| AVS 60th International Symposium and Exhibition | |
| Energy Frontiers Focus Topic | Wednesday Sessions |
| Session EN+SE+SS+TF-WeM |
| Session: | Thin Films for Energy |
| Presenter: | J. Dorman, Universität Konstanz, Germany |
| Authors: | J. Dorman, Universität Konstanz, Germany J. Weickert, Universität Konstanz, Germany M. Putnik, Universität Konstanz, Germany L. Schmidt-Mende, Universität Konstanz, Germany |
| Correspondent: | Click to Email |
It has been shown over the last two decades that conversion efficiencies up to 12% can be achieved using TiO2 based solar cells, such as in the dye sensitized solar cell. Recently, there has been a push to replace these hazardous electrolytes with organic materials to create environmentally friendly devices with extended lifetimes. However, one of the limitation of these hybrid solar cells is electron-hole interaction across the metal-oxide and organic hole transporter interface.
In this work, we introduce core-shell nanostructured hybrid solar cells with a single crystal core in order to increase electron mobility and light scattering without additional recombination effects. Atomic layer deposition (ALD) was used to fabricate TiO2 nanowires (NWs) in order to take advantage of the directed electric field within the structures. The TiO2 NWs were grown in a template structure using titanium iso-propoxide and water as precursors, forming high aspect ratio arrays. During the growth process a Sn4+ dopant is introduced to create a doped Sn:TiO2 nanostructured array with increased electron mobility. After the NW growth, an additional ALD step is used to deposit a TiO2 layer, creating the core-shell structure. The dopant gradient within the core-shell structure causes the electrons to migrate toward the core of the nanowire due to the lower energy conduction band, potentially reducing electron-hole recombination at the TiO2:P3HT interface. The conduction band engineering has a similar effect as that seen with dipole modification of the interface. Additionally, the surface can be further modified with dye molecules. This doped core-shell structure has resulted in a conversion efficiency of 2 % with a surface treatment of the squaraine dye SQ2. This increase in efficiency is due to the contribution of the P3HT in the photon conversion, which is limited in various dyes due injection of electrons caused by the conduction band offset. Furthermore, the engineered energy levels and interfacial modifiers have a significant effect on the external quantum efficiency and internal resistances, as determined using various characterization methods.