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 (C61(CO2Et)2) 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:C61(CO2Et)2: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 ~10-6 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

Electrodes for GaOHPc:PCBM Bulk Hetrojunction Solar Cell

The bulk heterojunction approach appears to be one of the most promising concepts of creating efficient, low cost and easily producible organic solar cells. For this purpose one of the best materials was regioregular poly-3-hexylthiophene (P3HT), which is widely used as a donor molecule and a hole transporter, with soluble fullerene derivative (PCBM) as an acceptor and electron transporter. The main drawback of this highly efficient blend is its limited spectral range, covering only a 350–650nm spectral interval. So the main aim of the present work was to extend the spectral range of the cell up to 850nm by adding a second bulk heterojunction layer of complementary absorption spectrum to the P3HT:PCBM layer. Therefore hydroxygallium phthalocyanine (GaOHPc) and PCBM blend was used as an additional layer because GaOHPc has strong and wide intermolecular charge transfer (CT) absorption band of around 830–850nm. Thus an organic bi-layer bulk heterojunction system GaOHPc:PCBM/P3HT:PCBM has been built by the spin coating technique having high charge carrier photogeneration efficiency in the 350–850nm spectral range. The cell annealing temperature influence on the cell performance has been investigated in a 10−6 mbar vacuum within the temperature range from 30°C to 100°C. It was found that annealing at 100°C increases the short-circuit photocurrent external quantum efficiency (EQE) values more than 2 times. Various top electrodes of Al, In and Yb/Al/Se were examined to achieve the best performance of our bi-layer cell. It was found that the best power conversion efficiency (PCE) is provided by an Yb/Al electrode covered with a protective Se layer