2022 Small Structures, Stability Improved! Exploring the Effect of Terminal Groups on Low-Dimensional Perovskites
SS-X solar simulator makes the breakthrough possible!
Small Structures (IF 11.459) published a study by Letian Dou of Purdue University and others in January 2022. Metal halide perovskites have excellent properties and can be used in solar cells, detectors, and other fields. The efficiency of perovskite solar cells (PSCs) has recently exceeded 25%. However, during the fabrication process, numerous crystal defects are formed on the surface and grain boundaries of the perovskite layer, which will affect the stability of PSCs. To address this problem, one approach is to develop low-dimensional perovskites (2D, 1D, and 0D), which exhibit enhanced stability and more structural and compositional versatility comparing with the 3D perovskites. The electronic and optical properties of 2D perovskites can be further tuned if organic molecules are incorporated into 2D layered hybrid perovskites. However, at present, the interactions between the conjugated organic building blocks and the metal halide inorganic building blocks have not been fully studied.
To investigate the effect of different anchoring groups on the crystal structure, phase formation, and device performances, in this study, the research team designed and synthesized a series of functionalized-bithiophene organic ligands with FA (formamidinium), Im (imidazolium) and BIm (benzimidazolium) terminal groups, which can greatly influence the crystal structure of low-dimensional perovskites. They then synthesized a series of Pb- and Sn-based OSiPs (organic semiconductor-incorporated perovskites), hybrid structures with functional organic cations intercalated between inorganic octahedral frameworks. Ligands with Imand BIm terminal groups are able to successfully form 1D or 2D perovskites, while the ligand with FA terminal group induce perovskite octahedra distortion and form ” Step-Like ” structures.
The synthetic routes of ligands 2TFAI, 2TImI, and 2TBImI.
Enlitech’s solar simulator and other instruments were used in this study to assist in the measurement. It was found that the terminal groups of the ligands have significant effect on the interactions between ligands and octahedrain perovskites, which in turn affect the formation of the crystal structures. Only the 3Dperovskite solar cells passivated by the ligands with Im and BIm terminal groups exhibit improved power conversion efficiencies and reduced hysteresis. This study shows that novel anchoring groups play a key role in determining the crystal structures and properties of OSiPs. The electronic and optical properties of these conjugated ligands with different end groups can be further studied to explore more potential applications.
A) Scheme of perovskite solar cell structure with ligand layer inserted between hole transporting layer and perovskite layer. B) J–V curves of devices with different passivation layers and in comparison with the control device without passivation layer. C) Champion J–V curves of control device and device passivated with 2TBImI, in both reverse scan and forward scan. D) EQE spectra of control device and device passivated with 2TBImI and the integrated photocurrent density, integrated over the AM1.5 solar spectrum.
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