A dopant-free hole-transporting material for efficient and stable perovskite solar cells†
An efficient pristine hole-transporting material (HTM), tetrathiafulvalene derivative (TTF-1), was introduced into perovskite solar cells, without the use of p-type dopants. As compared to cells based on well-known p-type doping with spiro-OMeTAD, perovskite solar cells based on dopant-free TTF-1 performed with a comparable efficiency of 11.03%; moreover, the stability of the dopant-free TTF-1 based cell was greatly improved two fold in air at a relative humidity of ∼40%. To the best of our knowledge, this is the first case of perovskite solar cells employing a dopant-free HTM based on a tetrathiafulvalene derivative yielding an efficiency over 11%. The present finding paves the way for the development of efficient dopant-free HTMs for perovskite solar cells, which promotes the advancement of cost-effective and practical perovskite solar cells.