Overcoming Outcoupling Limit in Perovskite Light-Emitting Diodes with Enhanced Photon Recycling.

Photon recycling (PR), reabsorption and reemission of photons, can randomize the propagation direction of photons trapped in the waveguide mode and potentially increase the outcoupling efficiency of perovskite light-emitting diodes (PeLEDs). However, the contribution of PR in PeLEDs has not been experimentally quantified in real device structures. Here, we show that, with the PR effect, the external quantum efficiency (EQE) of PeLEDs remains above 15% with extraordinary thick perovskite layers up to 2200 nm, which is much higher than the outcoupling efficiency (4.3%) of the thick emissive layer device with an emission zone near the TPBi layer without PR. We designed monolithic device structures to experimentally quantify the PR contribution under device working conditions and reveal that the PR can contribute 2.4%-40.4% of the total emission in PeLEDs depending on film thickness. This work provides an important way of manipulation and quantification of PR contribution in perovskite optoelectronic devices.