Inorganic nanostructures/organic polymer-based hybrid photovoltaic devices are an attractive future alternative to conventional solar cell technology due to the potential of low cost fabrication processes. However, optimising the efficiency of hybrid solar cells remains a key issue [1-4]. With exciton diffusion lengths in conducting organic materials, of approximately 10 nm, a device geometry whereby the hole and electrons can be separated and efficiently transported is required. Hence optimising the area of the active interface should optimise the device performance.
Here, ZnO NW hybrid cells have been fabricated using nanowires with a high level of control using low temperature solution based synthesis [2]. Arrays of nanoscale metal-oxide nanowires shown in figure 1 (a) are an example of highly ordered ZnO nanowires fabricated by hydrothermal growth methods at low temperature. Changes to the nanostructure morphology are achieved by maintaining the same growth solution and temperature, either by adding small volumes of ammonia, figure 1 (b) to produce randomly ordered NW structures or by extending the NW growth times to 2 days, figure 1 (c), to achieve perpendicular microtubular ZnO arrays.
The characteristics of nanostructured ZnO hybrid solar cells will be discussed with emphasis on the morphology and junction area dependence of the photovoltaic properties.
References:
1 J. B. Baxter et al. Appl. Phys. Lett. 86 053114 (2005).
2 M. Law et al, Nature Materials 4 455 (2005).
3 D. C. Olson et al, Thin Solid Films 496 26 (2006).
4 A. M. Peiró,et al. Chem. 16 2088 (2006).