Solar energy conversion via photoelectrochemical (PEC) cells offers a promising solution to current energy challenges, but significant advancements in materials and cell configurations are necessary. Until now, inorganic semiconductors such as metal oxides have been widely studied due to their affordability, non-toxicity and high stability. However, challenges such as charge recombination, low electron mobility and in some cases limited visible absorption limit their ability to obtain high conversion efficiencies. There are several strategies to improve the performance of photoelectrodes, ranging from the modification of materials to the incorporation of more systems that favor the reaction. In our group we are tackling several of them, such as the modification of electrode surfaces for optoelectronic modification, the incorporation of cocatalysts and, as a more innovative part, the use of organic semiconductors to prepare hybrid electrodes. Organic polymers, particularly conjugated polymers (CPs), show potential due to their light-harvesting and conductive properties. In particular, conjugated porous polymers (CPPs), with their 3D structure, provide improved stability and higher surface area. The combination of CPPs with widely studied materials like TiO₂ that suffer from limited visible light absorption due to their high bandgap energy can enhance the general performance.

In this talk, I will present to the audience different strategies to use CPP as multifunctional layers in photoelectrodes, which has been a challenge due to the normally used methodology to obtain these materials, generally composed of micron-sized particles. In this sense, our group has made an effort to design and develop several routes for the use of these materials in photoelectrochemical systems, in particular nanostructuring and electropolymerisation. In fact, these polymers have proven to be efficient as multifunctional layers since they have light absorption properties while they are good conductors of holes in the case of p and electrons in the case of n. We have been able to observe improved photocurrents and photopotentials in these hybrid electrodes. Furthermore, advanced characterizations have been carried out using electrochemical impedance spectroscopy and transient absorption spectroscopy and it has been shown that in most cases, when well designed, these heterojunctions can promote better charge transfer and longer lifetimes of the photogenerated charges. This finding opens the door to the use of these systems not only in photoelectrochemical devices but in any optoelectronic device where the preparation of quality thin films is of vital importance.