This study presents a method to achieve high-aspect-ratio crystalline grain growth in organolead trihalide perovskite (OTP) films using non-wetting hole transport layers (HTLs), leading to efficient hybrid perovskite solar cells. The method suppresses heterogeneous nucleation and reduces drag force during grain growth, resulting in larger grain sizes and reduced grain boundary areas. This leads to improved crystallinity and reduced charge recombination in OTP thin films, achieving a high stabilized device efficiency of 18.3% in low-temperature-processed planar-heterojunction OTP devices under 1 sun illumination. The mechanism involves a two-step thermal annealing-assisted interdiffusion process that forms continuous and pinhole-free OTP films. The grain growth on non-wetting HTLs is facilitated by reduced surface tension dragging force, enabling larger grain growth and higher grain boundary mobility. The study demonstrates that the grain aspect ratio significantly impacts device performance, with larger grains leading to higher efficiency. The use of non-wetting HTLs such as c-OTPD and PTAA results in lower trap density and improved crystallinity, enhancing the performance of OTP solar cells. The work also shows that the non-wetting HTLs can significantly reduce charge recombination and improve the charge diffusion length, leading to higher device efficiency. The study highlights the importance of grain morphology in the performance of OTP solar cells and provides a simple method to achieve high-quality perovskite polycrystalline thin films with improved optoelectronic properties. The findings have potential applications in other optoelectronic devices due to the enhanced performance achieved through the improved OTP morphology.This study presents a method to achieve high-aspect-ratio crystalline grain growth in organolead trihalide perovskite (OTP) films using non-wetting hole transport layers (HTLs), leading to efficient hybrid perovskite solar cells. The method suppresses heterogeneous nucleation and reduces drag force during grain growth, resulting in larger grain sizes and reduced grain boundary areas. This leads to improved crystallinity and reduced charge recombination in OTP thin films, achieving a high stabilized device efficiency of 18.3% in low-temperature-processed planar-heterojunction OTP devices under 1 sun illumination. The mechanism involves a two-step thermal annealing-assisted interdiffusion process that forms continuous and pinhole-free OTP films. The grain growth on non-wetting HTLs is facilitated by reduced surface tension dragging force, enabling larger grain growth and higher grain boundary mobility. The study demonstrates that the grain aspect ratio significantly impacts device performance, with larger grains leading to higher efficiency. The use of non-wetting HTLs such as c-OTPD and PTAA results in lower trap density and improved crystallinity, enhancing the performance of OTP solar cells. The work also shows that the non-wetting HTLs can significantly reduce charge recombination and improve the charge diffusion length, leading to higher device efficiency. The study highlights the importance of grain morphology in the performance of OTP solar cells and provides a simple method to achieve high-quality perovskite polycrystalline thin films with improved optoelectronic properties. The findings have potential applications in other optoelectronic devices due to the enhanced performance achieved through the improved OTP morphology.