Conductivity Tuning via Doping with Electron Donating and Withdrawing Molecules in Perovskite CsPbI₃ Nanocrystal Films

Abstract

Doping of semiconductors enables fine control over the excess charge carriers, and thus the overall electronic properties, crucial to many technologies. Controlled doping in lead-halide perovskite semiconductors has thus far proven to be difficult. However, lower dimensional perovskites such as nanocrystals, with their high surface-area-to-volume ratio, are particularly well-suited for doping via ground-state molecular charge transfer. Here, the tunability of the electronic properties of perovskite nanocrystal arrays is detailed using physically adsorbed molecular dopants. Incorporation of the dopant molecules into electronically coupled CsPbI 3 nanocrystal arrays is confirmed via infrared and photoelectron spectroscopies. Untreated CsPbI 3 nanocrystal films are found to be slightly p-type with increasing conductivity achieved by incorporating the electron-accepting dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4 TCNQ) and decreasing conductivity for the electron-donating dopant benzyl viologen. Time-resolved spectroscopic measurements reveal the time scales of Auger-mediated recombination in the presence of excess electrons or holes. Microwave conductance and field-effect transistor measurements demonstrate that both the local and long-range hole mobility are improved by F 4 TCNQ doping of the nanocrystal arrays. The improved hole mobility in photoexcited p-type arrays leads to a pronounced enhancement in phototransistors.

In Situ Ligand Bonding Management of CsPbI3 Perovskite Quantum Dots Enables High‐Performance Photovoltaics and Red Light‐Emitting Diodes

“…The longer lifetime is 5.8 ns, representing about 44 % of the total decay. In contrast, the faster lifetime of GSB decay for the L‐PHE passivated QDs is increased to 455 ps, with an amplitude representing ≈55 % of the total decay, confirming again the reduced surface states for QDs treated by L‐PHE [44] …”

In Situ Ligand Bonding Management of CsPbI3 Perovskite Quantum Dots Enables High‐Performance Photovoltaics and Red Light‐Emitting Diodes

“…Forthe pristine QD sample,t he faster decay lifetime of these two components is 317 ps,with an amplitude representing about 56 %ofthe total decay.T he longer lifetime is 5.8 ns,r epresenting about 44 % of the total decay.Incontrast, the faster lifetime of GSB decay for the L-PHE passivated QDs is increased to 455 ps,with an amplitude representing % 55 %ofthe total decay,confirming again the reduced surface states for QDs treated by L-PHE. [44] Meanwhile,t he temperature-dependent (300 Kt o8 0K) emission spectra (Supporting Information, Figure S6) were also measured for pristine and L-PHE treated CsPbI 3 QD films,asshown in Figure 4d-e.T he shift of emissions peak is mainly due to the different minima on the potential energy surface of relaxed excited state.W ec an also observe decreased emission intensity and increased full widths at half maximum (FWHM) of the emission peak with higher temperatures,w hich can be described by thermal quenching at configurational coordinate diagram. [46] Note that the shoulder emission peak around 710 nm at low temperature for the L-PHE passivated samples is originated from the coupling of L-PHE ligands with the host QD lattice.…”

Perovskite Nanocrystals: Synthesis, Stability, and Optoelectronic Applications

“…PNCs possess excellent optoelectronic properties, i.e., tunable bandgaps, narrow emission, strong light‐absorption coefficients, high PLQYs, and high defect tolerance, which pave the way for designing highly efficient PNC‐based optoelectronic devices, for example, laser [ 152,153 ] , field‐effect transistor (FET), [ 154–157 ] SCs, LEDs, and PDs. The promising progress and recently reported achievements in the application fields of SCs, LEDs, and PDs are briefly reviewed in the following sections.…”