Ionically Gated Hybrid Tandem Organic Photovoltaics*

In our work, `Electrochemically gated organic photovoltaics with tunable carbon nanotube electrodes', recently published in Applied Physics Letters, and our previous APS presentation, we demonstrated a hybrid device comprised of an organic photovoltaic (OPV) monolithically attached to a supercapacitor via a common transparent carbon nanotube (CNT) electrode. This structure may also be viewed as an electrochemically gated OPV in which the gate voltage gradually shifts a resistor-like device into a high efficiency photovoltaic. We have extended this concept to an electrochemically-gated, parallel tandem, organic photovoltaic device, which features two photoactive layers in addition to the supercapacitive cell. This device can be produced entirely in ambient conditions via spin-coating and lamination, and avoids many processing difficulties associated with tandem architectures. Additionally, this architecture allows us to perform experiments to better understand the undelaying phenomena in this system such as whether the electrochemical charging in the OPV device extends to the semiconducting photoactive layers or is constrained entirely to the carbon nanotube electrodes.