Efficient near-infrared harvesting in perovskite–organic tandem solar cells

Abstract

The broad bandgap tunability of both perovskites and organic semiconductors enables the development of perovskite–organic tandem solar cells with promising theoretical efficiency. However, the certified efficiencies of reported perovskite–organic tandem solar cells remain lower than those of single-junction perovskite solar cells, primarily because of insufficient near-infrared photocurrent in narrow-bandgap organic subcells1, 2–3. Here we design and synthesize an asymmetric non-fullerene acceptor (NFA), P2EH-1V, featuring a unilateral conjugated π-bridge to reduce the optical bandgap to 1.27 eV while maintaining ideal exciton dissociation and nanomorphology. Transient absorption spectroscopy confirms efficient hole transfer from P2EH-1V to the donor PM6. Devices based on P2EH-1V exhibit reduced non-radiative voltage losses of 0.20 eV without compromising charge-generation efficiency. We achieve a 17.9% efficiency for the organic bottom cell, with a high short-circuit current density (Jsc) of 28.60 mA cm−2. Furthermore, we minimize interface recombination losses, enabling the perovskite top cell to achieve an impressive open-circuit voltage (Voc) of 1.37 V and a fill factor (FF) of 85.5%. These advancements result in perovskite–organic tandem solar cells achieving a record efficiency of 26.7% (certified at 26.4%) over an aperture area greater than 1 cm2.