Stabilized Low-Dimensional Species for Deep-Blue Perovskite Light- Emitting Diodes with EQE Approaching 3.4%

Despite recent encouraging developments, achiev-ing efficient blue perovskite light-emitting diodes (PeLEDs) have been widely considered a critical challenge. The efficiency breakthrough only occurred in the sky-blue region, and the device performance of pure-blue and deep-blue PeLEDs lags far behind those of their sky-blue counterparts. To avoid the negative effects associated with dimensionality reduction and excess chloride typically needed to achieve deep-blue emission, here we demonstrate guanidine (GA+)-induced deep-blue (similar to 457 nm) perovskite emitters enabling spectrally stable PeLEDs with a record external quantum efficiency (EQE) over 3.41% through a combination of quasi-2D perovskites and halide engineering. Owing to the presence of GA+, even a small inclusion of chloride ions is sufficient for generating deep-blue electroluminescence (EL), in clear contrast to the previously reported deep-blue PeLEDs with significant chloride inclusion that negatively affects spectral stability. Based on the carrier dynamics analysis and theoretical calculation, GA+ is found to stabilize the low-dimensional species during annealing, retarding the cascade energy transfer and facilitating the deep-blue EL. Our findings open a potential third route to achieve deep-blue PeLEDs beyond the conventional methods of dimensionality reduction and excessive chloride incorporation.

Automated summary

Efficient blue perovskite light-emitting diodes (PeLEDs) have been a challenge, with only promising results in the sky-blue region. This study demonstrates deep-blue PeLEDs with guanidine (GA+)-induced perovskite emitters, achieving spectrally stable PeLEDs with a record external quantum efficiency (EQE) over 3.41%. The presence of GA+ stabilizes low-dimensional species, retarding energy transfer and facilitating deep-blue electroluminescence. This finding offers a new approach to achieve deep-blue PeLEDs.