Defects Passivation With Dithienobenzodithiophene-
based
π-conjugated Polymer for Enhanced Performance
of Perovskite Solar Cells
Xianqiang Li, Wenhui Li, Yijie Yang, Xue Lai, Qiang Su, Dan Wu, Gongqiang Li,*
Kai Wang, Shuming Chen, Xiao Wei Sun, and Aung Ko Ko Kyaw*
A dithienobenzodithiophene-based π-conjugated polymer consisting of
fluorinated benzotriazole and benzothiadiazole is successfully applied
through anti-solvent method to passivate the defects of perovskite crystals.
The fluorinated polymer interacts with under coordina ted Pb
2þ
ions in the
perovskite crystals to form Pb-F bond which effectively passivates t he
defects. The trap density is reduced and the charge carrier transfer between
the perovskite film and Spi ro-OMeTAD is also improved after passivation
with the polymer. As a re sult, a power conversion efficiency (PCE) of
18.03% is achieved in the champion c ell. After storing in an ambient
environment with 60% relative humidity for 1000 h, the device still retains
90% of the original PC E. These resul ts demonstrate that dithienobenzodi-
thiophene-based
π-conjugated polymers are promising materials for passiv-
ation of pero vskite films to further improve the performance and stability of
perovskite solar cells.
1. Introduction
In recent years, a new emerging photovol-
taic technology, which uses the solution-
processed organic–inorganic lead halide
perovskite as a light absorber, has attracted
lots of attentions. Compared to the domi-
nant photovoltaic technology based on
inorganic materials such as Si and GaAs,
the perovskite solar cells (PSCs) have
several advantages: low-cost fabrication
process, mechanical flexibility, solution
processability, and compatibility with roll-
to-roll fabrication process.
[1–3]
Moreover,
the power conversion efficiency (PCE) of
PSCs experienced a skyrocketing increase.
In just within a decade, the PCE was
enhanced from 3.8% in 2009
[4]
to 23.7%
recently.
[5]
Despite the rapid development,
the commercialization of PSC is still
challenging. In most of the PSCs, the perovskite films are
prepared by solution processes, such as one-step spin coating,
[6,7]
sequential deposition,
[8]
vapor assisted solution process,
[9]
etc.
However, the solution-processed polycrystalline perovskite films
contain lots of defects at the surface and grain boundaries (GBs)
although bulk-defect is not serious owing to its defect tolerance
nature arrives from the low crystallization temperature. In the
polycrystalline perovskite films, the defects could form electronic
trap states,
[10–12]
limit lateral diffusion of carriers,
[13]
reduce
charge carrier lifetime, and cause ion diffusion and migra-
tion,
[14,15]
thus limiting the efficiency and stability of PSCs.
Therefore, passivating defects at the surface and GBs within
perovskite films becomes important for achieving the high
performance of PSCs.
[16–18]
Among the various perovskite deposition techniques, one-
step spin coating technique with anti-solvents (chlorobenzene
(CB), toluene, etc.) has been widely used for achieving the high-
efficiency PSCs because it is one of the effective methods and can
produce uniform and high-quality perovskite films.
[19–22]
However, efforts must be made to suppress the defects to
further improve the performance and stability of PSCs. D. Bi
et al. introduced an insulator, PMMA, into anti-solvent (CB/
toluene) to enable much faster heterogeneous nucleation of
perovskite crystals, thus resulting in smooth perovskite films
with fewer defects and larger oriented grains.
[23]
Wu et al. used
[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in toluene as
Dr. X. Li
[+]
, Dr. W. Li
[+]
, Dr. Y. Yang, X. Lai, Q. Su, Dr. D. Wu,
Prof. K. Wang, Prof. S. Chen, Prof. X. W. Sun, Prof. A. K. K. Kyaw
Guangdong University Key Laboratory for Advanced Quantum Dot
Displays and Lighting
Department of Electrical & Electronic Engineering
Southern University of Science and Technology
Shenzhen 518055, P. R. China
E-mail: aung@sustc.edu.cn
X. Lai, Prof. G. Li
Key Laboratory of Flexible Electronic (KLOFE) & Institute of Advanced
Materials (IAM)
Jiangsu National Synergistic Innovation Center for Advanced Materials
(SICAM)
Nanjing Tech University
30 South Puzhu Road, Nanjing 211816, P. R. China
E-mail: iamgqli@njtech.edu.cn
Prof. K. Wang, Prof. X. W. Sun, Prof. A. K. K. Kyaw
Shenzhen Planck Innovation Technologies Pte Ltd.
Ganli 6th Road, Longgang, Shenzhen 518112, P. R. China
The ORCID identification number(s) for the author(s) of this article
can be found under https://doi.org/10.1002/solr.201900029.
[þ]
Dr. X. Li and Dr. W. Li contributed equally to this work.
DOI: 10.1002/solr.201900029
Defects Passivation www.solar-rrl.com
FULL PAPER
Sol. RRL 2019, 1900029 © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim1900029 (1 of 9)