Silver Nanowire Composite Electrode Enabling Highly Flexible, Robust Organic Photovoltaics

Using Ag nanowires (NWs) is a promising approach to make flexible and transparent conducting electrodes for organic photovoltaics (OPVs). However, the roughness of the NWs can decrease device performance. Herein, a Ag NW electrode embedded in a UV-curable epoxy that uses a simple mechanical lift-off process resulting in highly planar electrodes is demonstrated. A bimodal blend of Ag NWs with varying aspect ratios is used to optimize the transparency and conductivity of the electrode. In addition, a ZnO layer is coated on the Ag NWs prior to the embedding process to ensure low contact resistance in the OPV cells. The resulting resin-embedded ZnO-encapsulated silver nanowire (REZEN) electrode is found to have excellent mechanical stability. REZEN electrode-based OPV cells exhibit comparable performance with reference devices, achieving maximum power conversion efficiency (PCE) of 13.5% and 13.6% respectively. The REZEN-based OPV cells are also mechanically robust, retaining 97% of their PCE after 5000 cycles at R = 1.2 mm and 94% PCE after 1000 cycles at R = 0.55 mm. This flexibility is among the highest reported for freestanding devices. Thus, the REZEN electrode is a promising and simple strategy to achieve mechanically robust ITO-free flexible OPV cells.

Automated summary

This study demonstrates a promising and simple strategy using silver nanowires (NWs) embedded in UV-curable epoxy to achieve mechanically robust and ITO-free flexible organic photovoltaics (OPVs). The resulting resin-embedded ZnO-encapsulated silver nanowire (REZEN) electrode exhibits highly planar surfaces and excellent mechanical stability. OPV cells based on the REZEN electrode show comparable performance with reference devices and retain high efficiency even after multiple cycles, making them highly flexible and durable.