From Event: SPIE Organic Photonics + Electronics, 2017
The kinetics at contacts plays a crucial role in sandwich-type thin-film devices based on organic semiconductors. This is of particular importance in organic and perovskite solar cells where selective contacts that are able to efficiently collect majority carriers, simultaneously blocking minority carriers, are desired. Despite the vast progress made, a comprehensive understanding, needed for developing new electrode materials to improve and optimize device performance is still lacking.
A key parameter for obtaining information about processes taking place at the contacts is the effective surface recombination velocity. However, means to quantitatively measure surface recombination velocities at contact interfaces in sandwich-type thin-film devices based on organic semiconductors are lacking.
The Charge Extraction by a Linearly Increasing Voltage (CELIV) technique is one of the most common methods to measure the charge transport properties in organic semiconductor devices. In this work, we show how CELIV can be used to determine surface recombination velocities at selective and/or blocking contacts in thin-film devices. The analytical framework behind the method is presented, and confirmed by numerical drift-diffusion simulations. We furthermore demonstrate the method on organic semiconductor devices, employing TiO2 and SiO2 as cathode buffer layers. The method allows for an increased understanding of contact properties in sandwich-type thin-film devices based on organic semiconductors.
 O. J. Sandberg, A. Sundqvist, M. Nyman, and R. Österbacka, Phys. Rev. Appl. 5, 044005 (2016).
Oskar J. Sandberg, Mathias Nyman, Staffan Dahlström, and Ronald Österbacka, "Estimating the surface recombination velocity at contacts in organic devices using charge extraction by linearly increasing voltage (Conference Presentation)," Proc. SPIE 10363, Organic, Hybrid, and Perovskite Photovoltaics XVIII, 1036316 (Presented at SPIE Organic Photonics + Electronics: August 10, 2017; Published: 19 September 2017); https://doi.org/10.1117/12.2273999.5581122033001.
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