Picosun, a provider of advanced atomic layer deposition (ALD) solutions, has announced the successful final outcomes of ROD-SOL, a three-year, inter-European project funded by the European Union 7th Framework Programme. The project has used silicon nanorod based concept in order to meet its objective of increasing solar cell efficiency at reduced cost of production.
The growth of the light-capturing nanorod forests over low-cost substrates such as flexible foils or glass will drastically decrease the required quantity of active photovoltaic materials such as silicon and also increase the cell’s durability and energy conversion efficiency to more than 9%.
Active surface area of the nanorod forest is very high thanks to its effective three-dimensional geometry, which allows it to absorb more light when compared to user-friendly two-dimensional thin film solar cells. Moreover, the p-n junction is located very near to the surface when compared to standard solar cells, thus significantly enhancing the transfer of the minority carrier charge, which in turn increases the amount of electricity generated by the cell.
Since the nanorod forests have dimensions in the micrometer or sub-micrometer range, the ALD method is suitable for producing certain key components of the solar cells. An ultrathin Al2O3 film has been used as a passivation layer, which is coated over the surface of the nanorods using the ALD method in order to eliminate recombination losses and thus prevent reduction in cell efficiency.
With its self-restricting, surface-controlled and gas-phase nature, the ALD method covers even the narrowest and deepest crannies and nooks between the rods with the homogenous passivation film devoid of defects and pin holes. In addition, the method proved its indispensability by producing high-quality transparent conductive oxide layer, a key cell component that serves as the current collector atop of the cell. Picosun developed a user-friendly and efficient high volume manufacturing batch ALD equipment for this purpose during the course of the project.