Christian Kloc

The ultrafast dynamics of triplet excitons and polarons in hexaphenyl film was investigated by time-resolved fluorescence and femtosecond transient absorption techniques under various excitation photon energies. Two distinct pathways of triplet formation were clearly observed. Long-lived triplet states are populated within 4.5 ps via singlet fission-intersystem crossing, while the short-lived triplet states (1.5 ns) are generated via singlet fission from vibrational electronic states. In the meantime, polarons were formed from hot excitons on a timescale of <30 fs and recombined in ultrafast lifetime (0.37 ps). In addition, the characterization of hexaphenyl film suggests the morphologies of crystal and aggregate to wide applications in organic electronic devices. The present study provides a universally applicable film fabrication in hexaphenyl system towards future singlet fission-based solar cells.

Weak intermolecular interactions in organic semiconducting molecular crystals play an important role in determining molecular packing and electronic properties. Single crystals of metal‐free and metal phthalocyanines were synthesized to investigate how the coordination of the central metal atom affects their molecular packing and resultant electronic properties. Single‐crystal field‐effect transistors were made and showed a hole mobility order of ZnPc>MnPc>FePc>CoPc>CuPc>H₂Pc>NiPc. Density functional theory (DFT) and 1D polaron transport theory reach a good agreement in reproducing the experimentally measured trend for hole mobility. Additional detail analysis at the DFT level suggests the metal atom coordination into H₂Pc planes can tune the hole mobility via adjusting the intermolecular distances along the shortest axis with closest parallel π stackings.

Weak intermolecular interactions in organic semiconducting molecular crystals play an important role in determining molecular packing and electronic properties. Single crystals of metal‐free and metal phthalocyanines were synthesized to investigate how the coordination of the central metal atom affects their molecular packing and resultant electronic properties. Single‐crystal field‐effect transistors were made and showed a hole mobility order of ZnPc>MnPc>FePc>CoPc>CuPc>H₂Pc>NiPc. Density functional theory (DFT) and 1D polaron transport theory reach a good agreement in reproducing the experimentally measured trend for hole mobility. Additional detail analysis at the DFT level suggests the metal atom coordination into H₂Pc planes can tune the hole mobility via adjusting the intermolecular distances along the shortest axis with closest parallel π stackings.

Weak intermolecular interaction in organic semiconducting molecular crystals plays an important role in molecular packing and electronic properties. Here, four five‐ring‐fused isomers were rationally designed and synthesized to investigate the isomeric influence of linear and angular shapes in affecting their molecular packing and resultant electronic properties. Single‐crystal field‐effect transistors showed mobility order of 5,7‐ICZ (3.61 cm² V⁻¹ s⁻¹) >5,11‐ICZ (0.55 cm² V⁻¹ s⁻¹) >11,12‐ICZ (ca. 10⁻⁵ cm² V⁻¹ s⁻¹) and 5,12‐ICZ (ca. 10⁻⁶ cm² V⁻¹ s⁻¹). Theoretical calculations based on density functional theory (DFT) and polaron transport model revealed that 5,7‐ICZ can reach higher mobilities than the others thanks to relatively higher hole transfer integral that links to stronger intermolecular interaction due to the presence of multiple NH⋅⋅⋅π and CH⋅⋅⋅π(py) interactions with energy close to common NH⋅⋅⋅N hydrogen bonds, as well as overall lower hole‐vibrational coupling owing to the absence of coupling of holes to low frequency modes due to better π conjugation.

Weak intermolecular interaction in organic semiconducting molecular crystals plays an important role in molecular packing and electronic properties. Here, four five‐ring‐fused isomers were rationally designed and synthesized to investigate the isomeric influence of linear and angular shapes in affecting their molecular packing and resultant electronic properties. Single‐crystal field‐effect transistors showed mobility order of 5,7‐ICZ (3.61 cm² V⁻¹ s⁻¹) >5,11‐ICZ (0.55 cm² V⁻¹ s⁻¹) >11,12‐ICZ (ca. 10⁻⁵ cm² V⁻¹ s⁻¹) and 5,12‐ICZ (ca. 10⁻⁶ cm² V⁻¹ s⁻¹). Theoretical calculations based on density functional theory (DFT) and polaron transport model revealed that 5,7‐ICZ can reach higher mobilities than the others thanks to relatively higher hole transfer integral that links to stronger intermolecular interaction due to the presence of multiple NH⋅⋅⋅π and CH⋅⋅⋅π(py) interactions with energy close to common NH⋅⋅⋅N hydrogen bonds, as well as overall lower hole‐vibrational coupling owing to the absence of coupling of holes to low frequency modes due to better π conjugation.

We report the synthesis of TiS ₂ by chemical vapour transport and evaluated as insertion host for Na‐ion battery. The half‐cell assemblies are fabricated to study the Na‐insertion properties. The Na/TiS ₂ cell displayed a reversible capacity of ∼146 mAh g ^–1 at 0.1 C rate which corresponds to ∼0.61 mol. Na. Excellent cycling stability, and rate performance are noted for TiS ₂ . Cyclic voltammetry and impedance measurements supports the charge storage mechanism and interfacial properties, respectively. Operando studies are also conducted to ensure the structural stability of the insertion host. Furthermore, the Li‐insertion properties are also conducted to support the electrochemical activity of the host matrix prepared by chemical vapour transport.

7,7,8,8-Tetracyanoquinodimethane (TCNQ) and F_xTCNQ (x = 1, 2, 4) as acceptors and aromatic hydrocarbons form a variety of compounds in which the degree of charge transfer is tuned by crystal engineering.

A remarkable improvement in energy density was found using Se-substituted two-dimensional TiS₂ (TiSe_0.6S_1.4) as the insertion matrix in a Li-ion capacitor (LIC) assembly with activated carbon (AC) as the counter electrode.