Ultrabright Near-Infrared Lead-Free Perovskite Light-Emitting Diodes with Negligible Efficiency Roll-Off

Area of Science:

• Materials Science
• Solid-State Physics
• Optoelectronics

Background:

• Lead-free halide perovskites offer tunable optoelectronic properties for light-emitting diodes (LEDs).
• Efficiency roll-off in perovskite LEDs is a major limitation, caused by nonradiative recombination and structural instabilities.
• Tin-based perovskites (e.g., CsSnI3) are promising lead-free alternatives but face challenges.

Purpose of the Study:

• To engineer a lead-free tin perovskite semiconductor to enhance photoluminescence quantum efficiency (PLQE) and reduce efficiency roll-off in LEDs.
• To investigate the effect of molecular doping on charge-carrier concentration and lattice stability.
• To demonstrate the potential of the engineered perovskite for high-power optoelectronic applications.

Main Methods:

• Molecular engineering of CsSnI3 perovskite using N,N -diphenylthiourea (DPTA).
• Control of charge-carrier concentration and lattice growth.
• High-resolution transmission electron microscopy (HRTEM) to analyze film structure and strain distribution.
• Fabrication and characterization of near-infrared LEDs.

Main Results:

• Achieved a PLQE of 36% at a carrier concentration of 10^18 cm^-3 in DPTA-engineered CsSnI3.
• Uniform local strain distribution in doped films enhanced carrier wave-function overlap, boosting PLQE.
• Fabricated near-infrared LEDs with an external quantum efficiency (EQE) of 13.4% and peak radiance of 1248 W sr^-1 m^-2.
• Demonstrated minimal efficiency roll-off at current densities exceeding 3500 mA cm^-2.

Conclusions:

• DPTA doping is an effective strategy for enhancing the optoelectronic properties of lead-free tin perovskites.
• The engineered CsSnI3 shows significant potential for high-power optoelectronic devices, including LEDs.
• This work advances the development of lead-free perovskites for applications like electrically pumped laser diodes.