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Related Concept Videos

Alkyl Halides02:45

Alkyl Halides

20.2K
Structural Properties
Alkyl halides are halogen-substituted alkanes wherein one or more hydrogen atoms of an alkane is replaced by a halogen atom such as fluorine, chlorine, bromine, or iodine. The carbon atom in an alkyl halide is bonded to the halogen atom, which is sp3-hybridized and exhibits a tetrahedral shape.
Unlike alkyl halides, compounds in which a halogen atom is bonded to an sp2 -hybridized carbon atom of a carbon-carbon double bond (C=C) are called vinyl halides. Whereas aryl...
20.2K
Acid Halides to Esters: Alcoholysis01:12

Acid Halides to Esters: Alcoholysis

4.1K
Alcoholysis is a nucleophilic acyl substitution reaction in which an alcohol functions as a nucleophile. Acid halides react with alcohol to produce esters. The mechanism proceeds in three steps:
4.1K
Series R—L Circuit Transients01:22

Series R—L Circuit Transients

434
In a series resistor-inductor (R-L) circuit, closing the switch at the start of the time period simulates a three-phase short circuit, a fault condition where all three phases of an unloaded synchronous machine are short-circuited. When there is no fault impedance and no initial current, the initial voltage is determined by the phase angle of the source voltage.
Using Kirchhoff's Voltage Law (KVL) to analyze this circuit helps determine the total asymmetrical fault current, which consists...
434
Mass Spectrometry: Alkyl Halide Fragmentation01:22

Mass Spectrometry: Alkyl Halide Fragmentation

1.6K
Chlorine isotopes exist as 35Cl and 37Cl in a 3:1 ratio, while bromine isotopes exist as 79Br and 81Br in a 1:1 ratio. The mass spectrum of alkyl halides typically produces two distinct molecular ion peaks, the molecular ion peak, [M], and the molecular ion plus two, [M + 2] peak. The relative heights of these two peaks are proportional to the isotopic abundance ratios of the halide. For example, 2‐chloropropane and 1‐bromopropane display two peaks with relative peak heights in a 3:1 and...
1.6K
Acid Halides to Carboxylic Acids: Hydrolysis01:01

Acid Halides to Carboxylic Acids: Hydrolysis

3.6K
Hydrolysis of acid halides is a nucleophilic acyl substitution reaction in which acid halides react with water to give carboxylic acids. The reaction occurs readily and does not require acid or a base catalyst.
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic...
3.6K
Acid Halides to Amides: Aminolysis01:07

Acid Halides to Amides: Aminolysis

4.4K
Aminolysis is a nucleophilic acyl substitution reaction, where ammonia or amines act as nucleophiles to give the substitution product. Acid halides react with ammonia, primary amines, and secondary amines to yield primary, secondary, and tertiary amides, respectively.
In the first step of the aminolysis mechanism, the amine attacks the carbonyl carbon of the acyl chloride to form a tetrahedral intermediate. In the second step, the carbonyl group is re-formed with the elimination of a chloride...
4.4K

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Connecting the Dots: Discovery of the (M<b><sub>2</sub></b>Q<b><sub>3</sub></b>)<b><sub>2</sub></b>(AMQ<b><sub>2</sub></b>)<b><i><sub>n</sub></i></b> Homologous Series through Cs<b><sub>5</sub></b>Bi<b><sub>9</sub></b>S<b><sub>16</sub></b> (<i>n</i> = 5).

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Related Experiment Video

Updated: Feb 15, 2026

Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films
08:12

Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films

Published on: September 8, 2017

10.1K

Transient Sub-bandgap States in Halide Perovskite Thin Films.

S Nah1, B Spokoyny1, X Jiang

  • 1Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.

Nano Letters
|January 31, 2018
PubMed
Summary

Directly observed sub-bandgap states in metal halide perovskites using single-particle microscopy. These transient states improve solar cell efficiency by protecting carriers from defects.

Keywords:
Metal halide perovskitepolaron statesspatially resolved measurementstransient absorption microscopyultrafast spectroscopy

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Inkjet Printing All Inorganic Halide Perovskite Inks for Photovoltaic Applications
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Inkjet Printing All Inorganic Halide Perovskite Inks for Photovoltaic Applications

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Facile Synthesis of Colloidal Lead Halide Perovskite Nanoplatelets via Ligand-Assisted Reprecipitation
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Facile Synthesis of Colloidal Lead Halide Perovskite Nanoplatelets via Ligand-Assisted Reprecipitation

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Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films
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Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films

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Inkjet Printing All Inorganic Halide Perovskite Inks for Photovoltaic Applications
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Facile Synthesis of Colloidal Lead Halide Perovskite Nanoplatelets via Ligand-Assisted Reprecipitation
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Facile Synthesis of Colloidal Lead Halide Perovskite Nanoplatelets via Ligand-Assisted Reprecipitation

Published on: October 1, 2019

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Area of Science:

  • Materials Science
  • Solid-State Physics
  • Photovoltaics

Background:

  • Metal halide perovskites are promising for solar energy due to their unique properties.
  • The exact mechanism behind their high efficiency, particularly the role of stabilized states like polarons, remains unclear.
  • Previous studies lacked direct evidence for these low-energy states, often masked in ensemble measurements.

Purpose of the Study:

  • To directly identify and characterize sub-bandgap states in methylammonium lead iodide (MAPbI3) perovskites.
  • To investigate the role of these states in carrier dynamics and their contribution to device efficiency.
  • To understand why ensemble measurements fail to detect these crucial states.

Main Methods:

  • Single-particle transient absorption microscopy was employed on MAPbI3.
  • Carrier temperature-dependent studies were conducted.
  • Comparison between single-particle and ensemble measurement techniques.

Main Results:

  • Unambiguous identification of spectrally narrow sub-bandgap states at the single-particle level.
  • Demonstration that ensemble measurements average out these critical signals.
  • Evidence suggests hot carriers are funneled into transient, low-energy states, avoiding defects.

Conclusions:

  • The existence of short-lived, sub-bandgap states is confirmed in perovskites.
  • These states protect carriers from recombination centers, leading to high power conversion efficiencies.
  • Harnessing these transient states could be key for advancing heterogeneous optoelectronic materials.