Investigation of recombination processes in bulk-heterojunction organic solar cell by extraction of injected charge carriers

Abstract

In this paper, we used extraction of injected charge carriers technique and time-of-flight method to establish recombination rate dependency on carrier concentration and thickness in a bulk-heterojunction organic solar cell with the active layer blend consisting of poly(3-hexylthiophen-2,5-diyl) and [6,6]-phenyl-C61-butyric acid methyl ester (P3HT: PCBM). Using aforementioned techniques and numerical calculations, we determined that 1.8-diiodiooctane processing additive in combination with chlorobenzene solvent in solution-processed P3HT: PCBM samples causes charge carrier transport and recombination rate changes with increasing device thickness. Also, recombination velocities of P3HT: PCBM blends obtained with the extraction of injected charge carriers technique have a two-component dependency on charge carrier concentration governed by interfacial states between two pure phases.