Perovskite-organic tandem solar cells with indium oxide interconnect.

Multijunction solar cells can overcome the fundamental efficiency limits of single-junction devices. The bandgap tunability of metal halide perovskite solar cells renders them attractive for multijunction architectures 1 . Combinations with silicon and copper indium gallium selenide (CIGS), as well as all-perovskite tandem cells, have been reported 2-5 . Meanwhile, narrow-gap non-fullerene acceptors have unlocked skyrocketing efficiencies for organic solar cells 6,7 . Organic and perovskite semiconductors are an attractive combination, sharing similar processing technologies. Currently, perovskite-organic tandems show subpar efficiencies and are limited by the low open-circuit voltage (V oc ) of wide-gap perovskite cells 8 and losses introduced by the interconnect between the subcells 9,10 . Here we demonstrate perovskite-organic tandem cells with an efficiency of 24.0 per cent (certified 23.1 per cent) and a high V oc of 2.15 volts. Optimized charge extraction layers afford perovskite subcells with an outstanding combination of high V oc and fill factor. The organic subcells provide a high external quantum efficiency in the near-infrared and, in contrast to paradigmatic concerns about limited photostability of non-fullerene cells 11 , show an outstanding operational stability if excitons are predominantly generated on the non-fullerene acceptor, which is the case in our tandems. The subcells are connected by an ultrathin (approximately 1.5 nanometres) metal-like indium oxide layer with unprecedented low optical/electrical losses. This work sets a milestone for perovskite-organic tandems, which outperform the best p-i-n perovskite single junctions 12 and are on a par with perovskite-CIGS and all-perovskite multijunctions 13 .