Firms commercializing perovskite–silicon ‘tandem’ photovoltaics say that the panels will be more efficient and could lead to cheaper electricity.

On the outskirts of Brandenburg an der Havel, Germany, nestled among car dealerships and hardware shops, sits a two-storey factory stuffed with solar-power secrets. It’s here where a UK firm is producing commercial solar cells using perovskites: cheap, abundant photovoltaic (PV) materials that some have hailed as the future of green energy. Surrounded by unkempt grass and a weed-strewn car park, the factory is a modest cradle for such a potentially transformative technology, but the firm’s chief technology officer Chris Case is clearly in love with the place. The firm is one of more than a dozen companies betting that perovskites are finally poised to push the global transition to renewable energy into overdrive. A few niche perovskite-based PV products are already on the market, but announcements this year signal that many more are set to join them. 

Silicon is the workhorse material inside 95% of solar panels. Rather than replace it, Oxford PV, Qcells and others are piggybacking on it — layering perovskite on silicon to create so-called tandem cells. Because each material absorbs energy from different wavelengths of sunlight, tandems could potentially deliver at least 20% more power than a silicon cell alone; some scientists project much greater gains. Perovskite supporters say that this extra electricity could more than offset the additional costs of tandem cells, particularly in crowded urban areas or industrial sites where space is at a premium. 

As perovskite–silicon tandems get closer to market, excitement has boiled over into headlines predicting that a “revolutionary” “miracle material” is “about to change the world”. The reality is that the industry faces at least two major challenges in its battle to transform the solar market.

First, published research shows that the perovskites’ performance declines much more quickly than silicon when they are exposed to moisture, heat and even light. Oxford PV says it has done private research that’s overcome this issue. But “for commercial manufacturing, I would say stability is the key challenge that still remains”, says Fabian Fertig, Qcells’ director of research and development for wafers and cells, who leads the company’s development of perovskite–silicon tandems.

And second, some analysts see perovskites — at least in the short term — as largely irrelevant to the growth of solar power. Silicon modules have become incredibly cheap and efficient over the past decade, and companies in China continue to expand manufacturing capacity at a startling rate. In 2022, the world had about 1.2 terawatts (TW) of generating capacity from solar power, which in turn provided around 5% of global electricity generation. Energy strategists suggest that the world will need 75 TW by 2050 to meet climate goals. This requires installations to rise above 3 TW per year by the mid-20301, but the silicon PV industry is projected to achieve that, making it one of the rare green-technology areas that is on track (see ‘Solar’s expansion plans’).