Controlled conjugated backbone twisting for an increased open-circuit voltage while having a high short-circuit current in poly(hexylthiophene) derivatives

Sangwon Ko; Eric T. Hoke; Laxman Pandey; Sanghyun Hong; Rajib Mondal; Chad Risko; Yuanping Yi; Rodrigo Noriega; Michael D. McGehee; Jean-Luc Bredas; Alberto Salleo; Zhenan Bao

doi:10.1021/ja210954r

Controlled conjugated backbone twisting for an increased open-circuit voltage while having a high short-circuit current in poly(hexylthiophene) derivatives

Sangwon Ko, Eric T. Hoke, Laxman Pandey, Sanghyun Hong, Rajib Mondal, Chad Risko, Yuanping Yi, Rodrigo Noriega, Michael D. McGehee, Jean-Luc Bredas, Alberto Salleo, Zhenan Bao^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

188 Scopus citations

Abstract

Conjugated polymers with nearly planar backbones have been the most commonly investigated materials for organic-based electronic devices. More twisted polymer backbones have been shown to achieve larger open-circuit voltages in solar cells, though with decreased short-circuit current densities. We systematically impose twists within a family of poly(hexylthiophene)s and examine their influence on the performance of polymer:fullerene bulk heterojunction (BHJ) solar cells. A simple chemical modification concerning the number and placement of alkyl side chains along the conjugated backbone is used to control the degree of backbone twisting. Density functional theory calculations were carried out on a series of oligothiophene structures to provide insights on how the sterically induced twisting influences the geometric, electronic, and optical properties. Grazing incidence X-ray scattering measurements were performed to investigate how the thin-film packing structure was affected. The open-circuit voltage and charge-transfer state energy of the polymer:fullerene BHJ solar cells increased substantially with the degree of twist induced within the conjugated backbone-due to an increase in the polymer ionization potential-while the short-circuit current decreased as a result of a larger optical gap and lower hole mobility. A controlled, moderate degree of twist along the poly(3,4-dihexyl-2,2′:5′,2′′- terthiophene) (PDHTT) conjugated backbone led to a 19% enhancement in the open-circuit voltage (0.735 V) vs poly(3-hexylthiophene)-based devices, while similar short-circuit current densities, fill factors, and hole-carrier mobilities were maintained. These factors resulted in a power conversion efficiency of 4.2% for a PDHTT:[6,6]-phenyl-C ₇₁-butyric acid methyl ester (PC ₇₁BM) blend solar cell without thermal annealing. This simple approach reveals a molecular design avenue to increase open-circuit voltage while retaining the short-circuit current.

Original language	English (US)
Pages (from-to)	5222-5232
Number of pages	11
Journal	Journal of the American Chemical Society
Volume	134
Issue number	11
DOIs	https://doi.org/10.1021/ja210954r
State	Published - Mar 21 2012
Externally published	Yes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-C1-015-21
Acknowledgements: This publication was partially based on work supported by the Center for Advanced Molecular Photovoltaics, Award No. KUS-C1-015-21, made by King Abdullah University of Science and Technology (KAUST). Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. Computational resources were partly made available through the CRIF Program of the NSF (Award No. CHE-0946869). E.T.H. was supported by the Fannie and John Hertz Foundation. We thank Michael F. Toney and Eric Verploegen for helpful discussions.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

ASJC Scopus subject areas

General Chemistry
Biochemistry
Catalysis
Colloid and Surface Chemistry

Access to Document

10.1021/ja210954r

Cite this

Ko, S., Hoke, E. T., Pandey, L., Hong, S., Mondal, R., Risko, C., Yi, Y., Noriega, R., McGehee, M. D., Bredas, J.-L., Salleo, A., & Bao, Z. (2012). Controlled conjugated backbone twisting for an increased open-circuit voltage while having a high short-circuit current in poly(hexylthiophene) derivatives. Journal of the American Chemical Society, 134(11), 5222-5232. https://doi.org/10.1021/ja210954r

