Amjad Ali

Crystallographic orientation and lattice strain directly govern performance and stability; however, they are often treated as independent structural parameters, and therefore their combined influence on non‐radiative recombination remains poorly understood. Here, we reveal the interplay between these parameters and establish their correlation with non‐radiative recombination in perovskite solar cells (PSCs). The coupled control of structural parameters is achieved through novel bimolecular cooperative interactions between sodium hydroxyquinoline sulfonate and sodium aminonaphthalene sulfonate. These interactions regulate crystallization at molecular level by destabilizing solvent–PbI ₂ adducts. As a result, they promote out‐of‐plane growth of corner‐sharing [PbI ₆ ] ^4─ networks along [100] direction and shift the lattice strain from a tensile to a compressive state. This leads to an open‐circuit voltage of 1.22 V (only 49 mV behind the theoretical limit), achieving a power conversion efficiency (PCE) up to 26.21% and a reverse‐bias breakdown voltage of −16.5 V in PSCs. Furthermore, the device retains 90% of its initial PCE after 3300 h at >85% relative humidity. Control experiments further confirm that this integrated structural tuning is the dominant factor governing suppressed non‐radiative recombination and enhanced breakdown voltage.

A new family of symmetrical fluorene derivatives with different types of substituents attached to the C-2 and C-7 positions of the fluorene core synthesized by the Sonogashira coupling reactions is reported. The electronic structures and the properties of the compounds investigated by means of photoelectron emission spectroscopy, UV–Vis absorption and photoluminescent spectroscopy as well as by DFT and TD-DFT theoretical calculations are discussed. It is shown that the nature of substituents influences the π-conjugation of the molecules. No intermolecular charge transfer within the investigated wavelength range is observed. The applicability of the synthesized compounds in organic light-emitting diodes (OLEDs) based on exciplex emission is demonstrated. The advanced co-deposition technique with the tuned OLED architecture was applied and resulted in improved OLED parameters.

The acceptor–donor–acceptor structured fused-ring electron acceptors (FREAs) have piqued interest for organic solar cells. We herein employ time-dependent density functional theory to evaluate the effect of Hartree–Fock exact exchange (HFX) on the performance of 16 global hybrid functionals for computing the maximum absorption wavelengths (λ_ver-theo) and the vertical excitation energies (E_ver-theo) of 34 molecules. We customize the HFX ratio in the functionals used to perform an in-depth analysis of its impact on the E_ver-theo values. The computed λ_ver-theo values strictly follow an inverse proportionality to the HFX percentage. The performance of the methods with the same ratio of HFX is almost identical, such as B3LYP, B3PW91, and mPW3PBE containing 20% HFX. The performance enhances with a relatively higher HFX ratio of 21% in X3LYP, B971, B972, and 22% in B98 giving smaller deviations. APF and APFD containing 23% HFX provide the smallest deviations for all compounds, with a mean signed error limited to 0.02 eV and a mean absolute error (MAE) of 0.06 eV. The performance drops using M06 and M05 with comparatively higher HFX ratios providing MAE values of 0.07 eV and 0.1 eV, respectively. M06-2X with 54% HFX provides the largest MAE value of 0.35 eV. The lowest obtained MAE is 0.06 eV at 23 to 25% HFX in most of the functionals considered in this study, suggesting that these are the optimal values for the prediction of excitation energies of FREAs. It has also been found that global hybrids seem to be more efficient for larger-sized molecules with a smaller bandgap.