Progress on Nanomaterials for Photoelectrochemical Solar Cells: from Titania to Perovskites

Solar cells have been the queen of alternative renewable energy for the earth. From silicon-based solar cells to the new generation of perovskite-based solar cells, the choice and performance of the materials of the corresponding cells are still the focus of research interest. Amongst, photoelectrochemical (PEC) solar cells trigger the use and exploration of nanomaterials to boost their cell’s performance. This short review focus on the development of nanomaterials used for PEC, from nanoparticles to the one-dimensional titanium dioxide (titania) such as nanofibers and nanotubes, as well as the hybrid system with the perovskite halide. The search for light-harvesting materials is also included especially natural dyes. The review ends with a strategy to marry the natural dyes' potential with the sophisticated structure of nanomaterials to result in an efficient natural dyes PEC solar cells.

Review on the Materials Properties and Photoelctrochemical (PEC) Solar Cells of CdSe, Cd1-xZnxSe, Cd1-xInxSe, Thin Films

CdSe and its Zn/In/suitable element doped films are very important interesting materials for the realization of electronic and photoelectronic devices for energy conversion. The growth of ternary In/Zn/Cd selenides opens up the possibility of their applications for novel opto-electronic devices in the visible region of electromagnetic radiation. The (CdZn)Se and (CdIn)Se systems enable a tunable band gap region between 1.72 and 2.82 eV at normal temperature facilitating the development of several new light emitting diodes, photo detectors, blue green lasers. Thin films of these materials are usually synthesized by molecular beam epitaxy, electron beam evaporation and chemical techniques. Many researchers have reported about these materials prepared by different techniques and their properties as well as their use in PEC cell fabrication mainly followed by other optoelectronic devices also. This review gives an account of all these data in a representative distributed manner so as to cover many decades of published papers in this ever green topic of energy conversion research.

Studies on the Influence of In and Zn Doping on the CdSe Based Photo Electro Chemical (PEC) Solar Cells Using Electron Beam Evaporation Technique

CdSe thin films doped with 10% of Indium and 10 % Zinc were prepared by electron beam evaporation technique and the films were annealed at 200 oC for 30 min. Well crystalline films were deposited and the crystallite variation was studied for doping effect and it was found to be about 48 and 52 nm respectively. Optical band gap values are found to be modified by doping as well as annealing. PEC solar cells were fabricated using CdSe:In and CdSe:Zn films which showed 1.54% and 1.88% conversion efficiency respectively. Annealed films showed considerable influence in the optoelctronic properties and its improvement in conversion efficiency to about 2.75% and 2.87% respectively. In order to increase the photo output the films were annealed at 200o C at temperature. The photo output was Voc = 0.476 V, Jsc = 9.8 mA cm-2, ff = 0.44, η = 2.76 % at 80 mW cm-2. Photoetching increased the output parameters.

Electrocatalytic conversion of CO2 to produce solar fuels in electrolyte or electrolyte-less configurations of PEC cells

The electrocatalytic reduction of CO2 is studied on a series of electrodes (based on Cu, Co, Fe and Pt metal nanoparticles deposited on carbon nanotubes or carbon black and then placed at the interface between a Nafion membrane and a gas-diffusion-layer electrode) on two types of cells: one operating in the presence of a liquid bulk electrolyte and the other in the absence of the electrolyte (electrolyte-less conditions). The results evidence how the latter conditions allow productivity of about one order of magnitude higher and how to change the type of products formed. Under electrolyte-less conditions, the formation of >C2 products such as acetone and isopropanol is observed, but not in liquid-phase cell operations on the same electrodes. The relative order of productivity in CO2 electrocatalytic reduction in the series of electrodes investigated is also different between the two types of cells. The implications of these results in terms of possible differences in the reaction mechanism are commented on, as well as in terms of the design of photoelectrocatalytic (PEC) solar cells.