An Improbable Amino-Functionalized Fullerene Spacer Enables 2D/3D Hybrid Perovskite with Enhanced Electron Transport in Solar Cells

2D perovskites possess superior humidity stability but inferior power conversion efficiency (PCE) compared with 3D perovskites due to their typically insulating spacers. Size of the spacer cation is determinative for the formation of 2D perovskite, and fullerene is believed not to be capable of templating 2D perovskite structure because of its larger size than the width of the lead-halide octahedron despite its well-known strong electron-accepting ability. Herein, a novel amino-functionalized fullerene derivative (abbreviated as C-60-BPAM) is developed and an 'improbable' spacer for 2D/3D hybrid perovskite solar cells (PSCs), achieving enhanced electron transport is applied. Unlike most of the reported alkylammonium spacers that are based on insulating organic tails, the incorporation of a highly conductive fullerene tail within C-60-BPAM(2+) leads to increased electron density in 2D/3D perovskite and induces an additional built-in electric field, facilitating electron transport in PSCs. Besides, the 2D/3D hybrid structure helps to passivate both of the shallow- and deep-level defects within perovskite. As a result, the PCE of 2D/3D PSCs improves from 19.36% (3D MAPbI(3) PSCs) to 20.21%. Moreover, the 2D/3D PSCs show significant improvement in the humidity stability compared to the 3D counterparts.

Automated summary

2D/3D hybrid perovskite solar cells with a novel amino-functionalized fullerene derivative as a spacer achieved enhanced electron transport and improved humidity stability. The introduction of a fullerene tail increased electron density and induced an additional built-in electric field, improving electron transport in PSCs.