Abstract
Serious performance decline arose for perovskite light-emitting diodes (PeLEDs) once the active area was enlarged. Here we investigate the failure mechanism of the widespread active film fabrication method; and ascribe severe phase-segregation to be the reason. We thereby introduce L-Norvaline to construct a COO−-coordinated intermediate phase with low formation enthalpy. The new intermediate phase changes the crystallization pathway, thereby suppressing the phase-segregation. Accordingly, high-quality large-area quasi-2D films with desirable properties are obtained. Based on this, we further rationally adjusted films’ recombination kinetics. We reported a series of highly-efficient green quasi-2D PeLEDs with active areas of 9.0 cm2. The peak EQE of 16.4% is achieved in <n > = 3, represent the most efficient large-area PeLEDs yet. Meanwhile, high brightness device with luminance up to 9.1 × 104 cd m−2 has achieved in <n> = 10 film.
Highlights
Serious performance decline arose for perovskite light-emitting diodes (PeLEDs) once the active area was enlarged
Transient absorption (TA) measurement was conducted to analyze this optical discrepancy between different regions (Supplementary Fig. 2)
The decay rates for the centerregion are much faster than those for the edge-region, illustrating better energy transfer efficiency, which can be the reason for photoluminescence quantum yield (PLQY) enhancement
Summary
Serious performance decline arose for perovskite light-emitting diodes (PeLEDs) once the active area was enlarged. High-quality large-area quasi-2D films with desirable properties are obtained. Fast and homogeneous crystallization is the prerequisite to guarantee high-quality quasi-2D film formation, which is the most important step in the whole PeLEDs fabrication[20,21]. Verifying the validity of the “antisolvent-assisted” approach, exploring the failure mechanism, and seeking new solutions are essential steps for developing high-performance, large-area quasi2D PeLEDs. Here, quasi-2D perovskite systems with a composition of PEA2(FA0.7Cs0.3)n−1PbnBr3n+1 (n = 2, 3, ..., ∞) are firstly employed to fabricate large-area PeLEDs. we find out that the traditional “antisolvent-assisted” approach does not work well for large-area PeLEDs manufacture. We conclude that the key to generate efficient large-area quasi-2D PeLEDs is to suppress the severe phase-segregation, in the edgeregion of the device. The new intermediate phase does change the crystallization pathway and facilitate the formation of large-area, high-quality quasi-2D films with desirable optical and electrical properties. The work paves the way for the future large-area PeLED manufacture
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