Enhanced Photoelectric Properties of CsPbBr 3 by SiO 2 and TiO 2 Bilayer Heterostructures.

CsPbBr 3 /SiO 2 heterostructures were synthesized by the hydrolysis reaction of a mixture of CsPbBr 3 nanocrystals (NCs) and (3-aminopropyl)triethoxysilane (APTS) in air. Compared with CsPbBr 3 NCs, the CsPbBr 3 /SiO 2 heterostructures exhibit stronger photoluminescence (PL) intensity, longer lifetime of PL (∼40.5 ns), and higher PL-quantum yield (PLQY, ∼86%). The carrier dynamics of CsPbBr 3 /SiO 2 was detected by the transient absorption (TA) spectrum. The experimental results show that SiO 2 passivates the surface traps of CsPbBr 3 NCs and enhances the PL intensity. However, photoelectrochemical impedance spectra (PEIS) demonstrate that the impedance of CsPbBr 3 /SiO 2 is higher than that of CsPbBr 3 NCs, which reduces carrier transport and extraction. Because the application of CsPbBr 3 /SiO 2 in optoelectronics is limited, CsPbBr 3 /SiO 2 /TiO 2 heterostructures were synthesized by the further reaction of tetrabutyl titanate (TBT). The TiO 2 coating can reduce the impedance of the CsPbBr 3 /SiO 2 . Importantly, ∼68% of the PL intensity of CsPbBr 3 /SiO 2 is retained. Compared with CsPbBr 3 /SiO 2 and CsPbBr 3 NCs, the CsPbBr 3 /SiO 2 /TiO 2 demonstrates faster carrier transport (κ ct = 2.4 × 10 9 s -1 ) and higher photocurrent density ( J = 76 nA cm -2 ). In addition, CsPbBr 3 /SiO 2 /TiO 2 shows good stability under (ultraviolet) UV irradiation, along with water stability and thermal stability. Therefore, the double protection approach can enhance the stability of CsPbBr 3 NCs and tune the optoelectronic properties of CsPbBr 3 NCs.