Jafar Iqbal Khan

End‐group fluorination of the well‐known non‐fullerene acceptor (NFA) ITIC extends the absorption spectrum to the near‐infrared (NIR), increasing the solar cells’ photocurrent compared to the non‐fluorinated version. Here, ITIC and its fluorinated variants (asymmetric ITIC‐2F ^* and symmetric ITIC‐4F) were synthesized, and the effect of fluorination on physicochemical, optical, electronic, and photovoltaic properties was systematically investigated. Fluorination increases the acceptors’ electron affinity (EA), consequently reducing the device photovoltage. The NFA's molecular quadrupole moment (QM) increases with the degree of fluorination, which improves exciton dissociation and reduces charge recombination at the donor‐acceptor (D‐A) interface. Simultaneously, the NFA ionization energy (IE) increases, facilitating hole transfer to the donor. Both effects improve the internal quantum efficiency (IQE) of solar cells upon NFA fluorination. Donor fluorination increases the donor's IE, potentially hampering hole transfer. Unfortunately, cyclic voltammetry (CV) recordings of single materials fail to accurately describe the energetic conditions at D‐A heterojunctions. Here, the unique capability of energy‐resolved electrochemical impedance spectroscopy (ER‐EIS) to detect the density of states (DOS) shows that the donor's IE is lower in blends than in the pristine material, thereby enabling hole transfer. In combination with the increased NFAs EA, enhanced charge generation quantum yields are obtained; however, ultimately, a trade‐off exists between photocurrent and photovoltage.

Partial quantum confinement effects can induce transient polarons localization which may mitigate the energy losses and charge carriers recombination in organic solar cells.

Y-family acceptors (A) have enabled organic solar cell efficiencies above 21%, yet the origin of their outstanding performance remains unresolved. To identify the governing factors, we compare two Y-derivative acceptors, Y6 and ZY-4Cl, across binary blends with 11 different electron donors (D). We show that hole transfer (HT) at the D–A interface is the efficiency-limiting step, requiring an ionization energy offset of only ~0.3 eV for Y6 compared to ~0.6 eV for ZY-4Cl, set by interface energetics rather than π-stacking differences. Extending to an even wider range of systems, we find that external quantum efficiency universally scales with the Gibbs free energy for charge transfer, collapsing onto distinct trends defined by the strength of the acceptor’s electron deficient end group. Stronger acceptor units yield a steeper efficiency rise, enabling high external quantum efficiencies at minimal energetic cost, largely independent of molecular family and challenging the perceived advantage of Y-derivatives.

Herein, we report the synthesis of six CF 3 -pyridyl-substituted aromatics via Suzuki-Miyaura cross-coupling, incorporating electronically diverse heterocyclic (pyrazine, benzothiadiazole) and homocyclic (chrysene, anthracene, pyrene, perylene) cores to systematically probe structure-property relationships. UV-Vis absorption, steady-state and time-resolved photoluminescence, electrochemical measurements, and quantum chemical calculations demonstrate that the homocyclic derivatives exhibit long fluorescence lifetimes (τ), high photoluminescence quantum yields (ɸ PL ), large dipole moment changes (Δμ), optimally aligned frontier energy levels, and backbone-delocalized charge redistribution. Among these, anthracene-based compound (H-An) shows longest τ and highest ɸ PL with strongly suppressed non-radiative decay, pyrene derivative (H-Py) displays the largest Δμ, while the perylene analogue (H-Per) demonstrate red-shifted absorption, computed high light-harvesting efficiency, minimal exciton binding energy, and the lowest hole and electron reorganization energies, highlighting their potential as bright emitter or absorber for optoelectronic applications. In contrast, the heterocyclic compounds (H-Pz and H-BTD) are weakly emissive or nearly non-emissive, indicative of dominant non-radiative relaxation pathways. Density functional and time-dependent DFT calculations reproduce the experimental trends, underscoring that strategic core engineering within the CF 3 -pyridyl framework is an effective approach for tuning optical, charge-transport, and emissive properties in organic optoelectronic materials.

The bi-molecular recombination rate ( γ ) of charge carriers in P3HT:NFA blends decreases gradually as the diagonal bandgap (IE _D –EA _A ) increases.

In recent years, the catalytic activity of scandium triflate Sc(OTf)₃ has attracted significant attention due to its robust Lewis acidity and the oxophilicity of Sc³⁺. These features have led to impressive progress in developing diverse organic reactions, including C-C bond formation. The Sc³⁺ also facilitates single electron transfer in photoinduced reactions either by coordination to an organophotoredox catalyst, which modifies its redox reactivity, or by the formation of a scandium–superoxide anion complex after electron transfer from a light-absorbing redox-active compound. The prior consideration of Sc³⁺ as a redox-inactive/innocent metal ion initially hampered the investigation of the possibility of using Sc(OTf)₃ as a sole visible light photoredox catalyst. This work demonstrates the use of Sc(OTf)₃ as a visible light photocatalyst capable of direct and mild aerobic oxidative C-H functionalisation of aromatic substrates by oxidation of the benzylic position and direct cyanation of the aromatic ring.

Thermally induced degradation of organic photovoltaic devices hinders the commercialization of this emerging PV technology. Thus, a precise understanding of the origin of thermal device instability, as well as identifying strategies to circumvent degradation is of utmost importance. Here, it investigates thermally‐induced degradation of state‐of‐the‐art PBDB‐T‐2F (PM6):BTP (Y6) bulk heterojunction solar cells at different temperatures and reveal changes of their optical properties, photophysics, and morphology. The open‐circuit voltage and fill factor of thermally degraded devices are limited by dissociation and charge collection efficiency differences, while the short‐circuit current density is only slightly affected. Energy‐resolved electrochemical impedance spectroscopy measurements reveal that thermally degraded samples exhibit a higher energy barrier for the charge‐transfer state to charge‐separated state conversion. Furthermore, the field dependence of charge generation, recombination, and extraction are studied by time‐delayed collection field and transient photocurrent and photovoltage experiments, indicating significant bimolecular recombination limits device performance. Finally, coupled optical‐electrical device simulations are conducted to fit the devices’ current‐voltage characteristics, enabling us to find useful correlations between optical and electrical properties of the active layers and device performance parameters.