Electrochimica Acta, Vol.296, 283-293, 2019
LiTFSI/TBP-free hole transport materials with nonlinear pi-conjugation for efficient inverted perovskite solar cells
We have synthesized two non-linear molecules with Y-shaped (XSIn847) and X-shaped (XSIn1453) structures via a facile synthetic route. Comparable to an X-shaped structure, the Y-shaped structural backbone of XSIn847 enables a tight molecular stacking arrangement through multiple intermolecular short contacts, which affords a nest-layer in molecules. As a result, the pristine, Y-shaped XSIn847 gives higher hole-mobility and more effective photoluminescence quenching than does XSIn1453. Additionally, a decreased charge recombination occurs in the XSIn847-fabricated inverted perovskite solar cells. As a consequence, the device based on XSIn847 affords a higher power conversion efficiency of 15.02% than does that of XSIn1453 (12.65%) under standard global AM 1.5 illumination. The efficiency is further improved to 17.16% when using XSIn847 doping with 2, 3, 5, 6-tetrafluoro- 7, 7, 8, 8-tetracyanoquinodimethane, which is much higher than that of the widely-used PEDOT:PSS (11.95%) when measured under the same condition. These results demonstrate that the molecular engineering of hole transport materials with non-linear structure is a promising strategy for designing efficient molecules for inverted perovskite solar cells. (C) 2018 Elsevier Ltd. All rights reserved.