Dresden 2017 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 33: Organic Photovoltaics and Electronics I (joint session CPP/DS/HL, organized by HL)

CPP 33.9: Talk

Wednesday, March 22, 2017, 12:00–12:15, POT 81

Low Voltage Losses in Cascade Organic Solar Cells by Reducing the Donor-Acceptor Interfacial Area — •Vasileios Christos Nikolis, Johannes Benduhn, Felix Holzmüller, Christian Körner, Donato Spoltore, and Koen Vandewal — Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP), Technische Universität Dresden, Germany

High photon energy losses (E_loss) significantly limit the open-circuit voltage (V_OC) and power conversion efficiency (PCE) of organic solar cells (OSC). Reduction of E_loss, while keeping a high charge generation yield, can lead OSC into a new, beyond 12%, PCE regime.

In this work, we present an optimization route, which increases V_OC by reducing the interfacial area between electron donor (D) and acceptor (A) in planar heterojunction solar cells. Through an introduction of thin and discontinuous interlayers between D and A, we increase the V_OC of a cascade organic solar cell from 0.98 V to 1.16 V. Although the V_OC maximizes at the expense of short-circuit current and fill factor for thick interlayers, an optimum interlayer thickness for increased PCE exists. By appropriately measuring the optical gap (E_opt) of the device at 1.73 eV, the obtained E_opt-qV_OC losses of 0.57 eV are among the lowest observed for organic photovoltaics. Most importantly, for these devices, the external quantum efficiency (EQE) peak at the edge of the spectrum (705 nm) remains high and reaches 79%.

Our work shows that low energy losses for strongly absorbed photons can be combined with a high EQE in organic photovoltaic devices.