Overcoming the exciton binding energy in two-dimensional perovskite nanoplatelets by attachment of conjugated organic chromophores

Abstract

In this work we demonstrate a novel approach to achieve efficient charge separation in dimensionally and dielectrically confined two-dimensional perovskite materials. Twodimensional perovskites generally exhibit large exciton binding energies that limit their application in optoelectronic devices that require charge separation such as solar cells, photodetectors and in photo-catalysis. Here, we show that by incorporating a strongly electron accepting moiety, perylene diimide organic chromophores, on the surface of the twodimensional 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.

Conformational disorder of organic cations tunes the charge carrier mobility in two-dimensional organic-inorganic perovskites

“…It is worth mentioning that the difference in the φ value may affect the charge-carrier mobility deduced by OPTPS experiments. In principle, the value of φ is determined by the exciton binding energy (E b ) of the materials 39 . The value of E b of 2D OIHPs of [CH 3 (CH 2 ) n-1 NH 3 ] 2 PbI 4 ( n = 4, 6, 8, 9, 10, and 12) has been measured by Ishihara et al in terms of the difference between the bandgap and excitonic absorption peak in the low-temperature (5 K) absorption spectrum 40 .…”

Suppressing Strong Exciton–Phonon Coupling in Blue Perovskite Nanoplatelet Solids by Binary Systems

“…[19] Finally,t he femtosecond transient absorption (TA) spectra for agiven series of CsPbBr 3 NPL solids were taken to further explore the transfer and recombination dynamics of photogenerated carriers. [20] Forpure 2-ML CsPbBr 3 NPLs,itshows adominant photobleaching (PB, DA/A < 0) signature at 435 nm (Supporting Information, Figure S11). In turn to the pure 3-ML CsPbBr 3 NPLs,aweak shoulder PB band with ap eak at 445 nm matches with the steady state absorption onset representing state-filling of the conduction band.…”

Suppressing Strong Exciton–Phonon Coupling in Blue Perovskite Nanoplatelet Solids by Binary Systems

“…It would be worth identifying the fast energy transfer rates because as it is happening at the picosecond timescales, it can effectively compete with the phonon‐assisted processes, which are expected to take place in the ps‐level [19] . Finally, the femtosecond transient absorption (TA) spectra for a given series of CsPbBr 3 NPL solids were taken to further explore the transfer and recombination dynamics of photogenerated carriers [20] . For pure 2‐ML CsPbBr 3 NPLs, it shows a dominant photobleaching (PB, Δ A / A <0) signature at 435 nm (Supporting Information, Figure S11).…”