Novel Rapid Reprecipitation with Passivation Engineering for Fast Responsive and Durable Perovskite Photodetectors

To develop the perovskite formation process, it becomes necessary to explore the fabricating principles underlying the photosensitive layers. To this end, various aromatic solvents with different functional groups (such as methylbenzene and chlorobenzene (CB)) are selected and analyzed during perovskite crystallization [1]. This demonstrates the excellent detectivity and fast response speed of the perovskite photodetector treated with CB, owing to its enhanced interfacial affinity with ETL and improved charge dynamic behavior. Thus, this showcases the optimization of morphological affinity and the realization of a fast and highly sensitive photodetector via selective use of anti-solvents. Meanwhile, the strategy of a highly sensitive photodetector fabrication is introduced via the relaxation effect of perovskite intermolecular exchangers [2]. Chloronaphthalene (CN) is utilized to fabricate high-quality photosensitive layers in a perovskite nucleation environment due to the unique properties of CN, such as its high boiling point and bulky naphthalene ring. Steric hindrance is thereby induced in the perovskite adduct step, delaying intermolecular interactions and creating a stable perovskite nucleation environment which promotes grain growth. Accordingly, higher crystallinity and larger grains are found in CN treated thin films. Based on this, photodetector performance is greatly improved due to the development of long grain boundary lengths as grain size increases. This is because the increase in shunt resistance and ohmic shunt within the device are suppressed, leading to improved charge transfer and recombination properties. This demonstrates improved device stability, with photodetector parameters observed for approximately 1000 hours. An advanced method for controlling the adduct phase of perovskite via 1,8-octanedithiol additive (1,8-ODT) engineering is presented [3]. In this process, 1,8-ODT is utilized as an anti-solvent additive, forming a coordination bond with Pb²⁺ ions and facilitating rapid perovskite phase conversion. The optimized photodetector exhibits low dark current density, as well as high responsivity and detectivity at 680 nm. Based on this, stability test reveals that the performance remains at approximately 90% even after approximately 260 hours. The properties of stable and recoverable perovskite photodetectors are introduced via moisture trap engineering [4]. Perovskite decomposition mechanism by moisture and the effect of moisture trap introduction are specifically proposed. The degree of hydration and perovskite photodetector characteristics are compared via solubility changes based on each H₂O content. As a result, stable photodetector driving characteristics are reproducibly observed despite moisture content when moisture trap engineering is introduced. Finally, we propose a highly sensitive photodetection strategy via passivation engineering, specifically silica nanocrystal encapsulation [5]. We designed quantum dots (QD@APDEMS) based on silane barriers with hydrophobic ligands. These quantum dots exhibit excellent dispersibility and durability, facilitating an effective film formation. This approach is applicable to bulk perovskite photosensitive layers. As a result, the introduction of QD@APDEMS leads to an improvement in charge dynamics, attributed to perovskite grain expansion and the formation of films with fewer defects. This effect can be attributed to grain boundary passivation via QD@APDEMS. Furthermore, the deep HOMO level of QD@APDEMS effectively suppresses hole charge carrier injection and shunt leakage.<br/><br/>[1] Kim, B. G., et al. (2022). Int. J. Energy Res., 46(7), 9748-9760.<br/>[2] Chun, J. Y., Kim, B. G., et al. (2022). Appl. Surf. Sci, 591, 153207.<br/>[3] Kim, B. G., et al. (2023) J. Alloys Compd (Special Issue)., 172299.<br/>[4] Kim, B. G et al. (2022). J. Ind. Eng. Chem., 116, 331-338.<br/>[5] Chun, J. Y., Kim, B. G., et al. (2023). Carbon Energy, e350.