CsPbCl3 perovskite is an attractive semiconductor material with characteristics such as a wide bandgap, high chemical stability, and excellent optoelectronic properties, which broaden its application prospects for ultraviolet (UV) and violet photodetectors (PDs). However, large-area CsPbCl3 films with high coverage, large grains, and controllable thickness are still difficult to prepare by using the solution method due to the extremely low solubility of their precursors in conventional solvents. Herein, a water-assisted confined re-growth method is developed, and a CsPbCl3 microcrystalline film with an area of 3 cm × 3 cm is grown, the thickness of which is controllable within a range of several microns. The as-prepared thin film exhibits a flat and smooth surface, large grains, and enhanced photoluminescence. Furthermore, the fabricated violet PDs based on the prepared CsPbCl3 film show a high responsivity of 2.17 A W-1, external quantum efficiency of 664%, on/off ratio of 2.58 × 103, and good stability. This study provides a prospective solution for the growth of large-area, large-grain, and surface-smooth CsPbCl3 films for high-performance UV and violet PDs.
Two-dimensional
(2D) Ruddlesden–Popper (RP) perovskites
are excellent optoelectronic materials due to their natural quantum
well structure and enhanced environmental stability. However, the
growth of their large-area high-quality thin films is still fundamentally
challenging. Herein, a novel gravity-guided growth method is proposed
to grow a wafer-scale (∼8 cm2) (PEA)2PbBr4 thin films (∼μm) with a centimeter-scale
crystal domain on an inclined substrate. A model is established to
elucidate the role of gravity in the growth process. It can be concluded
that the tip of the precursor solution on an inclined substrate should
be preferentially induced to nucleate and crystallize. In addition,
the crystallization growth is directionally guided and its velocity
increases as the rear contact angle decreases. Experimentally, the
controllable inclination angles can optimize the quality and thickness
of the films. Moreover, the arrayed photodetectors based on the resulting
(PEA)2PbBr4 thin films have been demonstrated
to have an extremely dark current of 10–12 A and
good environmental stability. After 100 days of storage in the atmosphere
for the unencapsulated samples, there is only a small photocurrent
degradation of 18%. This work provides a promising solution for scalable
fabrication of the large-area high-quality 2D perovskite thin films
that can serve as a good candidate for stable photodetectors.
Quasi two-dimensional (2D) perovskites are a new class of laser gain medium; however, the thickness of the solution-processed perovskite layer is usually too thin to support an optical mode due to the low solubilities of precursors. Here, we report a flexible large-area film transfer method to lengthen the cavity according to the resonant condition. Then a single-mode vertical-cavity quasi 2D (PEA)2Csn-1PbnX3n+1 (X:Br, Cl) perovskite pure green laser is demonstrated, which has a low threshold of 39.3 μJ/cm−2, a high-quality factor of 1159, and a highly linear polarization degree of 92.5% under nanosecond pulsed optical pumping. This is a significant step toward low-cost practical perovskite lasers.
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