Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 46: Organic Photovoltaics I

HL 46.10: Vortrag

Mittwoch, 16. März 2011, 12:45–13:00, FOE Anorg

Determination of the built-in voltage of BHJ solar cells by temperature dependent photocurrent measurements — •Markus Mingebach¹, Carsten Deibel¹, and Vladimir Dyakonov^1,2 — ¹Experimental Physics VI, Physical Institute, Julius-Maximilians-University of Würzburg, Am Hubland, D-97074 Würzburg — ²Bavarian Center of Applied Energy Research (ZAE Bayern e. V.), Am Hubland, D-97074 Würzburg

Despite all progresses in the performance of organic BHJ solar cells (up to 8% power conversion efficiency) some very important properties such as the voltage dependent photocurrent or the built-in potential are not fully understood yet. We investigate poly(3-hexyl thiophene) (P3HT) : [6,6]-phenyl-C₆₁ butyric acid methyl ester (PCBM) solar cells by means of temperature dependent pulsed photocurrent measurements and impedance spectroscopy. We find a point of optimal symmetry (POS) that represents the case of quasi flat bands (QFB) in the bulk of the cell, which is lower than the built-in voltage. [1] This difference is due to band bending at the contacts, which is reduced at lower temperatures. Therefore we can identify the built-in voltage by measuring the POS (confirmed by temperature dependent current voltage measurements). This leads to the conclusion that the potential determined by Mott-Schottky analysis is not the built-in potential.

[1] M. Limpinsel, A. Wagenpfahl, M. Mingebach, C. Deibel and V. Dyakonov, Phys. Rev. B 81, 085203 (2010).