Hole transport layer (HTL) plays a critical role for achieving high performance solution-processed optoelectronics including organic electronics. For organic solar cells (OSCs), the inverted structure has been widely adopted to achieve prolonged stability. However, there are limited studies of p-type inorganic semiconductor-based effective HTL on top of organic active layer (hereafter named as top HTL) for inverted OSCs. Currently, the p-type top HTLs are mainly two-dimensional (2D) materials, which have vertical conduction limitation intrinsically and is too thin to function as practical HTL for large area optoelectronic applications. Here, we demonstrate a novel self-assembled quasi three-dimensional (3D) nanocomposite as a p-type top HTL . Remarkably, the novel HTL achieves ~15 times enhanced conductivity and ~16 times extended thickness compared to the 2D counterpart. By applying this novel HTL in inverted OSCs covering fullerene and non-fullerene systems, device performance is significantly improved. The champion power conversion efficiency (PCE) reaches 12.13%, which is the highest reported performance of solution processed HTL based inverted OSCs. Furthermore, the stability of OSCs is dramatically enhanced compared with conventional devices. The work contributes to not only evolving the highly stable and large scale OSCs for practical applications but also diversifying the strategies to improve device performance.
 J. Cheng, H. Zhang, Y. Zhao, J. Mao, C. Li, S. Zhang, K.S. Wong, J. Hou, W.C. H. Choy, "Self-assembled Quasi-3D Nanocomposite: A Novel p-Type Hole Transport Layer for High Performance Inverted Organic Solar Cells", Adv Funct. Mater., DOI:10.1002/adfm.201706403.