Highly efficient visible colloidal lead-halide perovskite nanocrystal light-emitting diodes (1801.10317v1)

Abstract: Lead-halide perovskites have been attracting attention for potential use in solid-state lighting. Following the footsteps of solar cells, the field of perovskite light-emitting diodes (PeLEDs) has been growing rapidly. Their application prospects in lighting, however, remain still uncertain due to a variety of shortcomings in device performance including their limited levels of luminous efficiency achievable thus far. Here we show high-efficiency PeLEDs based on colloidal perovskite nanocrystals (PeNCs) synthesized at room temperature possessing dominant first-order excitonic radiation (enabling a photoluminescence quantum yield of 71% in solid film), unlike in the case of bulk perovskites with slow electron-hole bimolecular radiative recombination (a second-order process). In these PeLEDs, by reaching charge balance in the recombination zone, we find that the Auger nonradiative recombination, with its significant role in emission quenching, is effectively suppressed in low driving current density range. In consequence, these devices reach a record high maximum external quantum efficiency of 12.9% reported to date and an unprecedentedly high power efficiency of 30.3 lm W-1 at luminance levels above 1000 cd m-2 as required for various applications. These findings suggest that, with feasible levels of device performance, the PeNCs hold great promise for their use in LED lighting and displays.

Colloidal Lead-Halide Perovskite Nanocrystal LEDs: A New Frontier in Solid-State Lighting

The paper offers a comprehensive paper on the development of highly efficient light-emitting diodes (LEDs) based on colloidal lead-halide perovskite nanocrystals (PeNCs). These materials have been gaining traction due to their favorable optical and electronic properties that make them suitable candidates for next-generation optoelectronic devices. The paper emphasizes improving the luminous efficiency of perovskite light-emitting diodes (PeLEDs), which has been a persistent challenge due to intrinsic material limits and device structural inefficiencies.

Photoluminescence and Efficiency Metrics

The authors achieve significant advancements by synthesizing colloidal MAPbBr$_3$ PeNCs under ambient conditions, reporting a photoluminescence quantum yield (PLQY) of 71% in solid film. Unlike bulk perovskites, which are hindered by slow bimolecular radiative recombination, these nanocrystals feature first-order excitonic radiation as the dominant emission mechanism. This paper meticulously analyzes the device dynamics to demonstrate how Auger non-radiative recombination is mitigated through achieving charge balance in the emission zone. This enhancement results in a record-breaking external quantum efficiency (EQE) of 12.9% and power efficiency of 30.3 lm/W at luminance levels above 1000 cd/m$^2$, setting a new benchmark for PeLEDs.

Implications and Comparisons

The work presents a comparative analysis of different electron transport layer (ETL) configurations to optimize charge injection and balance, thereby improving device performance substantially. Key observations indicate that controlled modifications in the ETL, such as blending components like B3PYMPM and TPBi, enable minimal leakage current and enhanced charge carrier balance, resulting in superior EQE and luminance. The paper posits that the structurally varied ETL blends not only fine-tune electron transport but also maintain lower driving voltages, which are crucial for securing high power efficiency, especially in practical applications where low power consumption is essential.

Theoretical and Practical Considerations

The theoretical framework developed in the paper corroborates experimental findings, emphasizing how charge density manipulation at the nanoscale can directly influence emission dynamics and efficiency rates in PeLEDs. The analysis captures the interplay between excitonic and Auger recombination processes and outlines the conditions under which PeNCs demonstrate their optimal luminescent properties, notably in the regime dominated by first-order excitonic radiation.

Practically, the implications of this paper are substantial; the promising luminance and efficiency metrics render PeNC-based PeLEDs a viable contender in the commercial LED market, specifically for applications demanding high brightness and low power consumption. The in-depth understanding of luminescence mechanisms in these materials also establishes a foundation for further exploration of halide perovskites in optoelectronics.

Future Developments in PeLEDs

Looking ahead, the progress achieved in this investigation serves as a catalyst for future research directed at enhancing the longevity and stability of PeLEDs, as current device half-lifetimes remain an obstacle. The exploration of diverse perovskite formulations and device architectures is suggested for future studies, with implications for expanding the practical utility of PeLEDs across broader spectral ranges and ambient conditions.

In conclusion, the research delineates significant strides in the field of lead-halide perovskite nanocrystal LEDs, offering a pathway towards efficient, highly luminous applications within solid-state lighting and displays. This work evidently stresses the critical role of surface passivation, charge carrier dynamics, and device engineering, advocating a systemic approach towards overcoming the existing limitations of perovskite-based optoelectronics.