Creating Extrinsic Self-Trapped Excitons by Isoelectronic Doping for Lead-Free High-Efficiency Light Emission and...

Area of Science:

• Materials Science
• Solid-State Physics
• Photochemistry

Background:

• Metal-ion doping is crucial for enhancing light emission in metal halide perovskites via self-trapped excitons (STEs).
• Distinguishing between intrinsic and extrinsic STEs remains a challenge in the literature.
• Understanding extrinsic STEs is key to optimizing perovskite optoelectronic properties.

Purpose of the Study:

• To experimentally demonstrate and characterize an extrinsic STE in a metal halide perovskite.
• To investigate the mechanism behind extrinsic STE formation and its impact on luminescence.
• To explore the potential of extrinsic STEs for advanced material design and device applications.

Main Methods:

• Substitution of isoelectronic Cu+ for Ag+ in one-dimensional CsAg2I3 perovskite.
• Experimental characterization of photoluminescence and quantum efficiency.
• First-principles density functional theory (DFT) calculations.

Main Results:

• Copper doping transformed the nonemissive CsAg2I3 into an efficient extrinsic STE emitter with near-unity quantum efficiency at room temperature.
• DFT calculations revealed that Cu+ induces local lattice distortion, creating localized valence band states.
• These localized states effectively trap photoexcited holes, forming bound excitons and STEs.

Conclusions:

• Extrinsic STEs can be controllably engineered in metal halide perovskites.
• The Cu+-induced [CuI4]3- complex serves as an efficient extrinsic STE center.
• Extrinsic STEs hold significant promise for fundamental research and diverse device applications in perovskite optoelectronics.