Large‐Area Electrochromic Devices on Flexible Polymer Substrates with High Optical Contrast and Enhanced Cycling Stability

Abstract

Large‐area electrochromic devices (ECDs) based on a cathodically‐coloring, side chain‐modified poly(3,4‐ethylene dioxythiophene) (PEDOT) derivative and anodically‐coloring Prussian blue (PB) are assembled by a customized sheet‐to‐sheet (S2S) lamination process. The ECDs with two complementary switching “half‐cells”, based on flexible PET‐ITO substrates, offer enhanced optical properties in terms of visible light transmission change (4–53%), contrast ratio (CR = 93.4) and color neutrality (L* = 77.9, a* = −5.9, b* = −0.6) in the bleached state. The cycling stability is monitored for up to 10 000 switching cycles (97% charge retention). The reported optical, electrochemical, and in operando (in situ) spectroelectrochemical data are obtained from small laboratory‐scale ECDs (active area: 5 × 5 cm2). These results, the homogeneity of the large‐area devices and the scalability of the S2S lamination process are confirmed by measurements on the large ECDs with an active area of 45 × 65 cm2. This large‐area electrochromic film technology with high optical contrast and enhanced cycling stability offers an excellent perspective for further development and scale‐up towards pilot production and the commercialization of flexible ECDs upon their unique materials and processing characteristics.

Scalable Inkjet Printing of Electrochromic Smart Windows for Building Energy Modulation

“…Although some have demonstrated larger area, these EC devices do not offer a highly transparent clear state, and the optical performance is only evaluated at a smaller scale. [17,18] The other works demonstrated relatively fast switching in EC devices at similar scales (%900 cm 2 ), [13,15,16] yet the construction of those devices requires incorporation of metal mesh or a counter electrode, which in a way will also add onto the cost and device complexity.…”

“…[3,14] Up to now, only a few reports demonstrated EC devices with area close to 900 cm 2 , yet the optical performance of these large area EC windows was not evaluated in details. [13,[15][16][17][18] The quantitative field study of energy savings brought by EC smart windows is also lacking. DOI: 10.1002/aesr.202100172 Electrochromic smart windows are promising for green buildings due to energy efficiency, long optical memory effect, and tunable optical transmission.…”

“…[ 3,14 ] Up to now, only a few reports demonstrated EC devices with area close to 900 cm 2 , yet the optical performance of these large area EC windows was not evaluated in details. [ 13,15–18 ] The quantitative field study of energy savings brought by EC smart windows is also lacking.…”

All Solid‐State Flexible Electrochromic‐Organic Light‐Emitting Diode Devices on Single‐Plastic Substrate for See‐Through Display Technologies

“…The resulting EC cell exhibited an optical contrast of 35% and a response time of 25 s. [ 24 ] Recently, Macher et al., demonstrated the effective realization of a large area flexible EC device (45 × 65 cm 2 ) based on two complementary organic EC materials with an UV‐curable polymer electrolyte and assembled by sheet to sheet (S2S) and R2R lamination process. [ 25 ] On the contrary, we reported a simplified device entirely manufactured at room temperature conditions and continuously on a single substrate without, however, any extra UV curing or annealing treatment of the polymer electrolyte. [ 28,5 ] In this case, in a similar way to the all‐inorganic devices, the top electrode acts as a sealant through the direct deposition of a highly transparent indium tin oxide (ITO) electrode atop of the EC film.…”

“…Differently, the adoption of solid-state, non-sticky and dry electrolyte films of inorganic ceramics and SPEs, allows for the manufacturing of monolithic devices in one direction (from the bottom and up), and on a single glass or plastic substrate, by in line processes, such as for example roll-to-roll (R2R) or physical vacuum depositions. [11,12,[22][23][24][25][26][27][28] Since it does not require any additional lamination step of the two EC electrodes, this approach can considerably simplify the fabrication process with a reduction of production costs, speed of manufacturing, and waste of raw materials, representing thus a very promising strategy for industrial exploitation. Among the devices based on inorganic electrolytes, those based on lithium phosphorus oxynitride (LIPON) showed the best EC responses with an optical modulation of about 40% and switching coloring times of 30 s. [22,23] However, the main drawbacks of these electrolytes lie in defects of brittleness, hardness, and low interface compatibility between the electrolyte and the electrode with an increased charge transfer resistance at the interface, limiting their use for flexible smart windows' applications.…”