1
Scientific RepoRts | 6:23916 | DOI: 10.1038/srep23916
www.nature.com/scientificreports
Highly ecient organic tandem
solar cell with a SubPc interlayer
based on TAPC:C
70
bulk
heterojunction
Yuan Gao
1,2
, Fangming Jin
1,2
, Wenlian Li
1
, Zisheng Su
1
, Bei Chu
1
, Junbo Wang
1
,
Haifeng Zhao
1
, Hairuo Wu
1,2
, Chengyuan Liu
1,2
, Fuhua Hou
1,2
, Tong Lin
1,2
& Qiaogang Song
1,2
We report a small molecule tandem organic photovoltaic (OPV) cell with a high power conversion
eciency (PCE) of 7.27%. This cell contains two subcells with an identical mixed active layer of
C
70
:5 wt%TAPC (1,1-bis-(4-bis(4-methyl-phenyl)-amino-phenyl)-cyclohexane). The performance was
dramatically improved by simply inserting a thin boron subphthalocyanine chloride (SubPc) interlayer,
which results in an increase of the short-circuit current and open-circuit voltage as well as a decrease of
the series resistance of the tandem cell. The response of the cell only contributed from the absorption of
C
70
. The high PCE was attributed to the high absorption eciency of C
70
and improved holes extraction
eciency at the anode due to the band bending occurs at both MoO
3
/SubPc and SubPc/C
70
:5 wt%TAPC
interfaces.
Over the past few years, organic photovoltaic (OPV) cells have drawn a great deal of attention in both funda-
mental research and industrial elds. OPV cell is one of the most-promising next-generation energy-harvesting
technologies because it has the advantages of low weight, exible form factor, low-cost mass production and low
energy consumption in manufacturing processes
1–8
. Recently, the power conversion eciency (PCE) of the OPV
cells has exceeded 10%, which is a milestone development for valuable commercial applications
9,10
. In spite of
this, there are some factors limit the performance of OPV cells such as low light absorption and charge carrier
collection eciencies. A tandem cell architecture is usually adopted to increase the absorption and hence the
performance of OPV cells. Besides, the architecture of tandem cells should be precisely designed to guaran-
tee a high charge carrier collection eciency. Typically, tandem cells are constructed by series stacking two or
more subcells with complementary absorption spectra because the overall light absorption could be enhanced.
As a result of such a design, a matched photocurrent resulted from the individual subcell was extracted
11
. e
subcells with identical compositions have also been used in tandem structure, but the PCE of these cells was
generally lower
12,13
. Zhang et al.
13
reported a tandem cell with the same subcell units of MoO
3
/C
60
:5 wt% 1,1-bis-
(4-bis(4-methyl-phenyl)-amino-phenyl)-cyclohexane (TAPC). is subcell structure was similar to their previ-
ous reported OPV cells
14
, in which the open circuit voltage (Voc) was mainly determined by the MoO
3
/C
60
:TAPC
Schottky barrier
15
and the short circuit current (Jsc) was primary originated from the absorption of the fullerene.
is tandem OPV cells had a lower PCE of 4.12%. is should be attributed the low absorption eciency of C
60
and low charge carrier collection eciency of this device
13
. In one of our previous works, we have observed a
considerable improved PCE of the OPV cell when a thin boron subphthalocyanine chloride (SubPc) interlayer
was inserted between ITO/MoO
3
and bulk heterojunction (BHJ) of TAPC:C
60
16
. A high hole extraction eciency
has been obtained in planar heterojunction (PHJ) OPV cells with SubPc and fullerene materials as the donor
and acceptor, respectively
17,18
. Because SubPc has a deep highest occupied molecular orbital (HOMO) level (i.e.,
higher ionization potential), a signicant band bending towards the gap states in the MoO
3
layer
18
due to interface
dipole eect can be observed at the MoO
3
/SubPc interface
17,19
. Such an energy level alignment allows more e-
cient holes extraction of the devices
17
. C
70
fullerene has comparable electronic properties but a higher extinction
1
State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics, and
Physics, Chinese Academy of Sciences, Changchun 130033, People’s Republic of China.
2
University of Chinese
Academy of Sciences, Beijing 100039, People’s Republic of China. Correspondence and requests for materials should
be addressed to W.L. (email: wllioel@aliyun.com) or Z.S. (email: suzs@ciomp.ac.cn)
Received: 17 November 2015
Accepted: 16 March 2016
Published: 01 April 2016
OPEN