Novel Series of Quasi-2D Ruddlesden−Popper Perovskites Based on
Short-Chained Spacer Cation for Enhanced Photodetection
Ruoting Dong,
†
Changyong Lan,
†,∥
Xiuwen Xu,
†
Xiaoguang Liang,
†,⊥
Xiaoying Hu,
∥
Dapan Li,
†,⊥
Ziyao Zhou,
†,⊥
Lei Shu,
†,‡,⊥
SenPo Yip,
†,‡,⊥
Chun Li,
∥
Sai-Wing Tsang,
†
and Johnny C. Ho*
,†,‡,§,⊥
†
Department of Materials Science and Engineering,
‡
State Key Laboratory of Millimeter Waves, and
§
Centre for Functional
Photonics, City University of Hong Kong, Kowloon 999077, Hong Kong
∥
School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610054, P.
R. China
⊥
Shenzhen Research Institute, City University of Hong Kong, Shenzhen 518057, P. R. China
*
S
Supporting Information
ABSTRACT: Quasi two-dimensional (2D) layered organic−inorganic perovskite materials (e.g., (BA)
2
(MA)
n−1
Pb
n
I
3n+1
;BA=
butylamine; MA = methylamine) have recently attracted wide attention because of their superior moisture stability as compared
with three-dimensional counterparts. Inevitably, hydrophobic yet insulating long-chained organic cations improve the stability at
the cost of hindering charge transport, leading to the unsatisfied performance of subsequently fabricated devices. Here, we
reported the synthesis of quasi-2D (iBA)
2
(MA)
n−1
Pb
n
I
3n+1
perovskites, where the relatively pure-phase (iBA)
2
PbI
4
and
(iBA)
2
MA
3
Pb
4
I
13
films can be obtained. Because of the shorter-branched chain of iBA as compared with that of its linear
equivalent (n-butylamine, BA), the resulting (iBA)
2
(MA)
n−1
Pb
n
I
3n+1
perovskites exhibit much enhanced photodetection
properties without sacrificing their excellent stability. Through hot-casting, the optimized (iBA)
2
(MA)
n−1
Pb
n
I
3n+1
perovskite films
with n = 4 give the significantly improved crystallinity, demonstrating the high responsivity of 117.09 mA/W, large on−off ratio
of 4.0 × 10
2
, and fast response speed (rise and decay time of 16 and 15 ms, respectively). These figure-of-merits are comparable
or even better than those of state-of-the-art quasi-2D perovskite-based photodetectors reported to date. Our work not only paves
a practical way for future perovskite photodetector fabrication via modulation of their intrinsic material properties but also
provides a direction for further performance enhancement of other perovskite optoelectronics.
KEYWORDS: quasi-2D, Ruddlesden−Popper perovskite, thin film, short-chained spacer, hot-cast, photodetection
■
INTRODUCTION
In recent years, three-dimensional (3D) organic−inorganic
halide perovskite materials, such as MAPbI
3
(MA = CH
3
NH
3
+
),
have attracted wide attention because of the fast development
of solar cells based on them.
1−4
Particularly, the power
conversion efficiency of these 3D hybrid halide perovskites
has been increased from 3.81 to 22.1% in just a few years.
5−8
Owing to the excellent light absorption coefficients, long charge
diffusion lengths, high carrier mobility, direct band gap, and low
rates of nonradiative charge recombination,
9, 10
organic−
inorganic halide perovskites also find extensive applications in
light-emitting diodes (LEDs),
11−13
photodetectors (PDs),
14,15
nanolasers,
16
transistors,
17
etc. However, these perov skite
materials still inevitably suffer from the inherent instability
over moisture, heat, and light, which seriously hampers their
practical utilizations.
18,19
At the same time, quasi two-dimensional (quasi-2D) layered
perovskite materials (also known as Ruddlesden−Popper, RP,
phases) have the crystal structure consisting of quasi-2D
perovskite slabs interleaved with cations,
20
in which they
generally adopt a chemical formula of L
2
A
n−1
B
n
X
3n+1
, where L is
a large size or long-chain organic cation, A is a regular cation, B
is a divalent metal cation, and X is a halide.
21−23
The variable n
is an integer, indicating the number of metal halide octahedral
Received: March 1, 2018
Accepted: May 9, 2018
Published: May 9, 2018
Research Article
www.acsami.org
Cite This: ACS Appl. Mater. Interfaces 2018, 10, 19019−19026
© 2018 American Chemical Society 19019 DOI: 10.1021/acsami.8b03517
ACS Appl. Mater. Interfaces 2018, 10, 19019−19026