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Polymer Solar Cells: Understanding S...

Chang, Lilian.

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Polymer Solar Cells: Understanding Solvent Interactions and Morphology, and Strategies for Efficiency Improvements.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Polymer Solar Cells: Understanding Solvent Interactions and Morphology, and Strategies for Efficiency Improvements./
Author:	Chang, Lilian.
Description:	157 p.
Notes:	Source: Dissertation Abstracts International, Volume: 74-10(E), Section: B.
Contained By:	Dissertation Abstracts International74-10B(E).
Subject:	Energy. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3565489
ISBN:	9781303152986

Polymer Solar Cells: Understanding Solvent Interactions and Morphology, and Strategies for Efficiency Improvements.
Chang, Lilian.

Polymer Solar Cells: Understanding Solvent Interactions and Morphology, and Strategies for Efficiency Improvements. - 157 p.

Source: Dissertation Abstracts International, Volume: 74-10(E), Section: B.

Thesis (Ph.D.)--University of California, Davis, 2013.

Organic solar cells have the potential to be unrivaled in terms of processing cost, speed, and simplicity. The simplest of such devices consists of a single bulk-heterojunction (BHJ) active layer, in which the electron donor (conjugated polymer) and electron acceptor (fullerene) are deposited from a common solvent. The performance of BHJ solar cells is strongly correlated with the nanoscale structure of the active layer. Various processing techniques have been explored to improve the nanoscale morphology of the BHJ layer, e.g. by varying the casting solvent, thermal annealing, solvent annealing, and solvent additives. An understanding of the role of residual solvent in the BHJ layer is imperative in order to develop strategies for morphology stabilization and preserve the longevity of the device. This work highlights the effect of residual solvents on acceptor, (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) diffusion and ultimately the stability of the morphology. We first show that solvent is retained within the BHJ film despite prolonged heat treatment, leading to extensive phase separation between poly(3-hexylthiophene) (P3HT) and PCBM. We then show that the addition of a small volume fraction of nitrobenzene to the casting solution inhibits the diffusion of PCBM in the film and improves the fill factor of the BHJ device without further tempering. Other commonly used additives for morphology improvement were also investigated, i.e. 1,8-diiodooctane and 1-chloronaphthalene. We show that the choice of solvent additives has direct implications on morphological evolution, i.e. P3HT:PCBM BHJ films processed with a small amount of 1,8-diiodooctane or 1-chloronaphthalene have more crystalline PCBM domains compared to crystalline P3HT domains, while the opposite is true for films cast with nitrobenzene additive and films cast purely from chlorobenzene. The BHJ film cross-links when annealed at 300&degC in the presence of 1,8-diiodooctane. Cross-linking is found to occur even in pristine P3HT and PCBM films annealed under similar conditions.

ISBN: 9781303152986Subjects--Topical Terms:

876794
Energy.

Polymer Solar Cells: Understanding Solvent Interactions and Morphology, and Strategies for Efficiency Improvements.
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020 $a 9781303152986
035 $a (MiAaPQ)AAI3565489
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040 $a MiAaPQ $c MiAaPQ
100 1 $a Chang, Lilian. $3 2094939
245 1 0 $a Polymer Solar Cells: Understanding Solvent Interactions and Morphology, and Strategies for Efficiency Improvements.
300 $a 157 p.
500 $a Source: Dissertation Abstracts International, Volume: 74-10(E), Section: B.
500 $a Adviser: Adam J. Moule.
502 $a Thesis (Ph.D.)--University of California, Davis, 2013.
520 $a Organic solar cells have the potential to be unrivaled in terms of processing cost, speed, and simplicity. The simplest of such devices consists of a single bulk-heterojunction (BHJ) active layer, in which the electron donor (conjugated polymer) and electron acceptor (fullerene) are deposited from a common solvent. The performance of BHJ solar cells is strongly correlated with the nanoscale structure of the active layer. Various processing techniques have been explored to improve the nanoscale morphology of the BHJ layer, e.g. by varying the casting solvent, thermal annealing, solvent annealing, and solvent additives. An understanding of the role of residual solvent in the BHJ layer is imperative in order to develop strategies for morphology stabilization and preserve the longevity of the device. This work highlights the effect of residual solvents on acceptor, (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) diffusion and ultimately the stability of the morphology. We first show that solvent is retained within the BHJ film despite prolonged heat treatment, leading to extensive phase separation between poly(3-hexylthiophene) (P3HT) and PCBM. We then show that the addition of a small volume fraction of nitrobenzene to the casting solution inhibits the diffusion of PCBM in the film and improves the fill factor of the BHJ device without further tempering. Other commonly used additives for morphology improvement were also investigated, i.e. 1,8-diiodooctane and 1-chloronaphthalene. We show that the choice of solvent additives has direct implications on morphological evolution, i.e. P3HT:PCBM BHJ films processed with a small amount of 1,8-diiodooctane or 1-chloronaphthalene have more crystalline PCBM domains compared to crystalline P3HT domains, while the opposite is true for films cast with nitrobenzene additive and films cast purely from chlorobenzene. The BHJ film cross-links when annealed at 300&degC in the presence of 1,8-diiodooctane. Cross-linking is found to occur even in pristine P3HT and PCBM films annealed under similar conditions.
520 $a Our work in understanding solvent interactions greatly facilitated our venture into multi-junction solution-processed devices. In our exploration of various device architectures for optimal performance, we have also established a way to modify the surface energy of a film to render it amenable to subsequent solution-processing. The tandem architecture offers a strategy to efficiently harvest photons from the full solar spectrum by stacking multiple photoactive layers with complementary absorption spectra. We found that the current predominant choices for solution-processed electron transport layer (ETL) each have their problems when implemented into a tandem device. Hence, we are presenting the novel use of stacked perovskite, (TBA,H)Ca2Nb3O 10 (CNO), semiconductor nanosheets as an ETL and we have successfully demonstrated a completely solution-processed tandem polymer solar cell. While further optimization of the CNO-layer is still required, the robust CNO-layer can be spin-coated on top of the BHJ photoactive layer and is stable towards subsequent processing and heat-treatment. We also explored the feasibility of introducing silver nanoparticles into the device structure via a low-cost solution-processable route for the exploitation of surface plasmon resonance for near-field absorption enhancement in the photoactive layer. We find that the photo-reduction of Ag+ to Ag appears to be a promising route for in-situ deposition of Ag nanoparticles.
590 $a School code: 0029.
650 4 $a Energy. $3 876794
650 4 $a Engineering, Chemical. $3 1018531
650 4 $a Engineering, Materials Science. $3 1017759
650 4 $a Chemistry, Polymer. $3 1018428
650 4 $a Alternative Energy. $3 1035473
690 $a 0791
690 $a 0542
690 $a 0794
690 $a 0495
690 $a 0363
710 2 $a University of California, Davis. $b Chemical Engineering. $3 2094245
773 0 $t Dissertation Abstracts International $g 74-10B(E).
790 $a 0029
791 $a Ph.D.
792 $a 2013
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3565489