Current and upcoming innovations in solar cell technologies
Solar energy, the third-largest renewable energy source after hydropower and wind, has emerged as a clean, sustainable, and powerful alternative to fossil fuels. The sunlight striking the Earth is more than 10,000 times the world’s total energy use, and technologies to harvest as much solar energy as possible are surging rapidly. Since the first commercial silicon (Si) solar panels created by Bell Laboratories in 1954, the most common technologies today use different forms of Si-based solar cells and convert up to 20% of the sunlight to electricity.
According to IEA’s market analysis, the generation of solar photovoltaics (PV) — the process of converting sunlight into electricity — has reached 720 TWh in 2019 from 585 TWh in 2018 and is expected to grow up to 1,940 TWh by 2025. The current maximum global capacity of solar energy is 592 GW, contributing 2.2% to global electricity generation.
What are the current and upcoming innovative materials?
A typical solar cell consists of semiconducting materials such as p- and n-type silicon with a layered p-n junction connected to an external circuit. Sunlight illumination on the panels causes electron ejection from silicon. The ejected electrons under an internal electric field create a flow through the p-n junction and the external circuit, resulting in a current (electricity). With a swiftly growing market and the development of creative applications, R&D on innovative solar energy materials is at its peak to achieve maximum solar-to-electricity efficiency at low cost. Three types of highly investigated semiconducting materials of today are crystalline Si, thin films, and the next-generation perovskite solar cells (PSCs).
Crystalline silicon (c-Si) is the most used semiconducting material in solar panels, occupying more than 90% of the global PV market, although the efficiency is significantly under the theoretical limit (~30%). Solar cells made of alternative low-cost and high-efficiency materials are emerging.
The National Renewable Energy Laboratory (NREL) is driving the development of high-efficiency crystalline PVs, which includes III-V multijunction materials (with target efficiency of >30%) and hybrid tandem III-V/Si solar cells. Their six-junction III-V solar cells have reached an efficiency of 47.1% under concentrated light. Moreover, Si-based bifacial technology can harvest solar energy from both sides of the panel, with 11% more efficiency compared to standard panels.