Charge carrier mobility and lifetime of organic bulk heterojunctions analyzed by impedance spectroscopy

✍ Scribed by Germà Garcia-Belmonte; Antoni Munar; Eva M. Barea; Juan Bisquert; Irati Ugarte; Roberto Pacios

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 343 KB
• Volume: 9
• Category: Article
• ISSN: 1566-1199
• DOI: 10.1016/j.orgel.2008.06.007

✦ Synopsis

Charge carrier diffusion and recombination in an absorber blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C 61 -butyric acid methyl ester (PCBM) with indium tin oxide (ITO) and aluminium contacts have been analyzed in the dark by means of impedance spectroscopy. Reverse bias capacitance exhibits Mott-Schottky-like behavior indicating the formation of a Schottky junction (band bending) at the P3H:PCBM-Al contact. Impedance measurements show that minority carrier (electrons) diffuse out of the P3HT:PCBM-Al depletion zone and their accumulation contributes to the capacitive response at forward bias. A diffusion-recombination impedance model accounting for the mobility and lifetime parameters is outlined. Electron mobility results to be 2 Â 10 À3 cm 2 V À1 s À1 and lifetime lies within the milliseconds timescale.