Organic and Hybrid Solar Cells

342 Pages·2014·17.235 MB·English

by  Hui Huang, Jinsong Huang (eds.)

Organic and Hybrid Solar Cells
Hui Huang Jinsong Huang
●
Editors
Organic and Hybrid
Solar Cells
1 3
Editors
Hui Huang Jinsong Huang
College of Materials Science and Mechanical & Materials Engineering
Opto-electronic Technology University of Nebraska
University of Chinese Academy of Sciences Lincoln
Beijing Nebraska
China USA
ISBN 978-3-319-10854-4 ISBN 978-3-319-10855-1 (eBook)
DOI 10.1007/978-3-319-10855-1
Springer Cham Heidelberg New York Dordrecht London
Library of Congress Control Number: 2014955100
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Contents
1 Introduction to Organic Solar Cells ....................................................... 1
Hui Huang and Wei Deng
2 Charge Transport and Recombination
in Organic Solar Cells (OSCs) ................................................................ 19
Nanjia Zhou and Antonio Facchetti
3 Donor Materials for Organic Solar Cell (OSC) .................................... 53
Jinsheng Song and Zhishan Bo
4 n-Type Electron-Accepting Materials for
Organic Solar Cells (OSC) ...................................................................... 97
Yan Zhou, Jongbok Lee and Lei Fang
5 Interfacial Layers in Organic Solar Cells .............................................. 121
Jiarong Lian, Yongbo Yuan, Edwin Peng and Jinsong Huang
6 A lternative Electrodes for OSC .............................................................. 177
Yong Zhang and Bryce Nelson
7 I nverted Organic Solar Cells (OSCs) ..................................................... 215
Zhigang Yin, Shan-Ci Chen and Qingdong Zheng
8 S tability of Organic Solar Cells (OSCs) ................................................. 243
Yongye Liang and Xugang Guo
9 R esearch Progress and Manufacturing Techniques for
Large-Area Polymer Solar Cells ............................................................. 275
Ziyi Ge, Shaojie Chen, Ruixiang Peng and Amjad Islam
10 C olloidal Inorganic–Organic Hybrid Solar Cells ................................. 301
D. M. Balazs, M. J. Speirs and M. A. Loi
v
Contributors
D. M. Balazs Zernike Institute for Adavanced Materials, University of
Groningen, Nijenborgh, Groningen, Netherlands
Zhishan Bo Beijing Key Laboratory of Energy Conversion and Storage
Materials, College of Chemistry, Beijing Normal University, Beijing, No. 19
XinJieKouWai St, HaiDian District, China
Shan-Ci Chen State Key Laboratory of Structural Chemistry, Fujian Institute
of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou,
Fujian, P. R. China
Shaojie Chen Ningbo Institute of Materials Technology & Materials, Chinese
Academy of Sciences, Ningbo, Zhejiang, P.R. China
Wei Deng Department of Chemistry, Renmin University, Beijing, China
Antonio Facchetti Department of Chemistry, Northwestern University,
Evanston, IL, USA
Lei Fang Department of Chemistry, Texas A&M University, College Station,
TX, USA
Ziyi Ge Ningbo Institute of Materials Technology & Materials, Chinese
Academy of Sciences, Ningbo, Zhejiang, P.R. China
Xugang Guo Department of Materials Science and Engineering, South
University of Science and Technology of China, Shenzhen, Guangdong, China
Hui Huang College of Materials Science and Opto-electronic Technology,
University of Chinese Academy of Sciences, Beijing, 19A Yuquan Road,
Shijingshan District, China
Jinsong Huang Department of Mechanical and Materials Engineering and
Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln,
Lincoln, NB, USA
Amjad Islam Ningbo Institute of Materials Technology and Engineering,
Chinese Academy of Sciences, Ningbo, Zhejiang, P.R. China
vii
viii Contributors
Jongbok Lee Department of Chemistry, Texas A&M University, College
Station, TX, USA
Jiarong Lian Department of Mechanical and Materials Engineering and
Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln,
Lincoln, NB, USA
Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education
and Guangdong Province, College of Optoelectronic Engineering, Shenzhen
University, Shenzhen, China
Yongye Liang Department of Materials Science and Engineering, South
University of Science and Technology of China, Shenzhen, Guangdong, China
M. A. Loi Zernike Institute for Adavanced Materials, University of Groningen,
Nijenborgh, Groningen, Netherlands
Bryce Nelson Bryce Nelson Sigma-Aldrich Corporation, Materials Science,
