We designed highly efficient porphyrin sensitizers with two phenyl groups at meso-positions of the macrocycle bearing two ortho-substituted long alkoxyl chains for dye-sensitized solar cells; the ortho-substituted devices exhibit significantly enhanced photovoltaic performances with the best porphyrin, LD14, showing J(SC) = 19.167 mA cm(-2), V(OC) = 0.736 V, FF = 0.711, and overall power conversion efficiency η = 10.17%.

To understand the effects of solvent-solute hydrogen bonding (SSHB) on the excited-state dynamics of two GFP-like chromophores, p-ABDI and p-CFABDI, we have determined the quantum yields for fluorescence (Φf) and the isomerization Z → E (ΦZE) and the femtosecond fluorescence and transient infrared absorption in selected solvents. The behavior that ΦZE ≅ 0.50 in aprotic solvents, such as CH3CN, indicates that the E-Z photoisomerization adopts a one-bond-flip mechanism through the torsion of the exocyclic C═C bond (the τ torsion) to form a perpendicular species (τ ∼90°) in the singlet excited state followed by internal conversion (IC) to the ground state and partition to form the E and Z isomers with equal probabilities. The observed ΦZE decreased from 0.50 to 0.15-0.28 when CH3CN was replaced with the protic solvents CH3OH and CF3CH2OH. In conjunction with the solvent-independent rapid (<1 ps) kinetics for the fluorescence decay and the solvent-dependent slow (7-20 ps) kinetics for the ground-state recovery, we conclude that the SSHB modifies the potential energy surface for the τ torsion in a way that the IC occurs also for the twisted intermediates with a τ-torsion angle smaller than 90°, which favors the formation of the Z isomers. The possibility of IC induced by torsion of the exocyclic C-C bond (the φ torsion) is also considered but excluded.

To rationalize the efficient quenching of the fluorescence and the Z → E photoisomerization of m-ABDI, the meta-amino analogue of the green fluorescent protein (GFP) chromophore, in protic solvents, the femtosecond time-resolved fluorescence and transient infrared (TRIR) spectra of m-ABDI in CD3CN, CH3OH, and CD3OD are determined. For solutions in CD3CN, the fluorescence decay lifetime is ∼7.9 ns and IR absorption lines near 1513, 1531, 1557, and 1613 cm(-1) of m-ABDI in its electronically excited state were observed with a decay time >5 ns. For solutions in CH3OH, the fluorescence decay is double exponential with time constants of ∼16 and 62 ps. In addition to IR absorption lines of m-ABDI in its electronically excited state with a decay time of ∼16 ps, new features near 1513, 1532, 1554, and 1592 cm(-1) were observed to have a rise time of ∼19 ps and a decay constant of ∼58 ps, indicating formation of an intermediate. The assignments for the IR spectra of the ground and excited states were assisted with DFT and TDDFT calculations, respectively. We conclude that the torsion of the exocyclic C═C bond (the τ torsion) is responsible for the nonradiative decay of electronically excited m-ABDI in CD3CN. However, in CH3OH and CD3OD, the solute-solvent hydrogen bonding (SSHB) interactions diminish significantly the barrier of the τ torsion and induce a new pathway that competes successfully with the τ torsion, consistent with the efficient fluorescence quenching and the diminished yield for Z → E photoisomerization. The new pathway is likely associated with excited-state proton transfer (ESPT) from the solvent to m-ABDI, particularly the carbonyl group, and generates an intermediate (ESPT*) that is weakly fluorescent.

We designed a dimeric porphyrin dye based on an efficient push–pull zinc porphyrin with extended π-conjugation so that the light-harvesting ability exhibits a panchromatic feature covering a broad spectral region from 400 nm to 900 nm.

The excitonic relaxation dynamics of perovskite adsorbed on mesoporous thin films of Al 2 O 3 and NiO upon excitation at 450 nm were investigated with femtosecond optical gating of photoluminescence (PL) via up-conversion. The temporal profiles of emission observed in spectral region 670-810 nm were described satisfactorily with a composite consecutive kinetic model and three transient components representing one hot and two cold excitonic relaxations. All observed relaxation dynamics depend on the emission wavelength, showing a systematic time-amplitude correlation for all three components. When the NiO film was employed, we observed an extent of relaxation proceeding through the nonemissive surface state larger than through the direct electronic relaxation channel, which quenches the PL intensity more effectively than on the Al 2 O 3 film. We conclude that perovskite is an effective hole carrier in a p-type electrode for NiO-based perovskite solar cells showing great performance.