Unambiguous determination of molecular packing in crystalline donor domains of small molecule solution processed solar cell devices using routine X-ray diffraction techniques

Cyano-substitution on the end-capping group: facile access toward asymmetrical squaraine showing strong dipole–dipole interactions as a high performance small molecular organic solar cells material

“…The representative data of these devices were summarized in Table 4, the current density-voltage (J-V) curves as well as the external quantum efficiency (EQE) spectra were shown in Fig. The 0.10 V higher V oc of the ASQ-5-CN-device relative to the 14 reference device was consistent with the 0.11 eV decreased HOMO energy level of ASQ-5-CN than that of ASQ-5. The 0.10 V higher V oc of the ASQ-5-CN-device relative to the 14 reference device was consistent with the 0.11 eV decreased HOMO energy level of ASQ-5-CN than that of ASQ-5.…”

Understanding the Limiting Factors of Solvent‐Annealed Small‐Molecule Bulk‐Heterojunction Organic Solar Cells from a Chemical Perspective

“…[25,26] Thisp henomenon certainly explainst he differences in the morphology and crystallinity observed upon changes in deposition conditions (spin coating solvent, speed and acceleration) in earlier studies. [22,45] Subsequent to the deposition,the optimisation of the SVAtime, which allows crystallites to grow to ad etermineds ize, establishes at rade off between high hole mobility and ah igh D-A interface. Importantly,t he SVA, thickness andD /A ratio are relatedi ndirectly as changes in the D/A ratio will impact the energetics of crystallite growth, which in turn will impose al imitation on the maximum attainable thickness, itself determined by the maximum attainablehole mobility in ag iven crystalline state.…”

“…[22] The powdered active layer methodc onsists of the deposition of activel ayers on large-area glass substrates, annealing them for an extended period of time to promote crystalline growth and recording ap owder diffractogram (transmission Bragg-Brentano geometry) of the solidt hat results from scrapping off the film, hence ap owdered film. Although the above morphological features are important to understand the formation of the D-A interface andc harget ransport, the actual arrangement of the donor molecules in the crystallite is determinant to enhancet he hole mobility.T he characterisationo fs uch an arrangement (the crystalline phase in whicht he donor packs) has been performed rarely because of the limitation imposed by the nanoscopics cale of the crystallites.…”

“…It relies on the comparison of diffractograms of "powdered" active layers with single-crystal structures obtained from their respective donor. [22] The powdered active layer methodc onsists of the deposition of activel ayers on large-area glass substrates, annealing them for an extended period of time to promote crystalline growth and recording ap owder diffractogram (transmission Bragg-Brentano geometry) of the solidt hat results from scrapping off the film, hence ap owdered film. This allowsu st od etermine the crystalline phase in which the donors are packed in thin films accurately because of the highera mount of peaks present in the diffractogram with respect to that if ad iffractogram is recordedd irectly from the film on the substrate.…”

Photoluminescence of Squaraine Thin Films: Spatial Homogeneity and Temperature Dependence

“…The squaraines used here, referred to as SQIB thereafter, are terminated by isobutyl chains, being added to steer molecular packing in the solid state. Two crystal structures are known for SQIB, a monoclinic polymorph in which the molecules adopt a classical herringbone packing and an orthorhombic structure with molecules arranged in a cofacial herringbone motif (Figure b,c) . With increasing temperature, the monoclinic polymorph changes to the orthorhombic one, although both structures coexist in a wide temperature range.…”