The Importance of Exploring and Developing a Wide Variety of Photovoltaic Technologies

According to the latest Copernicus report [1], 2024 is expected to be the warmest year on record and the first year with temperatures more than 1.5 °C above pre-industrial levels; however, this growth is concerningly in line with the temperatures recorded last year and in previous years [2]. Furthermore, in recent decades, the effects of climate change have become increasingly evident. The impact of global warming on ecosystems also affects the lives and livelihoods of millions of people worldwide, making natural disasters more frequent and powerful while also exacerbating existing social and economic inequalities. It is well known that the natural climate has oscillated between warm periods and ice ages for the past million years. This fluctuation is closely related to Milankovitch cycles. However, the scientific community agrees, based on numerous studies, data, and simulations, that the changes in global temperature during the twentieth century can only be explained if both natural and anthropogenic processes are considered [3]. In particular, global warming is associated with the increasing concentration of greenhouse gases in the atmosphere. The Earth’s temperature is determined by the energy balance between absorbed solar radiation and emitted infrared radiation, and greenhouse gases absorb infrared radiation from the Earth’s surface. Without them, the Earth’s temperature would be close to minus 20 °C, making life as we know it impossible. On the other hand, an increase in greenhouse gases in the atmosphere reduces the emission of infrared radiation, creating an imbalance that results in an increase in temperature [4]. Approximately three-quarters of emissions of these gases come from energy use and consumption [5]; this is why replacing conventional energy sources with clean, renewable energy technologies is paramount. Furthermore, energy demand is expected to rise exponentially in the coming years, making it increasingly necessary to resort to energy sources that, unlike fossil fuels, are not at risk of depletion [6]. Renewable energy sources, such as solar, wind, hydropower, ocean and geothermal energy, biomass, and biofuels, are inexhaustible and cleaner alternatives to fossil fuels. They can lower greenhouse gas emissions, diversify our energy options, and reduce our dependence on volatile fossil fuel prices. Exploiting all these sources and utilizing every possible technology to diversify energy production is essential. Many of these sources are not present everywhere, nor are they constant over time. On the other hand, each source can be efficient for energy production if utilized in the right location and for the most suitable application. Therefore, it is essential not to focus on just one alternative energy source; the combined development and use of multiple sources can solve this pressing issue. One of the technologies that harness renewable energy sources, specifically solar energy, is photovoltaic (PV) PV technologies have been classified, depending on their development over time, into first-, second-, third-, and fourth-generation devices: The first generation is based on monocrystalline and polycrystalline silicon and gallium arsenide. The second generation focuses on developing thin-film PV technologies, such as CdTe and CIGS. The third generation includes “emerging technologies”, characterized by low manufacturing costs, non-toxicity, and elemental abundance of their constituent, such as perovskites and organic cells, as well as multi-junction devices. The fourth generation refers to a new hybrid technology under development that uses nanoparticles or organic nanomaterials such as graphene, carbon nanotubes, and graphene derivatives. Subsequent generations have been developed, in some cases, to reduce production costs and, in others, to address new technological needs or applications, without replacing or interrupting research on earlier technologies. To date, the market is still dominated by panels from the first two generations: approximately 97% consist of monocrystalline silicon, with the remainder consisting of CdTe thin-film devices [7]. This does not mean that research on new materials is useless; rather, it is essential to differentiate technologies and develop them all to ensure the proper technology is available for each purpose. Research is now focused not only on the development of traditional photovoltaic panels but also on, for example, devices for powering the Internet of Things (IoT) [8], and cells integrated into construction elements, building materials (building-integrated photovoltaics, BIPV), or space applications. Therefore, it is essential to develop materials that enable the development of devices with diverse characteristics, such as semi-transparent or colored cells, materials that can be deposited into light and flexible substrates, devices in superstrate or substrate configurations, etc.