The Sun emits enough power onto Earth each second to satisfy the entire human energy demand for over two hours. Given that it is readily available and renewable, solar power is an attractive source of energy. However, as of 2024, less than two percent of the world’s energy came from solar. Historically, solar energy harvesting has been expensive and relatively inefficient. Even this meager solar usage, though, is an improvement over the previous two decades, as the amount of power collected from solar energy worldwide increased over 300-fold from 2000 to 2019. New technological advances over the last twenty years have driven this increased reliance on solar by decreasing costs, and new technological developments promise to augment this solar usage by further decreasing costs and increasing solar panel efficiency.

The utilisation of renewable energy as a future energy resource is drawing significant attention worldwide. The contribution of solar energy (including concentrating solar power (CSP) and solar photovoltaic (PV) power) to global electricity production, as one form of renewable energy sources, is generally still low, at 3.6%.

However, it has firmly established itself among other renewable energy technologies, comprising nearly 31% of the total installed renewable energy capacity in 2022, making it the second most installed renewable energy resource behind hydropower energy. The present review study, through a detailed and systematic literature survey, summarises the world solar energy status along with the published solar energy potential assessment articles for 235 countries and territories as the first step toward developing solar energy in these regions.

A comparison of the solar power status among countries and territories has been provided, considering their concentrated solar power and PV installed capacities for each continent. Although there has been a significant increase of approximately 22% in global solar energy installed capacity between 2021 and 2022, the literature survey reveals that clear gaps still exist in the field of solar energy. In the next three decades, the solar PV field can advance to become the second prominent generation source by constructing more solar farms, allowing countries to generate approximately 25% of the world's total electricity needs by 2050.

To outpace current solar cells, a new design would need to be able to capture more light, transform light energy to electricity more efficiently, and/or be less expensive to build than current designs. Energy producers and consumers are more likely to adopt solar power if the energy it produces is equally or less expensive than other, often non-renewable, forms of electricity, so any improvement to current solar cell designs must bring down overall costs to become widely used.

The first option, adding hardware that allows the solar cells to capture more light, does not actually require that we abandon current solar cell designs. Electronics can be installed with the solar cell that let the cell track the sun as it moves through the daytime sky. If the solar cell is always pointing at the sun, it will be hit by many more photons than if it was only pointing towards the sun around midday. Currently, designing electronics that can track the position of the sun accurately and consistently for several decades at a reasonable cost is an ongoing challenge, but innovation on this front continues. An alternative to making the solar cell itself move is to use mirrors to focus light on a smaller, and therefore cheaper solar cell.

Another route to improving the performance of solar cells is to target their efficiency so they are better at converting energy in sunlight to electricity. Solar cells with more than one layer of light-capturing material can capture more photons than solar cells with only a single layer. Recently, lab-tested solar cells with four layers can capture 46% of the incoming light energy that hit them. These cells are still mostly too expensive and difficult to make for commercial use, but ongoing research may one day make implementing these super-efficient cells possible.

The alternative to improving the efficiency of solar cells is simply decreasing their cost. Even though processing silicon has become cheaper over the past few decades, it still contributes significantly to the cost of solar cell installation. By using thinner solar cells, material costs decrease. These “thin-film solar cells” use a layer of material to harvest light energy that is only 2 to 8 micrometers thick, only about 1% of what is used to make a traditional solar cell. Much like cells with multiple layers, thin-film solar cells are a bit tricky to manufacture, which limits their application, but research is ongoing.

In the immediate future, silicon solar cells are likely to continue to decrease in cost and be installed in large numbers. In the United States, these cost decreases are anticipated to increase the solar power produced by at least 700% by 2050. Meanwhile, research on alternative designs for more efficient and less expensive solar cells will continue. Years from now, we are likely to see alternatives to silicon appearing on our solar farms and rooftops, helping to provide clean and renewable sources of energy. These improvements have and will continue to be made possible by increasing bulk manufacturing of solar cells and new technologies that make the cells cheaper and more efficient.