Free-standing Single-walled Carbon Nanotube-CdSe Quantum Dots Hybrid Ultrathin Films For Flexible Optoelectronic Conversion Devices

Hybrid nanostructures from different nanomaterials are attracting increasing attention due to thepossibility of tuning their chemical, electronic, and optical properties over a wide range. So far, researchhas focused on the combination of one-dimensional (1D) systems such as nanotubes and nanowires withzero-dimensional (0D) objects such as semiconductor or metal nanoparticles. Carbon nanotubes andsemiconductor nanocrystals (quantum dots) because of their unique optical and electrical properties, basedon their composite has great application prospects and development potential in the fields of optoelectronicdevices. Especially, prepared two-dimensional hybrid films structure are of great significance in exploitinglarge-area, low-cost, and flexible electronic and optoelectronic devicesHere, we described a facile route for the fabrication of free standing single walled carbon nanotubes(SWNT)-CdSe quantumn dots (QDs) hybrid ultrathin films and investigated their optoelectronic conversionproperties. A free standing SWNT film with thickness of~36nm was firstly prepared via a wet process.The film was then immersed into the pre-synthesized oleic acid capped CdSe QDs (average diameter of3.5nm) solution, where CdSe QDs anchored spontaneously onto the surface of SWCNT film to produceSWNT-CdSe QDs hybrid film. To increase the interaction between SWNTs and CdSe QDs, the hybridfilms were annealed at300°C in Ar for30minutes. Transmission electron microscopy (TEM), confocallaser scanning microscopy, UV-visible absorption spectroscopy, fluorescence spectroscopy and FourierTransformed Infrared Spectroscopy (FT-IR) were used for the characterization before and after theannealing of the hybrid films, it was found efficient electron transfer from photoexcited CdSe QDs toSWNTs after annealing treatment. Based on the SWNT/CdSe QDs ultrathin composite films, by using pure SWCNT films in differentthicknesses as bottom and top electrodes, a flexible all carbon electrode optoelectronic conversion devicewith sandwich structure of SWCNT film (thickness of～200nm)/SWCNT/CdSe QDs hybrid film(thickness of~36nm)/SWCNT film (thickness of~36nm) was constructed to generate optoelectronicconversion under illumination of solar simulated light. Our results demonstrated that the all carbonelectrode structure was effective for charge separation and a sensitive and stable photocurrent signal couldbe produced in such a device. In addition, our SWCNT-CdSe QDs hybrid film exhibited high flexibility anddurability. No clear change in resistance of the film was detected under bending in various bending angles.