Temperature-Dependent Electric Field Poling Effects in CH₃NH₃PbI₃ Optoelectronic Devices

Area of Science:

• Materials Science
• Solid-State Physics
• Photovoltaics

Background:

• Organo-lead halide perovskites exhibit promising optoelectronic properties for solar cells.
• Inconsistent forward-backward current-voltage (I-V) characteristics, known as hysteresis, hinder device performance and commercialization.

Purpose of the Study:

• To elucidate the underlying mechanisms responsible for hysteresis in organo-lead halide perovskite devices.
• To investigate the temperature-dependent behavior of hysteresis and its relation to ionic and dipole contributions.

Main Methods:

• Fabrication of transverse methylammonium lead iodide (CH3NH3PbI3) based devices.
• Measurement of photocurrent and photoluminescence under electric field poling across a temperature range (300 K to 10 K).
• Application of a magnetic field to probe the ionic diffusion contribution.

Main Results:

• Hysteresis diminishes at cryogenic temperatures (10 K), indicating the freezing of ionic diffusion.
• Continuous poling at low temperatures induces a built-in electric field and photovoltaic effect due to ion accumulation.
• Photoluminescence changes reveal a secondary dipole-related mechanism linked to organic cation alignment, enhancing radiative recombination.

Conclusions:

• Hysteresis in hybrid perovskites arises from a combination of mobile ion diffusion and a dipole-related mechanism.
• Understanding these dual mechanisms is crucial for developing stable and efficient perovskite solar cells.