Milwaukee, WI, USA
Edwin Peng Department of Mechanical and Materials Engineering and
Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln,
Lincoln, NB, USA
Ruixiang Peng Ningbo Institute of Materials Technology and Engineering,
Chinese Academy of Sciences, Ningbo, Zhejiang, P.R. China
M. J. Speirs Zernike Institute for Adavanced Materials, University of
Groningen, Nijenborgh, Groningen, Netherlands
Zhigang Yin State Key Laboratory of Structural Chemistry, Fujian Institute
of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou,
Fujian, P. R. China
Yongbo Yuan Department of Mechanical and Materials Engineering and
Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln,
Lincoln, NB, USA
Yong Zhang Sigma-Aldrich Corporation, Materials Science, Milwaukee, WI,
USA
Qingdong Zheng State Key Laboratory of Structural Chemistry, Fujian Institute
of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou,
Fujian, P. R. China
Nanjia Zhou Department of Materials Science and Engineering, Northwestern
University, Evaston, IL, USA
Yan Zhou Department of Chemical Engineering, Stanford University, Stanford,
CA, USA
Chapter 1
Introduction to Organic Solar Cells
Hui Huang and Wei Deng
1.1 Introduction
In the recent years, solar cells play an important role in meeting the global energy
and environment challenges as a clean and sustainable source of energy [1]. The
first generation of solar technologies is wafer-size single-junction solar cells based
on crystalline silicon that are assembled into large area modules [2]. However, the
electricity generated by silicon solar cells is more expensive than the grid due to
their high cost of manufacture and long energy payback time. This drives the com-
munity to search new materials and devices in order to further reduce the cost of
produced electricity. Thin-film photovoltaics are second-generation solar technolo-
gies [3] based on inorganic semiconductor materials including amorphous silicon
II–VI semiconductors such as CdS or CdTe and chalcogenides such as CuInSe or
2
CuInGaSe [4]. The third generation solar technologies include: (i) the dye-sensi-
2
tized solar cells that are electrochemical cells with an electrolyte [5]; (ii) organic
solar cells(OSCs) that include semiconducting donor and acceptor composite and
function based on excitonic mechanism [6, 7]; (iii) hybrid solar cells where inor-
ganic quantum dots are doped into organic semiconductors or by combining nano-
structured inorganic semiconductors with organic materials [8, 9].
The first conceptual OSCs were reported by Kearns and Calvin in 1958 that have
a pristine organic material (magnesium phthalocyanine) between two electrodes
[10]. However, the power conversion efficiency (PCE) stayed in the order 0.1 % or
lower for more than 20 years. In 1986, Tang developed bilayer heterojunction OSCs
with a PCE of about 1 % which represented a major milestone for OSCs [6]. Later
H. Huang ()
College of Materials Science and Opto-electronic Technology, University of Chinese Academy
of Sciences, 19A Yuquan Road, Shijingshan District, 100049 Beijing, China
e-mail: [email protected]
W. Deng
Department of Chemistry, Renmin University, 100049 Beijing, China
© Springer International Publishing Switzerland 2014 1
H. Huang, J. Huang (eds.), Organic and Hybrid Solar Cells,
DOI 10.1007/978-3-319-10855-1_1
2 H. Huang and W. Deng

E
π*
LUMO
π
HOMO
Fig. 1.1  Illustration of HOMO and LUMO energy levels of an organic semiconductor
on bulk heterojunction OSCs [7] paved the path for achieving high efficiency OSCs
that now passed over 10 % efficiency [11], reaching the dawn of commercialization.
Even though their efficiency and stability are still under intense investigations,
the organic solar technologies have several advantages compared to their inorganic
counterparts: (i) the solution processability of organic semiconductors provides a
great potential for low cost fabrication of large area OSCs; (ii) low temperature
processing reduces energy consumption during manufacturing, further decreasing
the energy payback time; (iii) the capability of printing on top of plastic substrates
results in applications such as portable electronics. In this chapter, the basic prin-
ciples including organic materials’ working mechanism, device configurations and
characterizations, and device stability will be described.
