2023 saw a series of major events: King Charles was crowned, three American banks collapsed, India surpassed China as the world’s most populous nation and Australia won the Cricket World Cup. One small piece of news, however, came to us in January 2024: 2023 was the hottest year ever recorded, since records began in 1850.
Climate change is no longer a distant future threat – in fact, we are already living in its midst. We as a planet have never had a stronger need for replacing our dependence on fossil fuels with cleaner sources of power. This is where innovation in photovoltaic renewable energy comes into play: the last few years have seen tremendous progress.
Quite likely, the biggest buzzwords you’ve heard are “perovskite” and “tandem cells”. A perovskite is simply a crystal structure, made of any material, that can be added to regular silicon based solar cells as a top layer. It helps absorb energy from different wavelengths of sunlight that the cell can’t absorb on its own – it works in tandem with the silicon, hence the name ‘tandem cell’. Under lab conditions, these tandem cells have shown gains of up to 33%. Most scientists working on tandem cells have projected at least a 20% gain in power delivery on a commercial scale. This means that an existing 1 GW silicon based photovoltaic power system could be upgraded to 1.2 GW simply by layering the panels with perovskite! The challenge that remains is to manufacture perovskites en masse that do not degrade with exposure to heat and moisture.
Another interesting trend we see in photovoltaic power systems is transparent solar. Organic salts inside a sheet of glass absorb ultraviolet light (not visible to the human eye) and allow the visible light spectrum to pass through, meaning that these sheets can be used to make windows that generate electricity while still letting in the usual amount of light. Currently, the efficiency of these glass sheets is only 10%, less than half of the 20-24% we see in silicon base cells. But if transparent solar is installed on a massive scale (think of every east & west facing window being replaced with this technology) it would play a major role in boosting the world’s photovoltaic renewable energy capacity. As of 2022, a Dutch company, Physee, said it was installing 15,000 such panels in office buildings across Europe.
Researchers around the world have also been looking into alternatives to silicon. Take a look at Gallium Arsenide (GaAs)- although it was first experimented upon in the 1960s, notably for a spacecraft that went to Venus, recent developments have led to efficiencies of around 29% on an ordinary single-junction cell and 33% on a multi-junction cell. In 2022, the German institute Fraunhofer ISE demonstrated 68.9% efficiency for a GaAs thin film cell exposed to a laser with a wavelength of 858 nm, which remains an unbroken record. But high costs have kept GaAs technology from becoming mainstream in the world of photovoltaic power systems.
Other scientists have also been looking at Cadmium Telluride (CdTe) and Copper Iridium Gallium Selenide (CIGS). CdTe is renowned for having the smallest carbon footprint of any existing solar technology; it currently accounts for 5% of global photovoltaic renewable energy production. Efficiency is on par with silicon at around 20-22%. The main problem holding back CdTe is the toxicity of cadmium – there is no easy way to dispose of it when the panel reaches the end of its life. Some cadmium is also wasted during production, which cannot be disposed of. As for CIGS, it is used mainly to make thin-film solar cells (flexible and as thin as a sheet of paper) but is not well adopted in mainstream solar due to its poor upscaling (not as efficient as silicon on a commercial scale). CIGS could be used in specialized applications such as the back of folding smartphones, curved glass, etc.
We can clearly see that solar power has immense potential to be the leader of all green technologies. Costs per kWh have dropped 90% since 2010 and could drop even further as factories expand their manufacturing capacity. Solar is currently the largest contributor to newly installed renewable energy in India, China and the US. Given the accelerated pace of innovation in just the last decade, we strongly believe that the future of this industry will glow brighter and brighter.
