[en] Highlights: • Electron-rich TiO₂ films are prepared via a glucose-assisted solvothermal process. • Bilayer dense/porous CH₃NH₃PbI₃ films are formed. • Efficient light harvesting and charge collection within devices realized. • Integrated planar/bulk heterojunction solar cell attains an efficiency of 17.75%. To achieve high-performing perovskite solar cells (PSCs) interfacial engineering of the perovskite thin film and charge carrier-selective layers is vital for fast extraction of photogenerated electrons and holes, and the suppression of electron-hole recombination. Herein, a glucose-assisted self-assembly solvothermal protocol is reported to prepare electron-rich TiO₂ thin films as effective electron transport layers exhibiting enhanced electron mobility. Bilayer structured CH₃NH₃PbI₃ perovskite films are spontaneously formed, consisting of a flat and dense bottom layer forming the TiO₂/CH₃NH₃PbI₃ planar heterojunction and a textured and porous top layer elongating in the vertical direction forming the CH₃NH₃PbI₃/spiroMeOTAD bulk heterojunction. The integrated planar and bulk dual heterojunction based PSCs are efficient in light harvesting and charge collection, and thus yield power conversion efficiencies up to 17.75% and a stabilized power output above 17.20%. Integrating both planar and bulk heterojunctions into a PSC assembly provides an effective approach for fabricating highly efficient perovskite optoelectronic devices.