1.2 Materials
Organic semiconductors can be generally classified into two categories: small mol-
ecules or oligomers and polymers. Both, molecular and polymeric semiconductors,
are carbon-based materials that present a backbone along which the carbon (or ni-
trogen, oxygen, sulfur, etc.) atoms are sp2-hybridized, and thus remain a p-atomic
orbital. The overlap of these p-orbitals along the backbone leads to the formation
of delocalized π molecular orbitals. The overlap of different electron wave func-
tions of neighboring atoms defines the frontier electronic levels: the Highest Oc-
cupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital
(LUMO). As shown in Fig. 1.1, the HOMO with filled electrons has different en-
ergy levels from the LUMO free of electrons, which determine the optical and elec-
trical properties of the semiconductors.
1 Introduction to Organic Solar Cells 3
In general, organic semiconductors can be treated as “intrinsic wide band gap
semiconductors” (band gaps above 1.4 eV) down to “insulators” (band gap above
3 eV) with a negligibly low intrinsic charge carrier density at room temperature in
the dark. Extrinsic charge carriers are introduced into organic semiconductors upon
chemical photochemical or electrochemical doping [12]. The charge carrier mobil-
ity is an important parameter of organic semiconductors. The overlap of the frontier
π molecular orbitals between adjacent molecules or polymer chains represents the
strength of the intermolecular electronic couplings and governs charger carrier mo-
bilities in organic semiconductors. The localization of charge carrier and formation
of polarons results in a rather low carrier mobilities compared to those of inorganic
counterparts. The carrier transport then relies on polarons hopping from molecule
to molecule [13]. Due to this hopping mechanism, the charge carrier mobilities
are determined by many factors including molecular packing [14], disorder [15],
temperature [16], presence of impurities [17], charge carrier density [18], electric
field [19], size/molecular weight [20, 21], and pressure [22]. As a result, the mor-
phology of the organic semiconductor films can significantly influence the charge
carrier mobilities that can vary over several orders of magnitude when changing
from highly disordered amorphous materials to highly ordered crystalline films
[13]. There are several techniques to measure the carrier mobilities [23], such as
time of flight (TOF) [24, 25], pulse-radiolysis time-resolved microwave conductiv-
ity (PR-TRMC) [26], field-effect transistor (FET) [27], and space-charge-limited
current (SCLC) [28]. The mobilities measured with SCLC techniques reflect the
bulk mobilities of organic semiconductors in OSCs.
OSCs materials include hole-conducting p-type semiconductors and electron-
conducting n-type semiconductors together with interfacial layer materials. The p-
type materials include small molecular and polymeric semiconductors. The classic
small molecules include porpyrins, phthalocyanines, and so on. Compared to the
polymeric analogues, the small molecules enjoy high purity and strong molecular
organization into ordered structures leading to high charge carrier mobility. The first
OSC is based on small molecule of magnesium phthalocyanine [10]. The efficien-
cy of small molecule-based OSCs used to be much behind that of polymer-based
OSCs. Recently, the efficiency dramatically increased to over 10 % upon employing
conjugated small molecules with a tandem device configuration [29]. The polymer
semiconductors are the dominant p-type materials due to their solution processabil-
ity and diversity of structures. The donor–acceptor (D–A) alternating strategy is the
broadly used method to tune the energy levels of polymeric semiconductors. Thus,
hundreds of novel polymeric p-type materials have been designed, synthesized, and
used in OSCs studies resulting in efficiency over 10 % [11]. The dominant n-type
materials are fullerene derivatives due to their triplet degeneration of LUMO [30],
fast charge splitting [31], and good electron mobility [32]. However, their weak ab-
sorption in the visible region rooted from their symmetric forbidden properties [33,
34] inspired the discovery of novel non-fullerene acceptors. Interfacial layer materi-
als can be classified as different categories according to their functions including
electron collection, layer hole collection, layer exciton dissociation, layer morphol-
ogy control, layer light harvesting layer, and interconnecting layer for tandem solar
cells.