Abstract
Titanium dioxide represents one of the most widely studied transition metal oxides due to its high chemical stability, non-toxicity, abundance, electron transport capability in many classes of optoelectronic devices and excellent photocatalytic properties. Nevertheless, the wide bang gap of pristine oxide reduces its electron transport ability and photocatalytic activity. Doping with halides and other elements has been proven an efficient defect engineering strategy in order to reduce the band gap and maximize the photocatalytic activity. In the present study, we apply Density Functional Theory to investigate the influence of fluorine and chlorine doping on the electronic properties of TiO2. Furthermore, we present a complete investigation of spin polarized density functional theory of the (001) surface doped with F and Cl in order to elaborate changes in the electronic structure and compare them with the bulk TiO2.
Highlights
Titanium dioxide represents one of the most widely studied transition metal oxides due to its high chemical stability, non-toxicity, abundance, electron transport capability in many classes of optoelectronic devices and excellent photocatalytic properties
When titanium dioxide is doped with Ni the band gap decreases to 2.57 eV,[33] whereas when it is doped with Cl mid gap states are formed and the band gap decreases to 3 eV31
A profound band gap reduction can be beneficial to the material’s photocatalytic activity as it results in higher absorption of visible light, it might create mid gap states that usually act as charge traps having a negative impact on the performance of organic and perovskite solar cells utilizing TiO2 exclusively as electron transport/extraction material[39]
Summary
Titanium dioxide represents one of the most widely studied transition metal oxides due to its high chemical stability, non-toxicity, abundance, electron transport capability in many classes of optoelectronic devices and excellent photocatalytic properties. A profound band gap reduction can be beneficial to the material’s photocatalytic activity as it results in higher absorption of visible light, it might create mid gap states that usually act as charge traps having a negative impact on the performance of organic and perovskite solar cells utilizing TiO2 exclusively as electron transport/extraction material[39]. In those cases the photocatalytic ability of TiO2 should be suppressed as it degrades its interface with organic/perovskite semiconductor. Such states are highly beneficial for the photocatalytic applications of TiO2 though they can be detrimental for OSCs and PSCs performance as they constitute trap sites for the photogenerated charge carriers significantly reducing the device photocurrent
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