Recent Trends in Sustainable Solar Energy Conversion Technologies: Mechanisms, Prospects, and Challenges

The current global transition from conventional fossil-fuel-based systems to green, sustainable, and renewable energy is realizing new challenges associated with device efficiencies. Among the green energy approaches available, efficient solar energy conversion into green chemical and electrical energy can ensure the upcoming demands of global future energy in an environmentally friendly and sustainable way. However, the sunlight energy cannot be utilized directly as a result of its intermittent and diffuse nature. This demands the development of efficient and economically viable technologies for its efficient conversion to an applicable source of energy. The practical realization of this dream on an industrial scale is still a longstanding challenge for researchers. Therefore, the scientists and technologists across the globe are in constant pursuit to develop/improve highly efficient, environmentally benign, and economically viable sustainable chemistry and engineering devices. At present, three technologies: (i) photoelectrochemical water splitting, (ii) photoreforming of plastic- or biomass-derived waste, and (iii) organic photovoltaics in the form of perovskite solar cells have emerged as the best for converting the sunlight energy into organic valuables and "green" H2 fuel or electricity. In this review, we will focus on introducing the basic principles, mechanistic insights, recent trends, and future prospects for solar to green energy using these technologies.