  Organometal trihalide perovskite solar cells have been rapidly developed and
attracted much attention in recent years due to their high photoelectric
conversion efficiency and low cost. Pulsed laser deposition (PLD) is a widely
adopted technology which is used in the preparation of thin films, especially
oxide thin films. With this technology, the thickness and composition of films
can be conveniently and accurately controlled. In the structure of perovskite
solar cells, TiO$_2$ layer working as the n-type semiconductor is used to block
holes and transport electrons into electrode, which is crucial for the
performance of whole devices. We introduced the PLD technique into preparation
of TiO$_2$ layer. In comparison with common spin coating method, TiO$_2$ layer
prepared by this technique is ultrathin and more compact. Compact TiO$_2$
(c-TiO$_2$) layers with optimized thickness of 32 nm have been prepared by the
PLD method and the highest efficiency of 13.95 % for the MAPbI$_3$-based solar
cell devices has been achieved.
