Reported by Xin Jingming
Nowadays, non-fullerene polymer solar cells
(NF-PSCs) drew widely attentions from researchers and made a series of
progresses due to favorable performance. However, reasonable matching donor (D)
and acceptor (A) materials as well as quick optimization of blend film
morphology require continuous experimental and trial-and-error attempts within
tons of existing materials. In the meanwhile, morphological optimization is one
of the most significant processes during the fabrication. The charge mobility
and efficient diffusion length of exciton are directly determined by the
ordered packing of D/A molecular (crystallization) as well as phase separation
in blend film. Therefore, ideal morphology is an essential factor for enhancing
power conversion efficiency in PSCs. Currently, scientists mainly use X-ray
scattering techniques, generated by synchrotron facilities, to characterize the
active layer morphology of PSCs. Indeed, the researchers now need a rapid
characterizing method due to the limitation of synchrotron facilities.
Facing these scientific problems, the
researchers from organic photovoltaic materials & interface in State Key Laboratory
for Mechanical Behavior of Materials of Xi’an Jiaotong University ingenious applied
a parameter cold crystallization temperature (TCC) into PSCs which
is commonly used in polymer physics. Basically, slowly heating the materials in
quenched state will lead the movement of molecule chains and order packing with
heat release which can be recorded be differential scanning calorimeter (DSC).
With measurement of DSC, the TCC can be easily detected. The TCC can not only depict the complexity of acceptor molecular crystallization
in blend film, but also can present the distance to equilibrium state that is
quenched depth in polymer physics. The researchers selected the most
representative NF acceptor ITIC and blend with polymers with different degree
of crystallinity. The TCC of polymer:ITIC blend films were measured
and found that the more crystalline polymer presents lower TCC of
ITIC in the blend. Furthermore, synchrotron X-ray scattering techniques were
used to detected the phase separation information of blend films and
successfully correlated a linear relation between TCC and phase separation
which helps achieve the purpose of rapid morphology characterization. In
addition, the TCC was also corelated with performance and thermal
stability. This work used TCC to depict the phase separation in the
blend films and may direct the morphology optimization in the future.
These results were published of “Cold
Crystallization Temperature Correlated Phase Separation, Performance and
Stability of Polymer Solar Cells” on Matter which is a new sister
journal to Cell and Jouel from Cell Press focusing on materials
advancement and progression. Prof. Wei Ma from School of Material Science
Department of Material Physics and Chemistry is the corresponding author,
Jingming Xin and Xiangyi Meng are listed as co-first author who are graduate
students. The State Key Laboratory for Mechanical Behavior of Materials of
Xi’an Jiaotong University is the only one corresponding institute.
This work was supported by Ministry of
science and technology (No. 2016YFA0200700), NSFC (21504066, 21534003). The
project was supported by Open Research Fund of State Key Laboratory of Polymer
Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese
Academy of Sciences. Some of the data was obtained with the assistance of
Lawrence Berkeley National Laboratory Advanced Light Source, U.S. and Instrumental
Analysis Center of Xi'an Jiaotong University.
