Tandem light-emitting diodes (LEDs), achieved by vertically stacking several units in series to combine the luminance of individual light-emitting elements, are effective for improving efficiency and lifespan compared with single-unit devices1–3. In particular, tandem perovskite LEDs benefit from the small Stokes shift of perovskites4, which—in principle—can enable substantial photon recycling between individual perovskite layers and enhance light extraction from trapped modes. However, a tandem structure that effectively merges the luminance of each perovskite unit still remains a notable challenge. Here we demonstrate efficient and stable tandem LEDs by combining two solution-processed perovskite light-emitting units. This tandem structure effectively combines the original luminance of each light-emitting unit; we argue that the emissions are also substantially enhanced through photon recycling between the individual light-emitting units. Consequently, we achieve tandem perovskite LEDs with a low turn-on voltage of 3.2 V, a high peak external quantum efficiency (EQE) of 45.5% (even 20% higher than the sum of the peak EQEs of single-unit devices), an average peak EQE of 40.9% and a half-lifetime of 64 h at an initial radiance of 70 W sr−1 m−2. These findings represent a notable advancement in achieving high-performance and multicolour LEDs through the stacking of perovskite LEDs.
