The future of solar energy: beyond silicon

BaZrS3 could revolutionize solar energy: non-toxic, stable and efficient, it promises to overcome the limits of silicon and halogenated perovskites

For decades, silicon has been the backbone of the photovoltaic industry, enabling the production of increasingly efficient solar cells. However, its theoretical efficiency limit, set at 29.4%, is rapidly approaching. To overcome this barrier, new materials and innovative approaches are required. This is where tandem solar cells come into play, designed to capture more energy by combining layers of different materials. The challenge is to find materials that complement silicon with efficiency and stability.

Halide perovskites: great potential and challenges

Over the past few years, halide perovskites have taken the solar technology world by storm. In the period from 2009 to 2021, their efficiency increased by 579%, while that of silicon increased by only about 57% during this period-a staggering achievement by comparison.

The strength of halide perovskites is that they can tolerate structural defects due to unique properties, including:

• Ferroelectricity: This enhances electron extraction and reduces energy loss.
• Rashba Effect: Extends the lifetime of electrons to maximum efficiency.
• Large Polarons: These shield electrons from internal defects.
• Hot Phonon Bottleneck: In solid-state physics, this phenomenon slows down the relaxation of high-energy phonons, which limits the dissipation of energy within the material. Energy loss is minimized to convert more light into electricity.

Notwithstanding such scientific wonders, halide perovskites have two major Achilles’ heels: they contain lead and are therefore toxic, and they readily degrade in the presence of heat, light, and humidity. This makes their large-scale commercial utilization very difficult.

BaZrS3: a sustainable future for solar power

Among these emerging solutions, BaZrS3, commonly known as a chalcogenide perovskite, has emerged as a hopeful substitute for halide perovskites. Non-toxic, stable, and with excellent optical properties, BZS seems to be a strong candidate for the next-generation solar cells.

For that, ACAP researchers used cutting-edge supercomputers to tune BZS properties by applying structural strain-something impossible to do with conventional materials-which allowed it to implement some of the amazing features of halide perovskites while retaining stability and environmental safety.

They laid down the ambitious plans: stacking 100 ultra-thin, semitransparent layers of BZS can eventually boost efficiencies of up to an unprecedented factor and, with silicon combinations, potentially yield efficiencies well in excess of a record-setting 38% at the silicon level. Communications Materials published this.

However, it is hard to produce by means of manufacturing because, being so stable, only very controlled environments would prevent it from contamination in processes, given the tendency of barium and zirconium to bond with oxygen, which seriously impairs the quality of the final product. Nevertheless, the mentioned difficulties cannot undermine its great prospects: if the BZS can only serve to raise solar cell efficiency, that will make this source of energy much more benign and ‘greener.’.

Source: Communications Materials