Satoshi Uchida1,Hiroshi Segawa1
The University of Tokyo1
Satoshi Uchida1,Hiroshi Segawa1
The University of Tokyo1
Recently, perovskite solar cells have become the latest research field among various new generation photovoltaic technologies due to their high performance and potentially low-cost production. The power conversion efficiency has already reached over 25% in 2020 much beyond another solar cells such as CIGS or amorphous Si. The further performance still looks promising toward the Shockley–Queisser limit at around 30%. For that purpose, physical chemistry understanding based on the crystallography must be essential to design the good light harvesting, good charge separation and good charge transfer.<br/><br/>Recently we reported the scientific revelation that the crystal phase of thin film CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> consists of the mixture of tetragonal phase and cubic phase. Moreover, bold zebra pattern with d-spacing with 14.2Å (2θ=6.22° for CuKα by XRD) was clearly observed by high resolution TEM with FIB processing that consists with tetragonal and cubic phase superlattice. The typical high magnification In the TEM observation characteristic identity of perovskite can be seen as (1) Phase coexistence (2) Superlattice (3) Nano size domain (10~20nm).<br/><br/>To make more high performance as a solar cell, the crystal phase control with liquid nitrogen quenching just after the hot plate heating was newly examined. The resulting cell performance was impressive, about 2% more than that without Liq. N<sub>2</sub> treatment. Details on TEM observations are also provided for such procedures.