Abstract
Considerable attention has been drawn to the lead halide perovskites (LHPs) because of their outstanding optoelectronic characteristics. LHP nanosheets (NSs) grown from single crystalline lead halide possess advantages in device applications as they provide the possibility for control over morphology, composition, and crystallinity. Here, free-standing lead bromide (PbBr2) single-crystalline NSs with sizes up to one centimeter are synthesized from solution. These NSs can be converted to LHP while maintaining the NS morphology. We demonstrate that these perovskite NSs can be processed directly for fabrication of photodetector and laser arrays on a large scale. This strategy will allow high-yield synthesis of large-size perovskite NSs for functional devices in an integrated photonics platform.
Highlights
Lead halide perovskites (LHPs) with the form APbX3 (A = inorganic or organic cation; X = halide anion) have attracted ever-increasing interest because of the high-efficiency solar cells which can be fabricated by solution methods
In spite of these efforts, there is still no report on centimeter-size nanosheets made of 2D perovskite till ; and the control over perovskite synthesis is still in its infancy compared with other semiconductor NSs22,23
Chen et al developed a space-limited inverse temperature crystallization (SLITC) technique to achieve the synthesis of submillimeter-size perovskite single crystal thin film, in which the key point is limiting the lateral growth of perovskite crystal in a confined space
Summary
The prepared PbBr2 NSs can be converted to methylammonium (MA) lead bromide perovskites by a vapor-solid reaction in MABr vapor. Comparing to the conversion in solution, the vapor-solid reaction can retain the morphology and crystallinity within the perovskite crystals while preventing the dissolution of PbBr2 and perovskite crystals in organic solvents[7,35,36]. The XRD pattern can be fully indexed to the orthorhombic phase of MAPbBr3, indicating the complete conversion from PbBr2 (Fig. 3e). By vapor-solid conversion from PbBr2, we obtain orthorhombic phase MAPbBr3 nanosheets rather than the cubic phase MAPbBr3 crystals which can be synthesized from solution[38]. The electron diffraction pattern shows that oriented highly crystalline domains are formed after conversion to LHP, these perovskite NS are very likely polycrystalline when we compare with vapor phase conversion of PbX217,24,37,39. The absorption spectrum indicates that the band edge is at 539 nm (2.3 eV, Fig. 3h). A low concentration of mid-gap defects is suggested by the steep rise in absorption at the band edge
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