Silane or Siloxane-Side-Chain Engineering of Photovoltaic Materials for Organic Solar Cells

With the tactful material design, skillful device engineering, and in-depth understanding of morphology optimization, organic solar cells (OSCs) have achieved considerable success. Therefore, OSCs have reached high power conversion efficiencies (PCEs) exceeding 19%. Especially, continuously emerging new materials have been considered as one of the key factors to improve the PCEs of OSCs. Among molecular design strategies, side-chain engineering is an easy and commonly-used means which can optimize the solubility, alter intermolecular stacking arrangement, fine-tune the open circuit voltage (VOC), thus ultimately improve the performance. As hybrid side chains, silane and siloxane side chains have considerable effects, not only in increasing the carrier mobility and tuning the energy level, but also in affecting the crystallinity and molecular orientation. In this review, the latest developments in photovoltaic materials based on silane and siloxane side chains are presented to illustrate the structure-property relationships. The review comprehensively includes silane-side based polymer/small molecule donors; siloxane-side based polymer/small molecule donors, and polymer/small molecule acceptors. Then the similarities and differences between these two side chains are demonstrated. Finally, the possible applications and future prospects of silane and siloxane side chains are presented.