Solvation of NiOfor hole transport layer deposition in perovskite solar cells

A series of nickel oxide (NiO) inks, in the perovskite antisolvent chlorobenzene (CB) containing 15% ethanol, were prepared for the fabrication of p-i-n perovskite solar cells by blade coating. The inks included triethylamine (Et₃N) and alkyl xanthate salts as ligands to disperse NiOparticle aggregates and stabilize suspension. A total of four inks were evaluated: 0X (Et₃N with no alkyl xanthate), 4X (Et₃N + potassiumn-butyl xanthate), 12X (Et₃N + potassiumn-dodecyl xanthate), and 18X (Et₃N + potassiumn-octadecyl xanthate). The inks were characterized by UV-visible spectroscopy and FT-IR spectroscopy and the resulting films analyzed by thermogravimetry and scanning electron microscopy. Devices prepared using the 0X ink resulted in a peak power conversion efficiency (PCE) of 14.47% (0.25 cm²) and 9.96% (1 cm²). The 0X devices showed no significant loss of PCE after 100 days in a nitrogen flow box. Devices prepared with inks containing alkyl xanthate ligand had lower PCE that decreased with decreasing chain length, 18X > 12X > 4X.