Integrated planar and bulk dual heterojunctions capable of efficient electron and hole extraction for perovskite solar cells with > 17% efficiency

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.