Important Role of Additive in Morphology of Stretchable Electrode for Highly Intrinsically Stable Organic Photovoltaics
Eul‐Yong Shin, So Hyun Park, Yeonjee Jeon, Kyuyeon Kim, Giseok Lee, Jung‐Yong Lee, Hae Jung Son
Abstract
Developing intrinsically stretchable organic photovoltaics (IS-OPVs) is crucial for serving as power sources in future portable and wearable electronics. PEDOT:PSS is most commonly used to prepare highly conductive, transparent electrodes with high stretchability. The mechanical properties of PEDOT:PSS films are significantly affected by their morphology, which is primarily determined by the processing additives used. We investigate the effects of two additives, poly(ethylene glycol) (PEG) and (3-glycidyloxypropyl)trimethoxysilane (GOPS), on the stretchability of the electrode. The PEG additive forms hydrogen bonds with sulfonyl groups of PSS without significant interaction among itself, which releases mechanical stress in the PSS-rich region of the PEDOT:PSS films. On the other hand, the GOPS additive not only forms hydrogen bonds with PSS but also undergoes a chemical reaction to create a cross-linked structure within the film, which effectively enhances the stretchable properties of the PEDOT:PSS film. In addition, the GOPS promotes a more hydrophilic surface compared to PEG, resulting in improved adhesion to the upper layer in IS-OPV devices. This improves the stretchability of IS-OPV devices, as well as their solar cell performance. We demonstrate IS-OPVs that are prepared using GOPS by a non-spin-coating method and these devices exhibit higher performance compared with PEG-based counterparts. Furthermore, the GOPS based IS-OPV shows significantly improved mechanical stability, enabling it to retain 90% of its initial efficiency when subjected to 20% strain.