Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 5: Organic Semiconductors I: Solar Cells A (jointly with HL, DS)

CPP 5.10: Vortrag

Montag, 14. März 2011, 16:45–17:00, ZEU 222

Charge extraction with linearly increasing voltage: A numerical model for parameter extraction — •Martin Neukom, Simon Züfle, Nils Reinke, and Beat Ruhstaller — Institute of Computational Physics, Technikumstr 9, 8401 Winterthur, Switzerland

Device characterisation is an essential part in the process of improving the performance and lifetime of organic solar cells. Most of the device and material parameters are not accessible by measurements therefore sophisticated measurement techniques in combination with numerical simulations are needed to extract these parameters. A frequently used method to determine material parameters like charge carrier mobilities and the recombination coefficient is the CELIV technique (charge extraction by linearly increasing voltage). In this technique a voltage ramp is applied to the device in order to extract free charge carriers inside the bulk. With a simple analytical formula the mobility is commonly estimated on the basis of the temporal position of the current peak. We simulate the CELIV experiment, transient and steady-state measurement techniques with a fully-coupled opto-electronic model. On the one hand we investigate the limitations of the analytical formulas for mobility determination. On the other hand we use our model to fit several experimental datasets simultaneously to obtain elementary material parameters like the electron and hole mobility, recombination coefficient, photon to charge conversion efficiency and injection barriers in both printed and spin-coated bulk heterojunction solar cells. We deduce the influence of these material parameters on the overall device performance.