Abstract
In this work we demonstrate a novel approach to achieve efficient charge separation in dimensionally and dielectrically confined two-dimensional perovskite materials. Two-dimensional perovskites generally exhibit large exciton binding energies that limit their application in optoelectronic devices that require charge separation such as solar cells, photo-detectors and in photo-catalysis. Here, we show that by incorporating a strongly electron accepting moiety, perylene diimide organic chromophores, on the surface of the two-dimensional perovskite nanoplatelets it is possible to achieve efficient formation of mobile free charge carriers. These free charge carriers are generated with ten times higher yield and lifetimes of tens of microseconds, which is two orders of magnitude longer than without the peryline diimide acceptor. This opens a novel synergistic approach, where the inorganic perovskite layers are combined with functional organic chromophores in the same material to tune the properties for specific applications.
Highlights
Introduction of theperylene diimides (PDI) molecules in the ligand shell of the NPLs again leads to striking changes in the transient absorption (TA) spectrum (Fig. 3b)
The perovskite NPLs and PDI molecules were synthesized with the aim to selectively photoexcite both components at different wavelengths and study the possibility of electron transfer (ET) from the NPLs to the PDI molecules, as well as hole transfer (HT) from the PDI molecules to the NPLs (Fig. 1a, c). 2D colloidal CsPbBr3 NPLs (5 × 10 nm, thickness ~1.5 nm, 4 atomic monolayers (4ML)) were synthesized through a recrystallization method in which Cs-oleate and PbBr2 crystallize when acetone is added as antisolvent[26]
We have estimated from optical density measurements in hexane[39] that ~90 PDI molecules coordinate to the surface of the CsPbBr3 NPLs (Supplementary Note 2)
Summary
Introduction of thePDI molecules in the ligand shell of the NPLs again leads to striking changes in the TA spectrum (Fig. 3b). The XB feature at 453 nm has the same shape as observed for the CsPbBr3 NPLs (Fig. 3a), it decays much faster. This is shown, where the kinetics at the maximum of the exciton bleach of the NPLs with and without PDI are compared. The first is a reduced absorption (bleach) in the region from 470 to 540 nm, corresponding to the ground state absorption of the PDI molecule (Fig. 1d). That the photoinduced absorption of the PDI− in Fig. 3b inset is different from the induced absorption due to the excited state of free PDI
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