Hybrid-type white LEDs based on inorganic halide
perovskite QDs: candidates for wide color gamut
display backlights
CHIH-HAO LIN,
1
AKTA VERMA,
2
CHIEH-YU KANG,
1
YUNG-MIN PAI,
1
TZU-YU CHEN,
1
JIN-JIA YANG,
1
CHIN-WEI SHER,
3
YA-ZHU YANG,
4
PO-TSUNG LEE,
1
CHIEN-CHUNG LIN,
5
YU-CHUAN WU,
6,7
S. K. SHARMA,
2
TINGZHU WU,
8,9
SHU-RU CHUNG,
4,10
AND HAO-CHUNG KUO
1,11
1
Department of Photonics and Institute of Electro-Optical Engineering, College of Electrical and Computer Engineering,
Taiwan Chiao Tung University, Hsinchu 30010, China
2
Department of Applied Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad-826004, India
3
Fok Ying Tung Research Institute, Hong Kong University of Science and Technology, Hong Kong, China
4
Department of Materials Science and Engineering, Taiwan Formosa University, Yunlin 63201, China
5
Institute of Photonic System, College of Photonics, Taiwan Chiao Tung University, Tainan 711, China
6
Department of Materials and Mineral Resources Engineering, Taiwan Taipei University of Technology, Taipei 10608, China
7
Department of Chemical and Materials Engineering, Chinese Culture University, Taipei 11114, China
8
Department of Electronic Science, Fujian Engineering Research Center for Solid-state Lighting, Collaborative Innovation Center for
Optoelectronic Semiconductors and Efficient Devices, Xiamen University, Xiamen 361005, China
9
e-mail: wutingzhu@xmu.edu.cn
10
e-mail: srchung@nfu.edu.tw
11
e-mail: hckuo@faculty.nctu.edu.tw
Received 28 December 2018; revi sed 3 Februar y 2019; ac cepted 11 Marc h 2019; posted 14 March 2019 (Doc. ID 356364 );
published 30 April 2019
We demonstrate inorganic halide perovskite quantum-dots-based white light-emitting diodes via three different geom-
etries, including liquid, solid, and hybrid types. Problems of fast anion exchange and aggregation in the cases of liquid-
and solid-type devices are discussed in detail and push us to move towards the fabrication of a hybrid-type device
structure. The experiment results illustrate that a hybrid-type device has the highest luminance efficiency (51 lm/
W) and a wide color gamut (122% of NTSC and 91% of Rec. 2020). Therefore, we conclude that a hybrid-type device
can provide an outstanding color gamut for high color gamut display applications.
© 2019 Chinese Laser Press
https://doi.org/10.1364/PRJ.7.000579
1. INTRODUCTION
Recently, popularity of colloidal quantum dots (QDs) and their
association in optoelectronic device applications such as light
emitting diodes (LEDs), photovoltaics, and photo-detectors
has increased rapidly [1–5]. For the past decade, LEDs have
received great attention because of their energy-saving capabil-
ity, in both the research community and industry [6–9].
Further, QDs are rising as excellent materials for white LED
(WLED) applications because of their various unique proper-
ties such as broad absorption band, narrow emission peak, and
wavelength-dependent size [3,10,11]. The main advantages of
QD-based WLEDs over conventional WLEDs and organic
LEDs (OLEDs) are high color purity with low cost production
[12,13]. In addition to these properties, high quantum yields
(QYs) and good spectral overlap show great potential towards
improvement in the efficiency of WLEDs [14]. All these char-
acteristics make QDs highly significant emerging candidates for
the development of next-generation display technologies [15].
In 1994, Colvin et al. reported the first CdSe QDs-based LEDs
[16]. In the last few years, halide perovskite QDs (PQDs) have
been demonstrated as amazing semiconductors for lighting ap-
plication [17,18]. Also, PQDs have potential to combine with
flexible technology [19,20]. Recently, the Liu group reported
the color gamut can be achieved at 113% of NTSC by using
the halide PQDs [21]. However, PQDs still have problems
in practical applications, such as instability, anion-exchange
reaction, intrinsic QD surface oxidation, photo bleaching,
and aggregation. The two major issues that limit practical ap-
plications are their instability and anion-exchange reaction
when different halide PQDs mix together [22,23]. Hence, we
attempt to enhance the performance for practical applications
based on the target for improving the main issues. Recently,
two-dimensional PQDs have attracted attention due to their
superior stabilities as photovoltaic devices [24–26]. In display
application, it is important to develop a suitable packaging type
Research Article
Vol. 7, No. 5 / May 2019 / Photonics Research 579
2327-9125/19/050579-07 Journal © 2019 Chinese Laser Press