Improving polymer/ZnO hybrid solar cells through optimization of charge carrier transport and energy-band engineering (R-4649)

Organic/inorganic (hybrid) solar cells pose a very eligible alternative for classical silicon based photovoltaics, both with respect to ease of production (e.g. printing) and cost. Accordingly, there have been many reports lately on hybrid solar cells combining ZnO or TiO2 with poly(3-hexylthiophene) (P3HT). Their efficiencies, however, are still rather poor (< 2 %) as compared to those achieved for fully organic solar cells (+/-10 %), though the latter suffer from morphological instability. Even nanopatterned solar cells, offering a large active area for charge separation and a charge transport-friendly morphology, still perform below 1% for a ZnO/P3HT system, while these materials possess the physical properties to perform more than an order of magnitude better. Consequently, identifying the factors limiting the efficiencies of organic/inorganic solar cells still remains a challenging task. The main suspects as limiting factor are the electronic properties (energy level alignment) at the interface between the organic and the inorganic phase, and their individual bulk charge transport properties. Therefore, this project employs a two-fold strategy, starting from the P3HT/ZnO solar cell as model system. On the one hand it strives to carefully tune and balance the transport properties of both the organic and the inorganic phase by pursuing their optimal morphology. Secondly, the energetics at polymer/metal-oxide interfaces are modulated using molecular functionalization during the preparation of appropriate hybrid solar cells. The combination of these two pillars will allow to carry out an engineering approach to push the performance of organic/inorganic solar cells to significantly higher values.

Keywords:photovoltaic solar cells

Disciplines:Condensed matter physics and nanophysics