PV and magnetic field effects in poly(3-hexylthiophene)-fullerene cells doped with phthalocyanine soluble derivative

An attempt was made to widen the photosensitivity spectral range of poly(3-hexylthiophene)-fullerene blend by adding an extra electron donor - a newly synthesized soluble phthalocyanine derivative (SnClPc) having the electron absorption band at 708 nm. As the electron acceptor, home-synthesised di(ethoxycarbonyl) methano-fullerene carboxylate (C(COEt) was used, and as the hole transporter - the regioregular poly 3-hexylthiophene (P3HT). The sandwich-type samples were prepared on an ITO glass substrate by coating it with a 30-50 nm thick PEDOT:PSS layer followed by a ~100 nm thick P3HT:C(COEt):SnClPc blend. For the top electrodes In or Au were used. Spectral dependences of the PV effect and of the influence of external magnetic field (0-3000 Oe) on it were studied in the 370-1000 nm spectral range in vacuum of ~10 Torr. Significant photosensitivity of the blend was observed in the 370-800 nm spectral range. However, the short-circuit photocurrent quantum efficiency evaluated for absorbed light was found to be 4 times higher for illumination in the P3HT absorption band as compared with that in the SnClPc band. The observed magnetic field effect shows that the low IPCE values may be explained by the space charge formation in the samples, leading to a strong geminate recombination of CP states.