Interfacial Trap-Assisted Triplet Generation in Lead Halide Perovskite Sensitized Solid-State Upconversion

Area of Science:

• Materials Science
• Photophysics
• Renewable Energy

Background:

• Photon upconversion via triplet-triplet annihilation (TTA) is key to exceeding the Shockley-Queisser limit in solar cells.
• Bulk perovskites are emerging as efficient sensitizers in solid-state upconversion devices, overcoming limitations of earlier nanocrystal-based systems.
• Understanding perovskite-sensitized triplet generation is challenging due to difficulties in controlling interfacial properties.

Purpose of the Study:

• To investigate the impact of interfacial properties on perovskite-sensitized photon upconversion.
• To elucidate the photophysical mechanisms governing triplet generation at the perovskite interface.
• To provide guidance for optimizing upconversion devices through interfacial engineering.

Main Methods:

• Mild surface solvent treatment to tune perovskite surface properties without altering bulk characteristics.
• Thermal evaporation of the annihilator to prevent solvent contamination.
• Analysis of upconversion performance, transient photoluminescence dynamics, and magnetic field dependence.

Main Results:

• Interfacial trap density correlates counterintuitively with increased upconversion brightness.
• Upconversion efficiency varied by an order of magnitude with different solvent treatments.
• Evidence for sequential charge transfer and trap-assisted triplet sensitization was observed.
• Incomplete triplet conversion and triplet-charge annihilation (TCA) were identified.

Conclusions:

• Interfacial control is critical for optimizing perovskite-based upconversion devices.
• Surface solvent treatment offers a viable method for tuning device performance.
• The findings guide the design of next-generation solar cells utilizing photon upconversion.