Interface and Defect Engineering for Metal Halide Perovskite Optoelectronic Devices

Abstract

Metal halide perovskites have been in the limelight in recent years due to their enormous potential for use in optoelectronic devices, owing to their unique combination of properties, such as high absorption coefficient, long charge‐carrier diffusion lengths, and high defect tolerance. Perovskite‐based solar cells and light‐emitting diodes (LEDs) have achieved remarkable breakthroughs in a comparatively short amount of time. As of writing, a certified power conversion efficiency of 22.7% and an external quantum efficiency of over 10% have been achieved for perovskite solar cells and LEDs, respectively. Interfaces and defects have a critical influence on the properties and operational stability of metal halide perovskite optoelectronic devices. Therefore, interface and defect engineering are crucial to control the behavior of the charge carriers and to grow high quality, defect‐free perovskite crystals. Herein, a comprehensive review of various strategies that attempt to modify the interfacial characteristics, control the crystal growth, and understand the defect physics in metal halide perovskites, for both solar cell and LED applications, is presented. Lastly, based on the latest advances and breakthroughs, perspectives and possible directions forward in a bid to transcend what has already been achieved in this vast field of metal halide perovskite optoelectronic devices are discussed.

Steric Impediment of Ion Migration Contributes to Improved Operational Stability of Perovskite Solar Cells

“…Ag was used as the metal electrode, in which case the migration of I − toward the electrode to deplete the stoichiometry of the perovskite and the corrosion of the electrode by AgI formation is expected to be the major cause of device degradation, [37,54,55] while the more thermally stable poly[bis(4-phenyl)(2,4,6-trimethylphenyl) amine] (PTAA) was used as the hole transporting layer (HTL) to replace spiro-MeOTAD. [8,30,37,57,58] The AceMA device was seen to have significantly improved thermal stability, and retained almost 92% of its initial PCE after over 450 h of continuous heating. In contrast, the reference MA device degraded to just 1.6% of its initial PCE over the same time period.…”

Toward Efficient and Stable Perovskite Solar Cells: Choosing Appropriate Passivator to Specific Defects

“…The defects in perovskite films exert a dominating influence on the photovoltaic parameters of PSCs including the open‐circuit voltage ( V oc ), short‐circuit current density ( J sc ), and fill factor (FF). [ 29–31 ] When PSCs are under operation, the electrons are excited into the conduction band under light illumination, tearing the internal quasi‐Fermi levels in the perovskite layer, which is the origin of the V oc . [ 32 ] However, free carriers can be trapped by defects for nonradiative recombination, reducing the charge density and ultimately inducing a decrease in V oc .…”

Barrier Designs in Perovskite Solar Cells for Long‐Term Stability

“…[8] To further improve the efficiency and long-term stability of PSCs, researchers have explored various interlayers inserting into the basic "n-i-p" or "p-i-n" structure from the perspective of interface engineering. [9][10][11] Beyond the rapidly increased PCE, improving the device stability to meet the requirement of practical application remains as one of the major topics of PSCs development, since there is still a long distance from the required 20-25 years' operation lifetime for photovoltaic applications. [12] To date, many works have been dedicated to revealing failure mechanisms of PSCs.…”