Effective Control of Crystal Grain Size in FA0.9Cs0.1PbI3
(FA: Hc(Nh)2) Perovskite Solar Cells with a Pseudohalide Pb(SCN)2 Additive
Ming-Wei Lin1*, Hung-Wei Shiu1, Ming-Hsien Li2, Peter Chen2, Takuji Ohigashi3, Nobuhiro Kosugi3, Yao-Jane Hsu1
1Nano science group, National synchrotron radiation research center, Hsinchu, Taiwan
2Department of photonics, National cheng kung university, Tainan, Taiwan
3UVSOR Synchrotron, Institute for Molecular Science, Okazaki, Japan
* presenting author:mingwei lin, email:mingwelin18@gmail.com
In this report, lead(II) Thiocyanate (Pb(SCN)2) was
 used as a dopant in a FA0.9Cs0.1PbI3
 (FA: HC(NH)2) framework, aiming for its use as an absorber layer for photovoltaic
applications. Photovoltaic performances are evaluated with detailed materials characterizations. Scanning electron microscopy (SEM) images show that Pb(SCN)2-based perovskite films have long-range uniform morphology and large grain sizes up to 1 μm. The morphology variation caused by Pb(SCN)2 is also clear seen by Scanning transmission X-ray microscopy (STXM). The X-ray photoemission spectra (XPS) was employed to observe the characteristic peaks for both Pb(SCN)2-based and pure FA0.9Cs0.1PbI3 perovskite. We observed that only a small amount of S remained in the film, that is, the Pb(SCN)2 film transformed to PbI2 before the formation of perovskite film. In summary, we fabricated SCN-based perovskite solar cells and achieved a power conversion efficiency of 15.1 %, the efficiencies of 9.1% for perovskite solar cells with no Pb(SCN)2. It is worth noting that the price of Pb(SCN)2 is only 4 % of PbI2. These results demonstrate that pseudo-halide perovskites are promising materials for fabricating low-cost perovskite solar cells.

Keywords: FA0.9Cs0.1PbI3
 (FA: HC(NH)2), Pb(SCN)2, perovskite, grain size, high efficiency