Recent advances in the design of dopant-free hole transporting materials for highly efficient perovskite solar cells

Continuous success has been achieved for solution-processed inorganic-organic hybrid perovskite solar cells (PVSCs) in the past several years, in which organic charge transporting materials play an important role. At present, most of the commonly used hole-transporting materials (HTMs) such as spiro-OMeTAD derivatives for PVSCs require additional chemical doping process to ensure sufficient conductivity and shift the Fermi level towards the HOMO level for efficient hole transport and collection. However, this doping process not only increases the complexity and cost of device fabrication, but also decreases the device stability. Thus development of efficient dopant-free HTMs for PVSCs is highly desirable and remains as a major challenge in this field. In this review, we will summarize the recent advances in the molecular design of dopant-free HTMs for PVSCs. (C) 2018 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.