All-sputtered contacts for organic solar cells

Organic solar cells are usually contacted with a thermally evaporated aluminium cathode while the sputter deposition technique is conventionally avoided despite some technological advantages, because of potential damage to the organic absorber layer. We report that a thin LiCoO2 interlayer, although sputtered itself, can reduce this damage and advantageously influence the contact formation and cell performance similar to a LiF interlayer. However, these devices require an additional post-annealing step. An all-sputtered LiCoO2/Al cathode is thereby possible with cell efficiencies comparable to those of cells with conventionally evaporated LiF/Al. Sputter-deposited cathode layers are especially important when transparent conductive contacts are desired on top of an organic absorber layer. We demonstrate semitransparent cells with power conversion efficiencies well above 3% with sputtered transparent cathodes containing LiCoO2 interlayers. (c) 2007 Elsevier B.V. All rights reserved.