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Elucidating the reaction pathways in the synthesis of organolead trihalide perovskite for high-performance solar cells.

Wang B, Young Wong K, Xiao X, Chen T - Sci Rep (2015)

Bottom Line: Our study shows that gaseous products thermodynamically favour the reaction, while the activation energy and "collision" probability synergistically determine the reaction rate.These understandings enable us to finely tune the crystal size for high-quality perovskite film, leading to a record fill factor among similar device structures in the literature.This investigation provides a general strategy to explore the mechanism of perovskite synthesis and benefits the fabrication of high-efficiency perovskite photoactive layer.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, The Chinese University of Hong Kong, Shatin, N. T., Hong Kong, China.

ABSTRACT
The past two years have witnessed unprecedentedly rapid development of organic-inorganic halide perovskite-based solar cells. The solution-processability and high efficiency make this technology extraordinarily attractive. The intensive investigations have accumulated rich experiences in the perovskite fabrication; while the mechanism of the chemical synthesis still remains unresolved. Here, we set up the chemical equation of the synthesis and elucidate the reactions from both thermodynamic and kinetic perspectives. Our study shows that gaseous products thermodynamically favour the reaction, while the activation energy and "collision" probability synergistically determine the reaction rate. These understandings enable us to finely tune the crystal size for high-quality perovskite film, leading to a record fill factor among similar device structures in the literature. This investigation provides a general strategy to explore the mechanism of perovskite synthesis and benefits the fabrication of high-efficiency perovskite photoactive layer.

No MeSH data available.


Thermogravimetric analysis on the PbCl2 + 3CH3NH3I reaction system.a, The weight loss of the reaction precursors consists of PbCl2, CH3NH3I and DMF at 80 oC to evaporate the solvent, and 80–180 oC to initiate the reaction. b, Reaction rate–time plot of the PbCl2 + 3CH3NH3I reaction system at 150 oC. c, lnk–1/T plot of the reaction. d, The weight loss of the PbI2 + CH3NH3I system at 60 oC and 60–110 oC. e, Reaction rate–time plot of the reaction towards CH3NH3PbI3. f, lnk–1/T plot of the PbI2 + CH3NH3I system.
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f3: Thermogravimetric analysis on the PbCl2 + 3CH3NH3I reaction system.a, The weight loss of the reaction precursors consists of PbCl2, CH3NH3I and DMF at 80 oC to evaporate the solvent, and 80–180 oC to initiate the reaction. b, Reaction rate–time plot of the PbCl2 + 3CH3NH3I reaction system at 150 oC. c, lnk–1/T plot of the reaction. d, The weight loss of the PbI2 + CH3NH3I system at 60 oC and 60–110 oC. e, Reaction rate–time plot of the reaction towards CH3NH3PbI3. f, lnk–1/T plot of the PbI2 + CH3NH3I system.

Mentions: In the thermogravimetric analysis (TGA) of reaction (9), the precursor solution was pre-dried at 80 oC for 2.5 hours to evaporate the DMF out of the mixture (Fig. 3a and Supplementary Fig. 3). Subsequently, the precursor powder was heated to initiate the reaction. It should be noted that the amount of the reaction precursor for TGA measurement (milligram scale) is significantly greater than that for device fabrication, the latter of which is usually a thin layer of film of several hundred nanometers thick. Therefore, the required heating temperature for the reaction in the TGA measurement must be higher than the latter due to the temperature gradient inside the precursors. We thus recorded the reaction rate in the temperature ranging from 80 to 180 oC. We found that toward the end, the weight loss fraction reaches 15.2% (Fig. 3a), which is a little smaller than the theoretical weight loss fraction, possibly because the reaction has occurred during the pre-drying process. However, this would not influence the rationality of our method in that we quantify the gas release associated reaction rate at a specific temperature and duration.


Elucidating the reaction pathways in the synthesis of organolead trihalide perovskite for high-performance solar cells.

Wang B, Young Wong K, Xiao X, Chen T - Sci Rep (2015)

Thermogravimetric analysis on the PbCl2 + 3CH3NH3I reaction system.a, The weight loss of the reaction precursors consists of PbCl2, CH3NH3I and DMF at 80 oC to evaporate the solvent, and 80–180 oC to initiate the reaction. b, Reaction rate–time plot of the PbCl2 + 3CH3NH3I reaction system at 150 oC. c, lnk–1/T plot of the reaction. d, The weight loss of the PbI2 + CH3NH3I system at 60 oC and 60–110 oC. e, Reaction rate–time plot of the reaction towards CH3NH3PbI3. f, lnk–1/T plot of the PbI2 + CH3NH3I system.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4447066&req=5

f3: Thermogravimetric analysis on the PbCl2 + 3CH3NH3I reaction system.a, The weight loss of the reaction precursors consists of PbCl2, CH3NH3I and DMF at 80 oC to evaporate the solvent, and 80–180 oC to initiate the reaction. b, Reaction rate–time plot of the PbCl2 + 3CH3NH3I reaction system at 150 oC. c, lnk–1/T plot of the reaction. d, The weight loss of the PbI2 + CH3NH3I system at 60 oC and 60–110 oC. e, Reaction rate–time plot of the reaction towards CH3NH3PbI3. f, lnk–1/T plot of the PbI2 + CH3NH3I system.
Mentions: In the thermogravimetric analysis (TGA) of reaction (9), the precursor solution was pre-dried at 80 oC for 2.5 hours to evaporate the DMF out of the mixture (Fig. 3a and Supplementary Fig. 3). Subsequently, the precursor powder was heated to initiate the reaction. It should be noted that the amount of the reaction precursor for TGA measurement (milligram scale) is significantly greater than that for device fabrication, the latter of which is usually a thin layer of film of several hundred nanometers thick. Therefore, the required heating temperature for the reaction in the TGA measurement must be higher than the latter due to the temperature gradient inside the precursors. We thus recorded the reaction rate in the temperature ranging from 80 to 180 oC. We found that toward the end, the weight loss fraction reaches 15.2% (Fig. 3a), which is a little smaller than the theoretical weight loss fraction, possibly because the reaction has occurred during the pre-drying process. However, this would not influence the rationality of our method in that we quantify the gas release associated reaction rate at a specific temperature and duration.

Bottom Line: Our study shows that gaseous products thermodynamically favour the reaction, while the activation energy and "collision" probability synergistically determine the reaction rate.These understandings enable us to finely tune the crystal size for high-quality perovskite film, leading to a record fill factor among similar device structures in the literature.This investigation provides a general strategy to explore the mechanism of perovskite synthesis and benefits the fabrication of high-efficiency perovskite photoactive layer.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, The Chinese University of Hong Kong, Shatin, N. T., Hong Kong, China.

ABSTRACT
The past two years have witnessed unprecedentedly rapid development of organic-inorganic halide perovskite-based solar cells. The solution-processability and high efficiency make this technology extraordinarily attractive. The intensive investigations have accumulated rich experiences in the perovskite fabrication; while the mechanism of the chemical synthesis still remains unresolved. Here, we set up the chemical equation of the synthesis and elucidate the reactions from both thermodynamic and kinetic perspectives. Our study shows that gaseous products thermodynamically favour the reaction, while the activation energy and "collision" probability synergistically determine the reaction rate. These understandings enable us to finely tune the crystal size for high-quality perovskite film, leading to a record fill factor among similar device structures in the literature. This investigation provides a general strategy to explore the mechanism of perovskite synthesis and benefits the fabrication of high-efficiency perovskite photoactive layer.

No MeSH data available.