@article{eb100f27b59b47bd8da47ac3ae3bcd6d,

title = "Controlled conjugated backbone twisting for an increased open-circuit voltage while having a high short-circuit current in poly(hexylthiophene) derivatives",

abstract = "Conjugated polymers with nearly planar backbones have been the most commonly investigated materials for organic-based electronic devices. More twisted polymer backbones have been shown to achieve larger open-circuit voltages in solar cells, though with decreased short-circuit current densities. We systematically impose twists within a family of poly(hexylthiophene)s and examine their influence on the performance of polymer:fullerene bulk heterojunction (BHJ) solar cells. A simple chemical modification concerning the number and placement of alkyl side chains along the conjugated backbone is used to control the degree of backbone twisting. Density functional theory calculations were carried out on a series of oligothiophene structures to provide insights on how the sterically induced twisting influences the geometric, electronic, and optical properties. Grazing incidence X-ray scattering measurements were performed to investigate how the thin-film packing structure was affected. The open-circuit voltage and charge-transfer state energy of the polymer:fullerene BHJ solar cells increased substantially with the degree of twist induced within the conjugated backbone-due to an increase in the polymer ionization potential-while the short-circuit current decreased as a result of a larger optical gap and lower hole mobility. A controlled, moderate degree of twist along the poly(3,4-dihexyl-2,2′:5′,2′′- terthiophene) (PDHTT) conjugated backbone led to a 19% enhancement in the open-circuit voltage (0.735 V) vs poly(3-hexylthiophene)-based devices, while similar short-circuit current densities, fill factors, and hole-carrier mobilities were maintained. These factors resulted in a power conversion efficiency of 4.2% for a PDHTT:[6,6]-phenyl-C 71-butyric acid methyl ester (PC 71BM) blend solar cell without thermal annealing. This simple approach reveals a molecular design avenue to increase open-circuit voltage while retaining the short-circuit current.",

author = "Sangwon Ko and Hoke, {Eric T.} and Laxman Pandey and Sanghyun Hong and Rajib Mondal and Chad Risko and Yuanping Yi and Rodrigo Noriega and McGehee, {Michael D.} and Jean-Luc Bredas and Alberto Salleo and Zhenan Bao",

note = "KAUST Repository Item: Exported on 2020-10-01 Acknowledged KAUST grant number(s): KUS-C1-015-21 Acknowledgements: This publication was partially based on work supported by the Center for Advanced Molecular Photovoltaics, Award No. KUS-C1-015-21, made by King Abdullah University of Science and Technology (KAUST). Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. Computational resources were partly made available through the CRIF Program of the NSF (Award No. CHE-0946869). E.T.H. was supported by the Fannie and John Hertz Foundation. We thank Michael F. Toney and Eric Verploegen for helpful discussions. This publication acknowledges KAUST support, but has no KAUST affiliated authors.",

year = "2012",

month = mar,

day = "21",

doi = "10.1021/ja210954r",

language = "English (US)",

volume = "134",

pages = "5222--5232",

journal = "Journal of the American Chemical Society",

issn = "0002-7863",

publisher = "American Chemical Society",

number = "11",

}

Ko, S, Hoke, ET, Pandey, L, Hong, S, Mondal, R, Risko, C, Yi, Y, Noriega, R, McGehee, MD, Bredas, J-L, Salleo, A & Bao, Z 2012, 'Controlled conjugated backbone twisting for an increased open-circuit voltage while having a high short-circuit current in poly(hexylthiophene) derivatives', Journal of the American Chemical Society, vol. 134, no. 11, pp. 5222-5232. https://doi.org/10.1021/ja210954r

TY - JOUR

T1 - Controlled conjugated backbone twisting for an increased open-circuit voltage while having a high short-circuit current in poly(hexylthiophene) derivatives

AU - Ko, Sangwon

AU - Hoke, Eric T.

AU - Pandey, Laxman

AU - Hong, Sanghyun

AU - Mondal, Rajib

AU - Risko, Chad

AU - Yi, Yuanping

AU - Noriega, Rodrigo

AU - McGehee, Michael D.

AU - Bredas, Jean-Luc

AU - Salleo, Alberto

AU - Bao, Zhenan

N1 - KAUST Repository Item: Exported on 2020-10-01 Acknowledged KAUST grant number(s): KUS-C1-015-21 Acknowledgements: This publication was partially based on work supported by the Center for Advanced Molecular Photovoltaics, Award No. KUS-C1-015-21, made by King Abdullah University of Science and Technology (KAUST). Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. Computational resources were partly made available through the CRIF Program of the NSF (Award No. CHE-0946869). E.T.H. was supported by the Fannie and John Hertz Foundation. We thank Michael F. Toney and Eric Verploegen for helpful discussions. This publication acknowledges KAUST support, but has no KAUST affiliated authors.

