They have found that HTM can play a crucial role in the stability of PSC . Song Li et al. have shown that different HTMs provide different output performance and stability under different conditions . Some HTMs show a higher efficiency but can not retain stability for a long time. Additionally, some common HTMs are expensive compared to their output performance. Another common drawback of common PSC is toxicity. Most highly efficient and common PSCs contain toxic Pb. Although Pb-based PSCs are highly efficient, the toxicity of Pb can be hazardous for both human beings and the environment which is a barrier to commercialization . Hence Pbfree and highly efficient cell structure is eminent to reduce risk along with the cells.