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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices

SYOE 8: Poster Session SYOE

SYOE 8.52: Poster

Dienstag, 27. März 2007, 18:00–20:00, Poster B

Utilization of pentacene as a photoactivator and an exciton transporter in organic solar cells — •Ziruo Hong, Bert Maennig, Martin Pfeiffer, and Karl Leo — Institut für Angewandte Photophysik, Technische Universität Dresden, Dresden, Germany

Power conversion efficiency (ηE) of organic solar cells based on pentacene/C60 heterojunctions is mainly limited by open circuit voltage (Voc), although the extremely long exciton diffusion length (LD) of pentacene among organics is of advantage for solar cell applications.

In this work, pentacene/zinc phthalocyanine (ZnPc)/C60 multi-heterojunctions were introduced to increase Voc. Here, Voc is dominated by ZnPc/C60 interface. Excitons in pentacene layer diffuse into ZnPc layer via energy transfer, and contribute to photocurrent. Thus ηE was improved. According to quenching effect of ZnPc on luminescence from pentacene, exciton diffusion from pentacene to ZnPc was determined by efficiency of pentacene-to-ZnPc energy transfer, not LD.

Currently, we are seeking possibility of taking advantage of long LD and high hole mobility in pentacene films, to overcome two of critical shortcomings of organic solar cell materials, namely short LD and low charge carrier mobilities, by imbedding organic nanoclusters in pentacene films. The only role that the nanoclusters play pentacene matrix is as a sensitizer, i.e. transferring photon energy they absorb to pentacene, and the rest part of the photovoltaics is as same as pentacene based heterojunctions. Therefore, the limitation of short LD and low hole mobilities of some organic absorbers can be removed. The related experiment is being carried out.