Photo-induced charge transfer in composition-tuned halide perovskite nanocrystals with quinone and its impact on conduction current

Abstract

A facile interfacial charge transfer (CT) with a reduced inter-layer energy band regulates the charge transport mechanism in any optoelectronic device. The enhancement in semiconductor-based device performance often demands improved CT dynamics and collection of free carriers with reduced charge recombination. In this work, we present a detailed inspection of the photo-induced CT between inorganic lead halide perovskite nanocrystals (PNCs) with varied compositions and their consequence on the charge transport process. The superior CT rate in mixed halide CsPbBr2Cl PNCs with naphthoquinone (NPQ) is revealed when compared with the parent CsPbBr3 PNCs and its anion-exchanged counterpart CsPbCl3. The glimpses of hole transfer contribution along with electron transfer are detected for CsPbBr2Cl with superior CT efficiency. The enhanced conduction current after the insertion of NPQ into the PNCs with a reduced hysteresis suggests an improved charge transport in the fabricated device compared to the pristine PNCs. These findings can contribute to a better understanding of multiple ways of engineering optoelectronic devices to boost performance and efficiencies and the concurrent role of the CT process in the conduction mechanism.

Deciphering the Relevance of Quantum Confinement in the Optoelectronics of CsPbBr3 Perovskite Nanostructures

“…The K bind values follow a trend similar to that of k q and are higher for the PNPL (19.5 × 10 4 M –1 ) than for the PQD (3.6 × 10 4 M –1 ) and PNR (1 × 10 4 M –1 ). These K bind values are comparable to those of the system of PNCs with NPQ . For a suitable presentation, the k q and K bind values are plotted with their respective dimensionality in Figure c.…”

“…The k q is higher for the PNPL (14.3 × 10 11 M –1 s –1 ), followed by the PQD (1.4 × 10 11 M –1 s –1 ) and PNR (0.1 × 10 11 M –1 s –1 ). The order of magnitude of k q is found to be 2 times higher than that of the PVK PNC, indicating the role of quantum confined dimension on photoinduced CT. However, the nonlinearity of the plot of I 0 / I versus [NPQ] for the PNPL suggests the contribution of dynamic and static quenching in the PNPL, while the linearity in the PQD and PNR directs only one mode of quenching.…”

“…This is in good agreement with previous literature reports on the PNPL. − Gaussian fitting to the size distribution histograms yields an average edge length of 165 nm with a thickness of 2.1 nm, suggesting the formation of the three-monolayer PNPL. PNPL structures with two and three monolayers with 1.2 and 2 nm thicknesses have been synthesized with a similar protocol by Bohn et al The TEM micrographs of the as-synthesized PQD reflect a cubic structure (Figure b). , The highly crystalline PQD possesses a crystal lattice spacing of 4.3 Å (Figure e), while the size distribution gives an edge length of around (9.18 ± 0.22) nm (Figure h). Again, the PNR shows an elongated structure like typical nanorods (Figure c) with a lattice spacing of 4.2 Å (Figure f).…”

“…Such an alteration in the CT rate can also be explained by considering the energy level diagram, as shown in panels a and b of Scheme . The valence band maxima (VBM) and conduction band minima (CBM) of the PVK nanostructures are taken from the literature, ,, while the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of NPQ are calculated in our previous report Scheme b deciphers the possibility of electron transfer (ET) from the CBM of the nanostructures to the LUMO of NPQ.…”

“… a The VBM and CBM of the nanostructures were taken from refs , , and , and the HOMO and LUMO of NPQ were taken from ref . …”