Control of aggregation and dissolution of small molecules hole transport layer through a doping strategy of highly efficient perovskite solar cell

摘要： Recently, small molecule hole transporting materials (HTLs) have attracted growing interest in perovskite solar cells due to their low-cost, excellent stability and better energy level alignment with perovskite. Nonetheless, an amorphous and coarse surface film is one of the main obstructions to the performance of these small molecule HTLs. Herein, N,N′-Di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) small molecule was doped with a polymer to overcome the formation of molecular aggregation in HTL. This polymer doping strategy resulted into a very smooth surface, which improved photo-physical and electrochemical properties at HTL/perovskite interface. Consequently, a maximum power conversion efficiency (PCE) of 17.80%, 32% higher than the control, i.e. NPB-based device (13.57%), has been achieved. This work reveals critical behaviour of molecular aggregations on the performance of perovskite solar cells, which impairs the development of an efficient device based on small molecule HTLs.