We used hexylamine (CH3(CH2)4CH2NH2, HA) for a quasi-2D HA(CH3NH3)n−1PbnI3n+1 (n = 1, 2, 3, and 4) perovskite, which had sufficient long alkyl chains to maintain the chemical stability of the perovskite and exhibited an appropriate band gap for application to solar cells as a light absorber.