• Energy Research

Abstract We propose a novel transparent electrode consisting of silver (Ag)–aluminum doped zinc oxide (AZO)–nickel (Ni) deposited at room temperature on glass and polyethylene terephthalate (PET) for flexible organic photovoltaics. The electrode combines the high electrical conductivity and mechanical ductility of Ag, the transparency and antireflection of AZO and the high work function and stability of Ni. Environmental stability results confirmed that the electrode maintains its optical and electrical properties at both elevated temperature (500 °C) and under damp heat conditions (85 °C and 85% relative humidity). To demonstrate its functional potential, the electrode has been used as the transparent anode in an organic solar cell (OSC), which shows an efficiency of 2.6%, very close to the value (2.9%) obtained in a similar cell using the widely used indium tin oxide (ITO). With respect to ITO, the proposed transparent electrode has several advantages, including mechanical flexibility, room temperature processing and low cost.

Abstract We report a novel transparent electrode structure made of Ag–Ni bilayer on polyethylene terephtalate (PET) substrates. However, without any adequate countermeasure, such an ultrathin layer would uninvitedly oxidize even at ambient conditions due to permeation of moisture and oxygen through the polymer substrates. A combination of heat and Ar plasma pretreatment was found to significantly increase the stability of the metals layers deposited onto polymer substrates. The 1 nm Ni capping layer provides higher work function together with stability to the underlying Ag conducting layer over time and in harsh conditions of 85 °C and 85% relative humidity. The obtained Ag–Ni bilayer ultrathin films show average transparency of 75% in the visible region and sheet resistance of 11 Ω/sq. To demonstrate its operational potential, the electrode has been used as the transparent anode in an organic solar cell (OSC), which shows an overall photon conversion efficiency of >90% of the indium tin oxide (ITO) based cell which was measured to be 2.67%. With respect to ITO, the proposed transparent electrode has several advantages, including mechanical flexibility, room temperature processing and low cost.

Abstract The optical transmission of single metal thin films is usually wavelength dependent, due to plasma formation as well as intraband electronic transitions. In this paper we show that alloys can present a much smoother wavelength optical response, as it is the case of films containing 50% of Cu and 50% of Ag deposited on a transparent substrate. The optimized optical transparency and electrical resistance properties of the ultrathin alloy film (10 nm), combined with the high work function and environmental stability provided by a Ni capping layer, have allowed achieving organic photovoltaic cells almost as efficient as those incorporating indium tin oxide (ITO), which is the most widely used transparent electrode. Compared to ITO, the proposed structures are more compatible with organic materials and mechanically ductile, and less expensive, making them ideal for flexible optoelectronic devices produced by roll-to-roll techniques.

Abstract We demonstrate an indium-free organic photovoltaic cell that incorporates an ultrathin metal film as a semitransparent anode. In the proposed device structure, the indium tin oxide electrode is replaced by an ultrathin Cu–Ni bilayer. When an NiO is used as the hole transporting layer, the characteristic photovoltaic parameters of the cell fabricated with the metal electrode are similar to those of the device fabricated with the indium tin oxide (ITO). Despite the fact that the metal electrode exhibits a transparency that is 65% of the ITO electrode, the short-circuit current for the metallic anode based cell is 77% of the ITO based one, indicating that the photon absorption could be enhanced by the optical microcavity formed between the Cu–Ni and Al electrodes. The overall photo-conversion efficiency for the metallic electrode based cell is 76% of the ITO based one, which was measured to be 3.3%. The obtained performances of ultrathin metals when included in the cell architecture used here, combined with their low cost, high compatibility with other materials, and mechanical flexibility, confirm their potentials for organic photovoltaics.

Corrigendum to ‘Highly stable Ag–Ni based transparent electrodes on PET substrates for flexible organic solar cells’ [Solar Energy Materials and Solar Cells 107 (2012) 63–68] Nadia Formica , Dhriti Sundar Ghosh , Tong Lai Chen , Christian Eickhoff , Ingmar Bruder , Valerio Pruneri a,c a ICFO, Institut de Ciences Fotoniques, Mediterranean Technology Park, Av. Carl Friedrich Gauss 3, 08860 Castelldefels (Barcelona), Spain b BASF SE, Carl-Bosch-Strasse 38, 67056 Ludwigshafen, Germany c ICREA, Institucio Catalana de Ricerca i Estudis Avanc-ats, 08010 Barcelona, Spain