The Trade-Off Between Efficiency and Electrical Stability in Green Mn²⁺ Doped Perovskite Light-Emitting Diodes

While light-emitting diodes (LEDs) made from lead halide perovskites have demonstrated external quantum efficiencies (EQEs) well over 20%, their electrical stability must be addressed before they are seriously considered for commercial applications. In an effort to improve the optoelectronic properties of lead halide perovskites for light emission, many researchers have investigated introducing both alkaline-earth metal ions (e.g., Ba²⁺ and Sr²⁺) and transition metal ions (e.g., Mn²⁺, Zn²⁺, Cd²⁺, and Ni²⁺) into the B-site of the perovskite’s ABX₃ structure. Additionally, the factors that limit the electrical stability of perovskite LEDs remain under investigation. In this work, 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 13.4% and a peak luminance of 95,400 cd/m². While the inclusion of TFPPO into the chloroform antisolvent dramatically increases the EQE of perovskite LEDs, the electrical stability is severely compromised. At an electrical bias of 5 mA/cm², our perovskite LED fabricated with a pure chloroform antisolvent (2.5% EQE) decays to half of its initial luminance in 90.68 minutes. Alternatively, our perovskite LED fabricated with TFPPO (13.4% EQE) decays to half of its initial luminance in 2.07 min. In order to investigate this trade-off in EQE and electrical stability, we study both photophysical and electronic characteristics before and after electrical degradation of the perovskite LEDs. We find that given identical electrical degradation conditions, the TFPPO-based device’s turn on voltage and overall electrical resistance increases in a much larger fashion as compared to the pure chloroform-based device. While the EQE characteristics of this Mn²⁺ doped perovskite LED show promise for B-site engineered perovskites, there is still large concern to simultaneously achieve both energy-efficient and electrically stable perovskite-enabled lighting. Uncovering the effects from the TFPPO additive on perovskite LEDs will reveal pathways on how to mitigate their negative consequences on electrical stability while retaining their energy-efficiency boosting properties.