Magnetophotocurrent effect in organic photovoltaic cells at low temperatures

The photocurrent responses were investigated for the bulk-hetero-junction of poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-1-phenyl-(6,6)C61 (PCBM) (1), and the single-active-layer junction of (5,10,15,20-tetraphenyl porphyrinato)zinc (II) (Zn(TPP)) (2), in the temperature range between 300 K and 1.5 K under the magnetic field up to 8 T. Magnetic field effect (MFE) of the photocurrent was observed in both devices. In the device (1), MFE at low temperatures was small for the continuous light illumination, but remarkable for the chopped-light illumination. An experiment of photoinduced charge extraction by linearly increasing voltage (photo-CELIV) revealed a drastic increase in the lifetime for trapped carriers under applied magnetic field. In the device (2), the photocurrent decrease under magnetic field was observed both for the continuous-light and the chopped-light illumination.