High-performance polymer solar cells with >10% efficiency

Abstract

Polymer solar cells (PSCs) with bulky heterojunction structure have attracted considerable attention due to their advantages in making flexible, light weight and large area solar cell panels through the low cost roll-to-roll printing technologies. In the past decades, tremendous efforts have been devoted to developing new materials and device fabrication methods to improve the power conversion efficiencies (PCEs) of PSCs. In 2014, the PCEs have been boosted to ~10% for the PSCs with single junction and ~11% for the PCS with double/triple junctions. According to the reported results, the new materials and processing methods of the photovoltaic active layer in PSCs are of equal importance. In 2004, Yongfang Li and Jianhui Hou et al. at the Institute of Chemistry, Chinese Academy of Sciences (ICCAS) pioneered the concept of two dimensional -conjugation in the design and synthesis of photovoltaic polymers. The conjugated side chains could broaden the absorption spectrum and enhance the hole mobility of 2D-conjugated photovoltaic polymers. After that, they focused on the design of highly efficient photovoltaic polymers based on 2Dconjugated benzodithiophene (2D-BDT). In early 2014, Li et al. [1] first used alkylthio groups to improve photovoltaic properties of 2D-BDT-based polymers. More recently, Hou et al. [2] further modified the 2D-BDT using linear alkylthio groups. In this work, a novel photovoltaic polymer PBDT-TS1 (Figure 1) was designed and synthesized with a linear alkylthio chain staying in the state-of-the-art polymer PTB7-Th for the well balance of absorption range, molecular order and energy level. Owing to the broad spectral coverage, ordered packing and high mobility of 1×10 2