Ag-LSPR and molecular additive: A collaborative approach to improve the photovoltaic performance of perovskite solar cells

The development of multi-functional synergetic strategy with defect passivation and optical management is expected to further improve the photovoltaic performance of perovskite solar cells (PSCs). Herein, the small organic molecule of 4-trifluoromethyl pyridine (TFP) and Ag nanoparticle modified by TFP (Ag@TFP) with local surface plasmon resonance (LSPR) effects were introduced into PSCs. After investigating their different intervention ways in PSCs, a novel technique has been proved to own the ability to achieve the best photovoltaic performance of PSCs, i.e. TFP was introduced into the perovskite layer by anti-solvent method, and then a layer of Ag@TFP was deposited on the perovskite layer. The TFP can both coordinate with Pb related defects and form hydrogen bonds with MA+ and FA+ to effectively inhibit ion migration, so that the perovskite films with high crystal quality and improved stability can be obtained. The further deposition of Ag@TFP enhances the light absorption of perovskite via far-field light scattering effects and produces hot electrons for injection, so that the Jsc and Voc can be greatly increased. Meanwhile, an enhanced near-field electromagnetic field of Ag@TFP increases the build-in field of device, and a more matched energy level alignment has been formed, which greatly accelerates the charge transfer from perovskite to HTL. As a result, the highest PCE of 23.86 % has been achieved in the Ag@TFP-TFP based Cs0.069FA0.826MA0.105Pb(I0.955Br0.045)3 PSCs. This work not only provides an effective approach to improve the photovoltaic performance of PSCs, but also open a new gate to design synergetic strategy with multifunction for prompting the development of PSCs.