Trade-off Between Efficiency and Stability in Mn²⁺-Doped Perovskite Light-Emitting Diodes

While light-emitting diodes (LEDs) made from metal halide perovskites have demonstrated external quantum efficiencies (EQEs) well over 20%, their device instability limits their commercial viability. In an effort to improve the optoelectronic properties of metal halide perovskites for light emission, many researchers have investigated introducing both alkaline-earth metal ions¹ (e.g., Ba and Sr) and transition metal ions² (e.g., Mn, Zn, Cd, and Ni) into the B-site of the perovskite’s ABX₃ structure. Additionally, the factors that limit the device stability of perovskite LEDs remain under investigation.<br/><br/>In this work,³ we dope Mn²⁺ ions into an organic-inorganic hybrid quasi-bulk 3D perovskite resulting into (PEABr)_0.2Cs_0.4MA_0.6Pb_0.7Mn_0.3Br₃ thin films with the addition of tris(4-fluorophenyl)phosphine oxide (TFPPO) dissolved in a chloroform antisolvent to achieve an EQE of 14.0% and a peak luminance of 128,000 cd/m². While the inclusion of TFPPO into the chloroform antisolvent dramatically increases the EQE of perovskite LEDs, the device stability is severely compromised. At an electrical current bias of 5 mA/cm², our perovskite LED fabricated with a pure chloroform antisolvent (2.97% EQE) decays to half of its maximum luminance in 37.0 minutes. Alternatively, our perovskite LED fabricated with TFPPO (14.0% EQE) decays to half of its maximum luminance in 2.54 min. In order to investigate this trade-off in EQE and stability, we study both photophysical and optoelectronic characteristics before and after PeLED electrical operation. By measuring repeated electrical scans and time-resolved photoluminescence spectra under identical degradation conditions for all Mn²⁺-doped perovskite LEDs, we find that with higher TFPPO-treated concentrations, there is decreased robustness in operational luminance, maximum luminance, turn-on voltage, and average decay lifetime. These results simultaneously illustrate the potential of efficient Mn²⁺-doped metal halide perovskites for light emission while also suggesting that further investigations are needed to mitigate stability degradation mechanisms induced by TFPPO treatment.<br/><br/><b>References</b><br/>1. M. Lu, X. Zhang, Y. Zhang, J. Guo, X. Shen, W. W. Yu, A. L. Rogach, “Simultaneous Strontium Doping and Chlorine Surface Passivation Improve Luminescence Intensity and Stability of CsPbI₃ Nanocrystals Enabling Efficient Light-Emitting Devices,” <i>Advanced Materials</i> 2018, 30, 1804691.<br/><br/>2. G. H. Ahmed, Y. Liu, I. Bravić, X. Ng, I. Heckelmann, P. Narayanan, M. S. Fernández, B. Monserrat, D. N. Congreve, S. Feldmann, “Luminescence Enhancement Due to Symmetry Breaking in Doped Halide Perovskite Nanocrystals,” <i>Journal of the American Chemical Society</i> 2022, 144, 34, 15862-15870.<br/><br/>3. S. Fernández, W. Michaels, M. Hu, P. Narayanan, N. Murrietta, A. O. Gallegos, G. H. Ahmed, J. Lyu, M. K. Gangishetty, D. N. Congreve, “Trade-off between efficiency and stability in Mn²⁺-doped perovskite light-emitting diodes,” <i>Device</i>, 1, 100017, 2023.