NIR-Selective electrochromic heteromaterial frameworks: a platform to understand mesoscale transport phenomena in solid-state electrochemical devices

Abstract

We report here the first solid-state, NIR-selective electrochromic devices. Critical to device performance is the arrangement of nanocrystal-derived electrodes into heteromaterial frameworks, where hierarchically porous ITO nanocrystal active layers are infiltrated by an ion-conducting polymer electrolyte with mesoscale periodicity. Enhanced coloration efficiency and transport are realized over unarchitectured electrodes in devices, paving the way towards new smart windows technologies.

Colloidal Nanocrystal Frameworks

“…Poly( N,N -dimethylacrylamide) (PDMA) and copolymers thereof have emerged as superior nanocrystal tethering domains for directing CNF assembly from cationic naked nanocrystals ( Figure 3 ). [ 24,27,29,60 ] In future schemes, related polymer families such as poly(2-oxazolines) [ 71 ] or polypeptoids [ 72 ] might likewise produce similar results.…”

“…[ 62 ] Lastly, in that CNF mesopores can be infi ltrated with an almost endless variety of functional organic, inorganic, or polymeric constituents, an unprecedented heteromaterial synergy -unique to CNFs -can be wielded in a combinatorial manner to discover and develop new concepts for directing energy propagation, amplifi cation, and dissipation via component-controlled mesoscale phenomena. [ 60,61 ] Figure 1. Colloidal nanocrystal frameworks are a new class of mesostructured porous material that can be accessed through the controlled assembly of nanoscale inorganic building units using custom-purposed block copolymer architecture-directing agents.…”

“…[73][74][75][76][77] Kinetic control has been most often used to assemble CNFs from ligand-stripped nanocrystal building units, and in particular from cationic naked nanocrystals, likely due to the strongly attractive nature of nanocrystal-ADA interactions through Lewis acid-Lewis base pairing. [23][24][25][26][27][28][29][30]60,61 ] In this case, nanocrystals can be preassembled with block copolymer micelles to decorate their coronas, creating hybrid supramolecular aggregates that are then packed together during CNF assembly. Ordered composites are reached using standard coating procedures (i.e., dipcoating, spin-coating, blade-coating), requiring only solvent shown.…”

“…Examples of pore-forming microdomains include polystyrene (PS), polyisoprene (PI), poly(propylene oxide) (PPO), poly(butylene oxide) (PBO), and poly(ethylene-altpropylene) (PEP). [21][22][23][24][25][26][27][28][29][30]60,61 ] In rationalizing the successes and failures of different assembly strategies, it's useful to note that, owing to the nanoscale dimensions of the various components, the interface density is exceptionally high. As a result, the enthalpic gains made possible using electrostatics are signifi cant, and ultimately overcome any entropic penalties of mixing.…”

“…[ 27 ] Furthermore, metal oxide CNFs show excellent cycling ability and rate performance in electrochemical devices, even when the charging mechanism is based on intercalation, suggesting nanocrystalnanocrystal junctions holding the framework together are fairly robust even when strained at phase or grain boundaries. [ 24,60 ] CNFs therefore represent a versatile material platform to investigate the fundamental transport functions of a broad spectrum of energy-converting devices, including capacitors, batteries, photovoltaics, solar-to-fuel schemes, electrochromics, and ion-transporting membranes. Because specifi c CNF architectures can now be directly linked to a set of performance characteristics, it should be possible to both parameterize system functions and codify the fundamental design rules underpinning the directional fl ow of energy, electrons, and ions through CNF active layers.…”