Solar energy is undoubtedly one of the most exploitable energy sources providing a potential solution to address the environmental issues deriving from the excessive use of fossil fuels. Over the last few years p-type dye sensitized solar cells (p-DSCs) have attracted substantial attention, since their incorporation with n-type DSCs could potentially lead to more efficient tandem cell pn-DSCs. Moreover, new research has been devoted to dye-sensitized photoelectrochemical cells (DSPECs), in which solar energy is utilized to generate hydrogen via water splitting. This article provides a summary of recent sensitizers employed in dye-sensitized NiO photocathodes for DSC and DSPEC, discussing approaches to enhance their overall performance. In particular, we intend to provide new directions through molecular design of new dyes and stimulate additional research development in the fields of DSCs and DSPECs.

The syntheses, as well as the photophysical and electrochemical characterization, of two novel BODIPY–porphyrin dyads and their first application in lighting schemes are provided. The benefits ascribed to their unique features, namely (i) a good electronic alignment, (ii) a remarkable efficient energy transfer, and (iii) excellent film morphology, lead to deep-red lighting devices with stabilities of around 1000 h and efficiencies of 0.13 Lm W⁻¹.

Copper-based tandem schemes have emerged as promising strategies to promote the formation of multi-carbon products in the electrocatalytic CO₂ reduction reaction. In such approaches, the CO-generating component of the tandem catalyst increases the local concentration of CO and thereby enhances the intrinsic carbon–carbon (C–C) coupling on copper. However, the optimal characteristics of the CO-generating catalyst for maximizing the C₂ production are currently unknown. In this work, we developed tunable tandem catalysts comprising iron porphyrin (Fe-Por), as the CO-generating component, and Cu nanocubes (Cucub) to understand how the turnover frequency for CO (TOF_CO) of the molecular catalysts impacts the C–C coupling on the Cu surface. First, we tuned the TOF_CO of the Fe-Por by varying the number of orbitals involved in the π-system. Then, we coupled these molecular catalysts with the Cu_cub and assessed the current densities and faradaic efficiencies. We discovered that all of the designed Fe-Por boost ethylene production. The most efficient Cu_cub/Fe-Por tandem catalyst was the one including the Fe-Por with the highest TOF_CO and exhibited a nearly 22-fold increase in the ethylene selectivity and 100 mV positive shift of the onset potential with respect to the pristine Cu_cub. These results reveal that coupling the TOF_CO tunability of molecular catalysts with copper nanocatalysts opens up new possibilities towards the development of Cu-based catalysts with enhanced selectivity for multi-carbon product generation at low overpotential.

A novel BODIPY-porphyrin triad PorCOOH-(BDP)₂ (scorpion shaped) was prepared, in which two BODIPY molecules are covalently attached via a 1,3,5-triazine molecule to a free-base carboxyphenyl meso-substituted porphyrin. The chromophore was synthesized via stepwise substitution reactions of cyanuric chloride. Photophysical and electrochemical studies of this triad, in combination with DFT theoretical calculations, suggest that there is negligible electronic interaction between the porphyrin and BODIPY moieties in the triad's ground states, but the frontier orbital energy levels are suitable for use as sensitizers in dye-sensitized solar cells (DSSCs). Solar cells sensitized by triad PorCOOH-(BDP)₂ were fabricated, and were found to exhibit a power conversion efficiency (PCE) value of 5.17% under illumination (AM1.5, 100 mW cm²) and with a TiO₂ film of 12 μm thickness, with a sensitization time of 3 h without any coadsorbent. The PCE value of DSSC was enhanced to 6.20% when a thin layer of reduced graphene oxide (rGO) was incorporated between TiO₂ and PorCOOH-(BDP)₂ dye, which is attributed to the formation of an rGO–TiO₂ Schottky barrier in the device, leading to efficient charge transport of injected electrons towards the external circuit, resulting in higher J_sc and FF. Electrochemical impedance spectra (EIS) demonstrate that a photoelectrode with rGO–TiO₂ exhibits shorter transport time of electrons, longer electron lifetime and lower charge transfer resistance.