The Sun rises on perovskites

Since perovskite solar cells were first reported in 2009, their record efficiency has gone from 3.8% to over 25%. Scarcely a week passes without a breakthrough unveiled in stability, efficiency or applicability. The world is awash with perovskite start-ups and spin-outs from top universities. And yet if you try to buy solar cells for a rooftop or campervan, you will be offered only silicon or perhaps less efficient thin film alternatives. Now the commercial launch of perovskite solar cells is planned this year, and the question of whether they will bear the burden of expectation becomes ever more urgent.

Perovskites attract the photovoltaics community for many reasons. Perhaps most importantly, they are easily made by crystallisation from solution. This doesn’t produce defect-free films, but it doesn’t need to. Perovskites are also extremely attractive for ‘tandem’ solar cells, comprising sequential layers with different bandgaps to make more efficient use of broad-spectrum light. The main obstacles to perovskites’ commercialisation, however, have been instability issues.