aim of GIWAXS

molecular packing information/mechanism

evidence

two-dimensional (2D) GIWAXS patterns and the corresponding out-of-plane (qz) and in-plane (qr) intensity profiles

Th corresponding intensity profiles of the blend films along (g) the qz axis and (h) the qr axis

scattering pattern indexing

For ITIC-Th (Figure 1c), the diffraction peaks located at (qr, qz) of (0.470, 0), (0.940, 0), and (1.41, 0) Å−1 are indexed as (100), (200), and (300) peaks, corresponding to the in-plane lamellar stacking of ITIC-Th with a lattice constant of a = 13.4 Å.

It is also straightforward to index the diffraction peak at (0, 1.79) Å−1 as the (010) peak, associated with the π–π stacking (b = 3.51 Å) of ITIC-Th in the out-of-plane direction.

lattice constant calculation

lattice constant = $2\pi$/peak position

Since (100)′ is too close to the beam stop, the lattice constant is calculated from the peak position of (200)′, which is at (0, 0.530) Å−1, corresponding to a relatively smaller lattice constant a′ ≈ 23.7 Å.

bimodal lamellar stacking

Besides, there appears a very bright off-axis diffraction peak at (0.168, 0.439) Å−1, which is along the (100) lamellar ring with an angle of ≈21° with respect to the qz axis. The peak corresponds to the lamellar stacking of nearly edge-on oriented ITICTh crystallites tilted ≈21° from the surface normal. Therefore, it implies that ITIC-Th shows a bimodal lamellar stacking in both face-on and tilted edge-on orientations in the pure thin film.

peak difference

Though differing merely in the side chain structure (hexylphenyl for ITIC and thienyl for ITIC-Th), ITIC-Th exhibits much brighter and sharper scattering peaks, demonstrating a higher degree of crystallinity, compared with ITIC which instead displays relatively weaker and broader scattering features.

Furthermore, the scattering peaks span narrower polar angle ranges (Figure S2) compared to the binary FTAZ:IDIC film, indicating that a remarkable enhancement of edge-on orientational order has been induced through the incorporation of INIC3.

oritentation

Together, it suggests that ITIC-Th crystalline domains in the pure film are predominantly “face-on” orientated, in agreement with previous reports.

relation with mobility

Owing to the anisotropic mobility of organic semiconductor crystal packing,[29] we could establish the correlations between the backbone or face-on ordering and the electron mobility (μe) in the in-plane or the out-of-plane directions via field-effect transistors (FETs) and electron-only devices respectively.[30–33]

The in-plane μe of the ternary PBDBT: ITIC:ITIC-Th film is about an order of magnitude higher than the in-plane μe of both binary controls, in accordance with the enhanced backbone ordering which is along the in-plane direction.

Although the out-of-plane charge mobility is known to be crucial in solar cells as the net charge transport direction is out-of-plane, a higher in-plane charge mobility can expedite charges to find their way out, in turn contributing to the increase of FF.

拟合方法

Gauss函数(area version of Gaussian function)，具体见https://blog.csdn.net/Jelly_Zhou/article/details/126110781.
https://www.zhihu.com/question/316010845

Reference

J. Q. Mai, Y. Q. Xiao, G. D. Zhou, J. Y. Wang, J. S. Zhu, N. Zhao, X. W. Zhan and X. H. Lu, Hidden Structure Ordering Along Backbone of Fused-Ring Electron Acceptors Enhanced by Ternary Bulk Heterojunction, ADVANCED MATERIALS, 2018, 30(34): 1802888. (DOI: https://doi.org/10.1002/adma.201802888)

Y. Xiao and X. Lu, Morphology of organic photovoltaic non-fullerene acceptors investigated by grazing incidence X-ray scattering techniques, Materials Today Nano, 2019, 5((DOI: https://doi.org/10.1016/j.mtnano.2019.100030)

A. Mahmood and J. L. Wang, A Review of Grazing Incidence Small‐ and Wide‐Angle X‐Ray Scattering Techniques for Exploring the Film Morphology of Organic Solar Cells, Solar RRL, 2020, 4(10). (DOI: https://doi.org/10.1002/solr.202000337)

Y. Q. Xiao, R. J. Ma, G. D. Zhou, J. S. Zhu, T. K. Lau, S. X. Dai, J. J. Rech, N. Zhao, W. You, H. Yan, X. W. Zhan and X. H. Lu, Ternary Blending Driven Molecular Reorientation of Non-Fullerene Acceptor IDIC with Backbone Order, ACS APPLIED ENERGY MATERIALS, 2020, 3(11): 10814. (DOI: https://doi.org/10.1021/acsaem.0c01858)