Electrochemistry and Electrochemiluminescence of Organometal Halide Perovskite Nanocrystals in Aqueous Medium

Abstract

The redox nature and electrochemiluminescence (ECL) of highly crystallized organometal halide perovskite CHNHPbBr nanocrystals (NCs) in aqueous medium were investigated for the first time. CHNHPbBr NCs could be electrochemically reduced to negative charge states by injecting electrons into the lowest unoccupied molecular orbitals and oxidized to positive charge states by removing electrons from the highest occupied molecular orbitals; charge transfer between NCs with positive and negative charge states could produce ECL. The redox sequence of CHNHPbBr NCs played an important role in the generation of charge-transfer-mediated ECL; transient ECL could be achieved only by electrochemically reducing positive-charged NCs in an annihilation route. A large redox current was unfavorable for ECL. Charge mobility within CHNHPbBr NCs had an important effect on ECL intensity in a co-reactant route, which is promising for photovoltaic and optoelectronic device applications. Importantly, the ECL spectra of CHNHPbBr NCs were almost identical to their photoluminescence spectra, with a maximum emission around 535 nm and full width at half-maximum around 25 nm; this might open a way to obtaining monochromatic ECL using highly crystallized NCs as emitters, which makes them promising for use in color-selective ECL analysis.

Pre‐oxidation of Gold Nanoclusters Results in a 66 % Anodic Electrochemiluminescence Yield and Drives Mechanistic Insights

“…Meanwhile, the onset of luminescence occurred near 0.6 V, and the ECL intensity reached a maximum near 0.97 V, which was consistent with the oxidation potential of the CV response. This low potential required for luminescence was superior than other anodic ECL materials including bovine albumin‐protected AuNCs, perovskite quantum dots, CuInS 2 nanocrystals, graphene quantum dots, and Ru(bpy) 3 2+ and its derivatives (often >1.2 V) since a low potential allows for better stability and application.…”

Photophysics of Methylammonium Lead Tribromide Perovskite: Free Carriers, Excitons, and Sub‐Bandgap States

“…The effect causes the shift of the valence band maxima (VBM) [102] and conduction band minima (CBM) away from the high symmetry points in the Brillouin zone, giving rise to LE indirect tail states. [103,104] As shown in the same figure, the shift for Pb-based perovskites in reciprocal space is expected to be larger for the CBM compared to that of the VBM due to the relative orbital contributions to the band structure, [105] allowing an LE indirect transition alongside the HE direct one. The recombination from the LE and HE to the VB then leads to the dual emission.…”

Perovskite Solar Cells: From the Laboratory to the Assembly Line

“…PSC architecture is quite simple in its standard configuration:aconductive glass (or plastic foil) supports an electron extraction layer (like TiO 2 or SnO 2 [13] ), on top of which the perovskite-active material is deposited.Ahole-transporting material (HTM) is coated above the perovskite layer,a nd gold backcontactsa re evaporated on the top of the cell. [14][15][16][17] Sunlight absorption leads to charge-generation, and both negative and positivec hargec arriers are transported through the perovskite to charges electivec ontacts.T he core of this device is the perovskitel ayer,b earing ag eneric structure ABX 3 ,i nw hich Ai sa monovalentc ation (like methylammonium CH 3 NH 3 + ,f ormamidinium CH 2 (NH 2 ) 2 + ,C s + ,R b + ), Bs tands for Pb II or Sn II and X for Io rB r. [18] The successo ft his materials is given by its outstanding optoelectronic properties,m erging high absorption coefficient and mobility,l ow exciton binding energy and long balanced carrier diffusion length; [19][20][21][22][23] moreover,t he device can also work in the inverted configuration. [24] Several review articles have been published on strategies to improve the performance of laboratory-scale PSCs.…”