Tuning Charge Carrier Dynamics and Surface Passivation in Organolead Halide Perovskites with Capping Ligands and Metal Oxide Interfaces

Abstract

Electro-Optical Materialshalide perovskite materials now exceed 20% power conversion efficiency, [1] and much progress has been made using these materials in other applications such as light-emitting diodes (LEDs) [2] and photodetectors. [3] The combination of advantageous optoelectronic properties (high absorption coefficient and long charge carrier diffusion lengths under operating conditions) and solution-based syntheses has spurred the investigation of morphological control of such materials. Time-resolved optical spectroscopies provide established methodologies to probe excited state dynamics, and have been key tools in developing our understanding of excited state dynamics of organolead halide perovskite materials. [4] Recent advances in synthetic procedures have led to the controlled formation of low dimensionality perovskite structures in order to tune their physical properties. [5] Solar cells made from layered 2D perovskites show greater moisture stability compared to devices prepared from 3D perovskites, [6] and 2D/3D mixtures have been shown to be promising for stable solar cells that retain high efficiency. [7] 0D perovskite nanoparticles (NPs) have attracted much attention to modify the optoelectronic properties of perovskite materials through quantum confinement. [8] Photophysical studies have shown that the size and morphology of perovskite crystallites influence their excited state dynamics. Key properties such as the recombination rate constants and charge carrier mobility can vary with changes

Interfacial Engineering of Metal Oxides for Highly Stable Halide Perovskite Solar Cells

“…In any case, different studies have demonstrated the possibility of attaching organic modifiers on insulating oxides and the effect on charge carrier dynamics. Durrant and co‐workers recently reported on the growth of halide perovskite material within mesoporous Al 2 O 3 oxide and the passivation effect on trap sites . They suggested that the passivation of traps originates via the reduction in the amount of exposed Pb ions (similar to a ligand‐capped surface), as shown in Figure .…”

“…The latter influences the growth of the halide perovskite crystallites, and is probably affected by the type of oxide and its acidity (higher acidity is found in silica than in Al 2 O 3 ). Improved trap passivation is also observed at the perovskite/Al 2 O 3 interface in comparison with the perovskite/TiO 2 interface . ZrO 2 is another scaffold oxide applied in screen printing and highly stable C‐based PSCs.…”

Grain Boundary Enhanced Photoluminescence Anisotropy in Two‐Dimensional Hybrid Perovskite Films

“…Recently, the efficiency of hybrid perovskite optoelectronic devices has been greatly improved and is comparable to those based on single‐crystalline semiconductors, although their polycrystalline active layers contain numerous grain boundaries . Previous studies reveal that the in‐gap states created by the boundaries are mainly shallow traps at only a few millielectron volts below the band gap, which can contribute to both the exciton dissociation for carrier generation and the charge recombination for light emission . The in‐gap state is therefore essential for optimizing the optical and optoelectronic performance of perovskite materials.…”

Functional Metal Oxides in Perovskite Solar Cells

“…However, the problem of stability still limits the commercialization of PSCs. [57,58,59] Al 2 O 3 is usually employed as a growth framework for perovskite materials. Two main reasons affect device stability: On the one hand, it may relate to the stability of the perovskite material itself, including thermal stability and humidity stability; on the other hand, it is the stability of the structure, mainly involving the ETL and the HTL of the device structure.…”

“…[56] Insulated oxides, such as Al 2 O 3 , ZrO 2 , and SiO 2 , have also been widely used in PSCs to increase the stability of the perovskite material. [57,58,59] Al 2 O 3 is usually employed as a growth framework for perovskite materials. Because alumina has no oxygen vacancy defects, which is common in porous TiO 2 , the devices containing the Al 2 O 3 framework also show improved stability.…”