Suchergebnisse

1 Esquema.- 4 Figuras ; The performance of organic thin film optoelectronic devices strongly relies on the nanoscale aggregate structure of the employed conjugated polymer. Their impact on electronic interface interactions with adjacent layers of graphene, widely reported to improve the device characteristics, yet remains an open issue, which needs to be addressed by an appropriate benchmark system. Here, we prepared discrete ensembles of poly(3-hexylthiophene) nanoparticles and graphene oxide sheets (P3HTNPs–GO) with well defined aggregate structures of either J- or H- type and imaged their photogenerated charge transfer dynamics across their interface by Kelvin probe force microscopy (KPFM). A distinctive inversion of the sign of the surface potential and surface photovoltage (SPV) demonstrates that J-aggregates are decisive for establishing charge transfer interactions with GO. These enable efficient injection of photogenerated holes from P3HTNPs into GO sheets over a range of tens of nanometers, causing a slow SPV relaxation dynamics, and define their operation as efficient hole-transport layer (HTL). Conversely, H-type aggregates do not facilitate specific interactions and entrust GO sheets the role of charge-blocking layers (CBL). The direct effect of P3HT's aggregate structure on GO's functional operation as HTL or CBL thus establishes clear criteria towards the rational design of improved organic optoelectronic devices. ; This work has received funding from the Spanish MINEICO (project grants ENE 2016-79282-C5-1-R and ENE 2016-79282-C5-4-R) and associated EU Regional Development Funds. A.M.B., E.I., and W.K.M. acknowledge funding from European Union's Horizon 2020 research and innovation programme under the Marie Skłodowksa-Curie grant agreement no. 642742. They also acknowledge the Gobierno de Aragón (Grupo Reconocido DGA T03_17R) and associated EU Regional Development Funds. We also acknowledge institutional support from the Unit of Information Resources for Research at the "Consejo Superior de Investigaciones Científicas" (CSIC) for the article-processing charges contribution. ; Peer reviewed

4 figures.-- Supplementary information available. ; Graphene oxide (GO) is widely used as a component in thin film optoelectronic device structures for practical reasons because its electronic and optical properties can be controlled. Progress critically depends on elucidating the nanoscale electronic structure of GO. However, direct experimental access is challenging because of its disordered and nonconductive character. Here, we quantitatively mapped the nanoscopic charge distribution and charge dynamics of an individual GO sheet by using Kelvin probe force microscopy (KPFM). Charge domains are identified, presenting important charge interactions below distances of 20 nm. Charge dynamics with very long relaxation times of at least several hours and a logarithmic decay of the time correlation function are in excellent agreement with Monte Carlo simulations, revealing an universal hopping transport mechanism best described by Efros–Shklovskii's law. ; This research was financed by the Ministerio de Ciencia e Innovación and the Agencia Estatal de Investigación (MICINN/AEI, Spain) and associated Funds of the European Union through the projects "Nano and Meso Scales: Modelling, Structure and Characterization" (PID2019-104272RB-C52/AEI/10.13039/501100011033 and "Photoelectrochemical hydrogen production by optimized graphene-based interfaces" (PID2019-104272RB-C51/AEI/10.13039/501100011033) and the Fundación Séneca through the projects 19907/GERM/15 and 20860/PI/18, as well as the Gobierno de Aragón (Grupo Reconocido DGA-T03_20R). ; E.C. acknowledges funding of his predoctoral contract by Spanish MINEICO and associated European Social Funds (BES2017-080020). ; Peer reviewed