Special Section on “Next Generation Solar Cells”

Abstract

Molecular photovoltaic devices, in a broad sense, are devices made by using molecules or molecular materials that are capable of converting sunlight into electrical current and voltage. Since the use of low molecular weight organic molecules by Tang,[1] the sensitization of TiO2 with dyes coupled to the use of iodine/iodide red/ox couple by Grätzel and O'Regan,[2] the fabrication of bulk-heterojunction polymer/fullerene-based films by Sariciftci et al.,[3] to the latest breakthrough using hybrid lead based perovskite semiconductor materials by Miyasaka and collaborators,[4] there has been an amazing journey harnessing solar power. The dream for cheap, globally available solar energy is closer than ever with a great deal of excellent research being done in laboratories worldwide. This special collection of research articles in Solar RRL presents a flavor of the research done recently in hot research topics from dye sensitized solar cells, organic solar cells, and perovskite solar cells and serves as an example about how proactive the research in molecular photovoltaic devices is. Photochromic thin films based on Grätzel solar cells represent the ultimate frontier in the application of transparent devices that hold the promise for efficient translucid solar cells for applications in building photovoltaics. The dye design still holds the key for the optimization of the solar cell efficiency, when the primary role of the solar cell is not just the efficiency but also its transparency and its operational stability. In organic solar cells, the design of molecules and organic materials with alike goal, transparency, is also key. Moreover, taking into account the general low open circuit voltage in organic solar cells, it is also crucial to understand and reduce the possible pathways for voltage losses, which leads to better solar cell efficiencies. In fact, the efficiency of organic solar cells has exponentially increased during the last few years due to the synthesis and use of non-fullerene electron acceptor molecules and molecular materials. Further research on non-fullerene electron acceptors, as well as organic doping of semiconductors, will remain a hot topic in the near future with the challenge to match the current efficiency of their perovskite-based counterparts. Perovskite semiconductor materials for photovoltaic applications have been, without doubt, a major achievement in recent research. Applications ranging from energy conversion devices, artificial lighting, sensors and photonic applications, have rapidly appeared in the scientific literature since 2009. Indeed, scientific challenges remain, such as the passivation of defects to boost the solar cell efficiencies and the replacement of lead by a less harmful element, but the gap between laboratory and industrial deployment is closing rapidly. For their industrial application, better materials for grids, low-cost manufacture contacts, and treatments to increase the device stability are goals that will be the focus of present and future intense research. Emilio Palomares studied Biology at the UVEG. After graduating, he joined Prof. Hermenegildo García's group at the UPV where he got his PhD. In 2009, he was awarded an ERC Starting Grant to work on quantum dots for energy conversion devices and an ERC PoC in 2015. In 2019, he was awarded Energy & Environmental Solutions International Chair (E2S) by the Université de Pau et des Pays de l'Adour (UPPA). Later in 2020, he was elected ICIQ Director for the next 5 years. His research is focused on several aspects of light induced electron transfer reactions in supramolecular structures and nanostructured inorganic materials, which has evolved towards the control and improvement of the reactions that govern the efficiency on devices such as molecular solar cells, the creation of new hybrid nanomaterials for hydrogen production, and molecular based sensing devices to detect toxic substance in the environment. He is also involved in promoting science and education in society through chemistry workshops for primary and secondary schools.