Electrolyte additive strategy for uniform nucleation of Cu-Bi toward low-voltage self-powered dynamic windows

Abstract

Reversible metal electrodeposition devices (RMEDs) powered by solar cells have shown promising prospects in energy-saving buildings, whereas the high driving-voltage and unclear nucleation/growth mechanism of metal particles have hindered their application. Herein, we propose an electrolyte additive strategy to lower driving-voltage and develop an integrated RMED, in which Cu-Bi RMED was driven by CsPbI2Br solar cells. Results confirm that our integrated device can realize a fast chromatic transition from transparent to black only under sunlight, which possesses 62.42% optical contrast and outstanding performance durability. Studies on dynamic nucleation mechanism reveal that the introduction of choline chloride (ChCl) in water can offer more theoretical nucleation sites (from 4.94 to 13.55 μm-2) and facilitate an easier electrodeposition process toward uniform/dense bimetallic films. Experimental results elucidate that the ionic conductivity increases from 0.05 to 0.31 S m-1 and the charge transfer resistance reduces from 3834 to 647 Ω upon introduction of ChCl, leading to a fast nucleation and color-changing at low-driving voltage. Furthermore, CsPbI2Br solar cells with high up to 1.32 V open-circuit voltage guarantee smooth operations of integrated device via Pb(Ac)2 modification and L-phenylalanine (L-PAA) passivation. Hence, the application limitation of RMED might be overcome by introducing appropriate electrolyte strategies.