Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
Publication date: 20th April 2022
Despite extensive research efforts on optimizing materials and devices of non-fullerene acceptor (NFA) organic solar cells toward high efficiency, ensuring long-term stability of these high-efficiency devices is equally important yet remains challenging for this promising technology. For OSCs operating under real-world conditions, a range of different extrinsic factors (including light, heat, oxygen and humidity) affect the materials, BHJ blends and interfacial contacts, resulting in quick device degradation. It has been demonstrated that the photo-oxidation in NFAs occurs by superoxide radical ion formation which is connected to the energetics of the electron acceptors [1]. Studies on physical dynamics of devices show the NFA photo-oxidation which acts as trap states in ambient exposed blends hampers device performance [2].
Although, these studies come in handy in understanding the degradation mechanisms of certain materials, these photo-oxidation investigations are mainly based on active layers deposited under carefully controlled aging conditions, e.g., dry air and 1 Sun exposure. In reality, for fully ambient large-scale roll processing of OSCs, all the layers are deposited in air and exposed to room light until consequential deposition of remaining layers.
Herein, we focus on the comparison of inert and ambient processing of active layers. We investigate light and air induced degradation trend difference in ambient and inert deposition for polymer:fullerene and polymer:NFA OSC systems. It is known that there is a loss of performance when active layer is deposited in ambient compared to inert conditions. We show that deposition conditions which are close to industrial processing, such as coating in ambient and exposure of the active layer blends to air for a short time results in a significant loss of device performance compared to inert processing conditions.
Our ongoing work highlights the importance of film deposition conditions and ambient exposure time in performance and stability of OSCs, paving the way towards OSCs with high efficiency and long-term operation stability.
Financial support from Swedish Foundation for Strategic Research (SSF) is greatfully acknowledged.