sub>(X = Br, I) nanocrystals (NCs) to catalyse the degradation of water pollutant organic dye, methylene blue (MB) in presence of visible light at room temperature. After providing a proof-of-concept with bromide perovskites in isopropanol, the perovskites are employed as photocatalysts in water medium by designing perovskite/Ag<sub>2</sub>S and perovskite/TiO<sub>2 </sub>composite systems, with Type I (or quasi Type II) and Type II alignments, respectively. Ag<sub>2</sub>S and TiO<sub>2</sub> coatings decelerate penetration of water into the perovskite layer while facilitating charge carrier extraction. With a minimal NC loading, Cs<sub>3</sub>Bi<sub>2</sub>I<sub>9</sub>/Ag<sub>2</sub>S degrades ~90% MB within an hour. Our approach has the potential to unravel the photocatalytic properties of metal halide perovskites for a wide spectrum of real-life applications. </p>

Limits of Charge Carrier Transport in Halide Perovskites Revealed by Optical-Pump Terahertz-Probe Spectroscopy

2019 ◽  
Author(s):  
Hannes Hempel ◽  
Andrei Petsiu ◽  
Martin Stolterfoht ◽  
Pascal Becker ◽  
Dieter Neher ◽  
...  
Keyword(s):  
Charge Carrier ◽  
Carrier Transport ◽  
Charge Carrier Transport ◽  
Optical Pump ◽  
Halide Perovskites ◽  
Probe Spectroscopy

scholarly journals Reversible oxygen-induced p-doping of mixed-cation halide perovskites

APL Materials ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 081104
Author(s):  
Dongguen Shin ◽  
Fengshuo Zu ◽  
Norbert Koch
Keyword(s):  
Mixed Cation ◽  
Halide Perovskites
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