Fabrication of CH3NH3PbI3 perovskite-based solar cells: Developing various new solvents for CuSCN hole transport material

- New solvents were successfully developed for CuSCN to increasing solubility.
- Mixture of (Propylsulfide + Isopropanol + MAI) solvent identified as the best solvent for CuSCN HTM.
- High power conversion efficiency achieved for the newly developed solvent.

Copper (I) thiocyanate (CuSCN) is a cost-competitive hole selective contact for the emerging organic-inorganic hybrid perovskite solar cells. However, limitation of solvent is the main issue for getting an optimal thickness for pin-hole free selective contacts. We have developed various solvents such as mixture of propylsulfide with chlorobenzene (1:1), isopropanol with methylammonium iodide (10 mg/ml) and propylsulfide + isopropanol (1:2) + MAI (10 mg/ml) for dissolving CuSCN. It was found that perovskite layer was more stable once CuSCN coating laid on the top surface using the propylsulfide + isopropanol (1:2) + MAI (10 mg/ml) solvent than conventional propylsulfide by doctor blade technique. By employing low temperature solution-process techniques, power conversion achieved over 10% under full sun illumination by the proposed mixed solvent. CuSCN continues to offer promise as a chemically stable and straightforward replacement for the commonly used expensive organic hole conductor (2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene (Spiro-OMeTAD)).