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| Author(s): |
Andreia de Morais
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Química |
| Defense date: | 2015-11-12 |
| Examining board members: |
Ana Flávia Nogueira;
Edson Roberto Leite;
Roberto Mendonça Faria;
René Alfonso Nome Silva;
Italo Odone Mazali
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| Advisor: | Ana Flávia Nogueira |
| Abstract | |
The Doctoral Thesis aims to develop composite films based on titanium dioxide nanoparticles (TiO2) and reduced graphene oxide (RGO) for two applications: 1) as photoanodes for photoelectrochemical water splitting studies; 2) as electron transport layer (ETL) in organic solar cells with inverted configuration. In the first part of the work, the nc-TiO2/RGO films were prepared by sol-gel method with hydrothermal treatment and characterized by X ray diffraction, Raman spectroscopy, transient absorption spectroscopy (TAS), microscopy and electrochemical techniques. In general, the nc-TiO2 nanoparticles are predominantly in the anatase crystalline form and densely anchored on the RGO sheets. In the photoelectrochemical studies, the nc-TiO2/RGO (0.1 wt %) electrode had higher average photocurrent density value (0.20 mA cm-2 at 1.23 VRHE) in relation to other electrodes, with increased 78 % compared to standard film (0,11 mA cm-2 at 1.23 VRHE). No evidence for TiO2 sensibilization by the RGO sheets was observed. The TAS results showed an increase in the lifetime and yield of the photogenerated electrons and holes. Therefore, in films with lower concentration than 0.1 wt %, the RGO may act as an electron acceptor and transporter, decreasing the charge recombination processes and contributing to a significant improvement in photocurrent density value. In the second part of the work, thin and transparent TiO2/RGO films were prepared from the sol-gel method and the results indicated that the TiO2 nanoparticles are also predominantly the anatase crystalline form. The size and shape of RGO sheets vary greatly and these are distributed unevenly on the composite films. The best solar cells were obtained with TiO2/RGO (2.0 wt %) films and this behavior was independent of the use of V2O5 or PEDOT:PSS as hole transport layer (HTL). The KPFM images show that the presence of the RGO in the TiO2 film can promote a positive shift in the surface potential (SP) values. This suggests that the electrons are transported to the conductor substrate, while the holes remains on the surface of the composite films. The ability to collect electrons can be increased by incorporating RGO in the TiO2 matrix, resulting in an increase of the photocurrent density and power conversion efficiency of these solar cells (AU) | |
| FAPESP's process: | 10/18656-1 - Preparation and characterization of TiO2 and ZnO nanoparticles composites containing carbonaceous materials and their application in solar cells |
| Grantee: | Andreia de Morais |
| Support Opportunities: | Scholarships in Brazil - Doctorate |