Researchers from the Chinese Academy of Sciences have designed perovskite solar cells with power conversion efficiency of 18.1% by adding Titanium (Ti) cathode layer.
Two different device configurations including n-i-p and p-i-n have been adopted for fabricating the PSCs. As organic electron transport layers (ETLs), fullerene and its derivatives (C60 and PCBM) play an important role in efficient PSCs with p-i-n structure (ITO/Hole transport layers/perovskite/ETLs/Cathode). However, the cathode metal atoms diffuse through the organic ETLs to the perovskite layer, causing degradation of PSCs. Also, the instability and high-cost of organic ETLs were limiting factors for the commercialization of PSCs. Considering these problems, the research team led by Dr. LI Xinhua, developed the ultra-thin Ti cathode interlayer to replace organic ETLs for fabricating efficient and low-cost PSCs.
The Ti-N bond between MAPbI3 and Ti was able to passivate the surface traps and suppress surface decomposition of the MAPbI3 film. Owing to low diffusion coefficient of Ti, the diffusion of Au was also suppressed in the PSCs with Ti interlayer.
Furthermore, after the incorporation of the Ti interlayer, the PCE increased substantially for both Au and Cu electrodes, although the work function of Cu (-4.3eV) and Au (-5.1eV) were very different.