The growth of large-area ultrathin single-crystalline wafers of methylammonium lead bromide is investigated on a hole transport layer using a diffusion-facilitated inverse temperature crystallization method. It is shown that, in addition to the hydrophobic confining layers, optimized precursor molar ratio and growth temperature are essential for realizing large-area single-crystalline wafers of device-friendly thickness in the range of 20–30 µm. The necessity of the hydrophobic layer for the realization of large-area wafers using the space confined crystal growth method is explained from consideration of the occurrence of heterogeneous nucleation. Space-charge limited current studies of the device fabricated with the synthesized single-crystal wafer show excellent charge transport mobility of 2.12 cm2/vs and a low trap-state density of 1.34 ⋅ 1011 cm−3.