Silver Nanowire Back Electrode Stabilized with Graphene Oxide Encapsulation for Inverted Semitransparent Organic Solar Cells with Longer Lifetime

Semitransparent organic solar cells (ST-OSCs) have garnered strong interest for building integrated photovoltaics (PV) and wearable electronics. Although seen as an appealing low-cost PV technology, OSCs suffer from high instability against moisture and gas, which limits their widespread commercialization. A method is proposed to increase significantly the lifetime of inverted ST-OSCs by encapsulating a silver nanowire (AgNW)-based anode with graphene oxide (GO). AgNWs are covered with a GO layer on both sides leading to a sandwich-like structure using only scalable and solution-compatible processes. On one side of the AgNW network, an ultrathin GO layer allows for protecting the AgNWs from the acidic poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) hole transport layer (HTL) underneath without jeopardizing the device energy level alignment and the Ohmic contact between the HTL and the AgNWs. On the other side, a thicker GO layer at the top aims to prevent the AgNWs from degradation because of atmospheric sulfidation. Such double-sided GO encapsulation offers efficient protection to both the AgNW network and the entire device stack. A fivefold increase in the overall device lifetime without additional encapsulation is demonstrated. Cross-linking the PEDOT:PSS layer with (3-glycidyloxypropyl)trimethoxysilane is also found to be essential to preserve the PEDOT:PSS integrity during device fabrication and achieve high fill factors.