Optical and Electrical Investigations to Unveil Charge Storage and Transport Mechanisms in ITO Nanocrystals .

Transparent conducting oxide (TCO) zero-dimensional (0D) nanocrystals (NCs) such as Indium-Tin-Oxide (ITO) are of special importance for opto- electrical devices because of their unique features of optical transparency in the visible region and controllable electrical conductivity. In order to fully realize the potential of these materials to integrate them into useful devices, greater understanding of the charge transport in nanocrystal thin films along with a deep insight into the charge storage mechanism in solution is necessary¹. Doped metal oxide nanocrystals (MO NCs) are potential candidates for accumulating multiple electrons through the light induced doping process termed ‘Photodoping’. It has been demonstrated recently that metal oxide (MO) nanocrystals can act as nanocapacitors when coupled with a suitable system acting as hole or electron acceptor, storing the charges that are generated upon illumination with photon energy above the MO bandgap².ITO NCs with different In₂O₃ (IO) shell thicknesses are charged using a UV LED in a controlled and inert atmosphere, simultaneously monitoring the changes in the absorption spectra over time with time resolution of few seconds. In this way we extract information on the dynamics of the light-driven charging process of a set of ITO/In₂O₃ core/shell (ITO/IO) NCs with “artificial” depletion regions.³<br/>In addition, we leverage a metal-insulator-metal device configuration to probe the electronic transport in Tin doped Indium Oxide nanocrystals (ITO nanocrystals) to understand the electrical effects of photodoping.⁴ The electronic conduction in ITO NC thin film is studied in dark and light (UV) conditions in order to understand light- induced charge generation. ITO, being a wide bandgap material with high native doping levels, manifest electronic conduction that resembles semiconductor behaviour.<br/><br/>References:<br/><br/>(1) Ghini, M.; Curreli, N.; Camellini, A.; Wang, M.; Asaithambi, A.; Kriegel, I. Photodoping of Metal Oxide Nanocrystals for Multi-Charge Accumulation and Light-Driven Energy Storage. Nanoscale <b>2021</b>, <i>13</i> (19), 8773–8783. https://doi.org/10.1039/D0NR09163D.<br/><br/>(2) Kriegel, I.; Ghini, M.; Bellani, S.; Zhang, K.; Jansons, A. W.; Crockett, B. M.; Koskela, K. M.; Barnard, E. S.; Penzo, E.; Hutchison, J. E.; Robinson, J. A.; Manna, L.; Borys, N. J.; Schuck, P. J. Light-Driven Permanent Charge Separation across a Hybrid Zero-Dimensional/Two-Dimensional Interface. <i>J. Phys. Chem. C</i> <b>2020</b>, <i>124</i> (14), 8000–8007. https://doi.org/10.1021/acs.jpcc.0c01147.<br/><br/>(3) Ghini, M.; Curreli, N.; Lodi, M. B.; Petrini, N.; Wang, M.; Prato, M.; Fanti, A.; Manna, L.; Kriegel, I. Control of Electronic Band Profiles through Depletion Layer Engineering in Core–Shell Nanocrystals. <i>Nat. Commun.</i> <b>2022</b>, <i>13</i> (1), 537. https://doi.org/10.1038/s41467-022-28140-y.<br/><br/>(4) Müller, K.-H.; Wei, G.; Raguse, B.; Myers, J. Three-Dimensional Percolation Effect on Electrical Conductivity in Films of Metal Nanoparticles Linked by Organic Molecules. <i>Phys. Rev. B</i> <b>2003</b>, <i>68</i> (15), 155407. https://doi.org/10.1103/PhysRevB.68.155407.