Anisotropic Performance of High-Quality MAPbBr₃ Single-Crystal Wafers

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• Bulk single crystals of halide perovskites outperform polycrystalline forms in devices.
• High-quality, large single crystal growth is essential for optimal device performance.
• Understanding crystal anisotropy is key to harnessing halide perovskite potential.

Purpose of the Study:

• To develop an improved crystal growth system for halide perovskites.
• To investigate the anisotropy of optical, electronic, and radiation detection properties in methylammonium lead bromide (MAPbBr3) single crystals.
• To clarify the intrinsic dipole configuration within the pseudocubic crystal lattice.

Main Methods:

• Modified settled temperature and controlled antisolvent diffusion system for crystal growth.
• Fabrication of differently oriented crystalline wafers from bulk MAPbBr3 crystals.
• Characterization using X-ray rocking curves, optical spectroscopy, angle-resolved polarized Raman spectroscopy, and radiation detector fabrication.

Main Results:

• State-of-the-art MAPbBr3 crystals grown with exceptional crystalline quality (40-86 arcsec FWHM).
• Optical band gaps showed no anisotropy, while refractive index and extinction coefficient exhibited anisotropy.
• In-plane anisotropy observed in Raman spectra for (100) and (110) wafers, linked to MA+ orientations along <111>.
• Radiation detectors demonstrated photoresponse anisotropy, with performance order (100) > (110) > (111).

Conclusions:

• The study clarifies intrinsic dipole configurations in halide perovskite crystals.
• Quantitative data on physicochemical property anisotropy is provided, crucial for device optimization.
• Understanding and controlling crystal orientation is vital for maximizing halide perovskite device performance.