PY - 2012/3/21

Y1 - 2012/3/21

N2 - Conjugated polymers with nearly planar backbones have been the most commonly investigated materials for organic-based electronic devices. More twisted polymer backbones have been shown to achieve larger open-circuit voltages in solar cells, though with decreased short-circuit current densities. We systematically impose twists within a family of poly(hexylthiophene)s and examine their influence on the performance of polymer:fullerene bulk heterojunction (BHJ) solar cells. A simple chemical modification concerning the number and placement of alkyl side chains along the conjugated backbone is used to control the degree of backbone twisting. Density functional theory calculations were carried out on a series of oligothiophene structures to provide insights on how the sterically induced twisting influences the geometric, electronic, and optical properties. Grazing incidence X-ray scattering measurements were performed to investigate how the thin-film packing structure was affected. The open-circuit voltage and charge-transfer state energy of the polymer:fullerene BHJ solar cells increased substantially with the degree of twist induced within the conjugated backbone-due to an increase in the polymer ionization potential-while the short-circuit current decreased as a result of a larger optical gap and lower hole mobility. A controlled, moderate degree of twist along the poly(3,4-dihexyl-2,2′:5′,2′′- terthiophene) (PDHTT) conjugated backbone led to a 19% enhancement in the open-circuit voltage (0.735 V) vs poly(3-hexylthiophene)-based devices, while similar short-circuit current densities, fill factors, and hole-carrier mobilities were maintained. These factors resulted in a power conversion efficiency of 4.2% for a PDHTT:[6,6]-phenyl-C 71-butyric acid methyl ester (PC 71BM) blend solar cell without thermal annealing. This simple approach reveals a molecular design avenue to increase open-circuit voltage while retaining the short-circuit current.

AB - Conjugated polymers with nearly planar backbones have been the most commonly investigated materials for organic-based electronic devices. More twisted polymer backbones have been shown to achieve larger open-circuit voltages in solar cells, though with decreased short-circuit current densities. We systematically impose twists within a family of poly(hexylthiophene)s and examine their influence on the performance of polymer:fullerene bulk heterojunction (BHJ) solar cells. A simple chemical modification concerning the number and placement of alkyl side chains along the conjugated backbone is used to control the degree of backbone twisting. Density functional theory calculations were carried out on a series of oligothiophene structures to provide insights on how the sterically induced twisting influences the geometric, electronic, and optical properties. Grazing incidence X-ray scattering measurements were performed to investigate how the thin-film packing structure was affected. The open-circuit voltage and charge-transfer state energy of the polymer:fullerene BHJ solar cells increased substantially with the degree of twist induced within the conjugated backbone-due to an increase in the polymer ionization potential-while the short-circuit current decreased as a result of a larger optical gap and lower hole mobility. A controlled, moderate degree of twist along the poly(3,4-dihexyl-2,2′:5′,2′′- terthiophene) (PDHTT) conjugated backbone led to a 19% enhancement in the open-circuit voltage (0.735 V) vs poly(3-hexylthiophene)-based devices, while similar short-circuit current densities, fill factors, and hole-carrier mobilities were maintained. These factors resulted in a power conversion efficiency of 4.2% for a PDHTT:[6,6]-phenyl-C 71-butyric acid methyl ester (PC 71BM) blend solar cell without thermal annealing. This simple approach reveals a molecular design avenue to increase open-circuit voltage while retaining the short-circuit current.

UR - http://www.scopus.com/inward/record.url?scp=84858650646&partnerID=8YFLogxK

U2 - 10.1021/ja210954r

DO - 10.1021/ja210954r

M3 - Article

C2 - 22385287

AN - SCOPUS:84858650646

SN - 0002-7863

VL - 134

SP - 5222

EP - 5232

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 11

ER -

Controlled conjugated backbone twisting for an increased open-circuit voltage while having a high short-circuit current in poly(hexylthiophene) derivatives

Abstract

Bibliographical note

ASJC Scopus subject areas

Access to Document

Other files and links

Fingerprint

Cite this