Ultralow Self-Doping in Two-dimensional Hybrid Perovskite Single Crystals

Area of Science:

• Materials Science
• Solid-State Physics
• Optoelectronics

Background:

• Unintentional self-doping in semiconductors, caused by defects, degrades optoelectronic device performance by affecting junction properties and increasing electronic noise.
• Solution-processed semiconductors, particularly hybrid perovskites, are prone to high defect concentrations due to rapid crystallization, exacerbating self-doping issues.

Purpose of the Study:

• To investigate and quantify self-doping levels in two-dimensional (2D) perovskites.
• To explore the impact of low self-doping concentrations on the performance of optoelectronic devices.
• To propose a mechanism for defect suppression in 2D perovskites with large organic cations.

Main Methods:

• Analysis of conductivity behavior in single crystals of 2D perovskites: (C6H5C2H4NH3)2PbI4·(CH3NH3PbI3)n-1 (n = 1, 2, and 3).
• Comparison of self-doping concentrations with typical three-dimensional (3D) hybrid perovskites.
• Fabrication and characterization of 2D perovskite photoconductors and investigation of their light-detectivity.

Main Results:

• Extremely low self-doping concentrations (over three orders of magnitude lower than 3D perovskites) were observed in the studied 2D perovskites.
• A correlation between large organic cations in hybrid perovskites and suppressed defect formation, leading to low self-doping, was proposed.
• Photoconductors based on these 2D perovskites exhibited extraordinarily high light-detectivity (10^13 Jones) due to reduced electronic noise.

Conclusions:

• The low self-doping in 2D perovskites significantly reduces electronic noise, making them ideal for sensitive light detection.
• Reduced equilibrium charge carrier concentration in these 2D perovskites benefits the design of p-i-n heterojunction solar cells by optimizing band alignment and enhancing charge extraction.