Intragrain Heterostructure in 3D Perovskite: New Era of Bright PeLEDs with Low Efficiency Roll-Off

• • EQEs of PeLEDs have increased from <1% to over 30% (reference 1), but high EQEs are often at low brightness; this work addresses the efficiency roll-off at high current densities. • • The developed intragrain heterostructure in 3D CsPbI3−xBrx PeLEDs achieved ultrabright and highly efficient pure-red emission with extremely low efficiency roll-off, as reported in Nature (reference 8). • • Device-level electrically excited transient absorption (EETA) spectroscopy identified hole leakage into the PO-T2T hole-blocking layer as the cause of efficiency roll-off, evidenced by increasing EIA signals at ~420 and ~500 nm with bias. • • The molecule-in-lattice approach constructs wide bandgap barriers inside perovskite grains, reducing hole leakage while maintaining carrier transport, leading to suppressed efficiency roll-off at high brightness.