(Invited) Uniform Nanostructures for Highly Efficient and Reproducible Perovskite Solar Cells

Organo-lead trihalide perovskites (CH₃NH₃PbX₃, X = I, Br or Cl) as light absorption materials have attracted great attention recently in photovoltaic research. By virtue of their high absorptivity and long carrier diffusion length, the power conversion efficiency (PCE) was rapidly increased from 3.8% to above 17% within the short five years. In this presentation, I will report some our latest researches in this field.

Firstly, the hole-blocking layer is required to prevent holes formed in the perovskie or HTL layer from reaching the FTO electrode, which would otherwise short-circuit the cell. Optimization of the blocking layer is a key factor for improving the device performance of perovskite solar cells. We systematically examined the different blocking layer fabricated by three different methods. The surface morphology and film resistance shows that atomic layer deposition (ALD) based TiO2 compact layer contains much lower density of nano-scaled pinholes with respect to spin-coating and spray pyrolysis ones. The ALD-TiO2 layer acts as an efficient hole-blocking layer in perovskite solar cells, which offers a large shunt resistance and enables a high power conversion efficiency of 12.56%.

Secondly, uniform, highly crystalline perovskite film is important for sequential deposition processed perovskite solar cells. We develop a new method to enable an efficient deposition of perovskite film with enhanced conversion rate and surface morphology. By this approach, the energy conversion efficiency of mesoporous-free perovskite solar cells was twice as high as that of using traditional method.