Optically transparent semiconducting polymer nanonetwork for flexible and transparent electronics

Abstract

Simultaneously achieving high optical transparency and excellent charge mobility in semiconducting polymers has presented a challenge for the application of these materials in future "flexible" and "transparent" electronics (FTEs). Here, by blending only a small amount (∼15 wt %) of a diketopyrrolopyrrole-based semiconducting polymer (DPP2T) into an inert polystyrene (PS) matrix, we introduce a polymer blend system that demonstrates both high field-effect transistor (FET) mobility and excellent optical transparency that approaches 100%. We discover that in a PS matrix, DPP2T forms a web-like, continuously connected nanonetwork that spreads throughout the thin film and provides highly efficient 2D charge pathways through extended intrachain conjugation. The remarkable physical properties achieved using our approach enable us to develop prototype high-performance FTE devices, including colorless all-polymer FET arrays and fully transparent FET-integrated polymer light-emitting diodes.semiconducting polymer | organic electronics | flexible and transparent device | polymer blend | charge transport O ptically transparent and mechanically flexible circuitries have long been desired for next-generation electronics requiring unprecedented features, such as "see-through" visibility, deformability, and even skin-attachable functionality for health care systems (1-3). This new paradigm for electronic applications has motivated researchers to eagerly pursue new innovative semiconducting materials, and one promising candidate is the class of materials called semiconducting conjugated polymers (4). Their unique benefits, including mechanical flexibility, light weight, and processing advantages based on high-throughput fabrication processes using solution-printing technologies, have accelerated the development of these materials as key building blocks for next-generation ubiquitous systems (2, 5, 6). Nevertheless, these materials still cannot fulfill the ultimate requirements for future "flexible" and "transparent" electronics (FTEs). Together with their inferior charge-carrier mobility because of conformational and energetic disorder (7), their high light absorption in the visible range, which is inherent to this class of materials (absorption coefficient ∼10 5 cm −1 ) (8), makes it difficult to apply these materials in FTEs. Indeed, despite extensive investigations seeking a suitable model system for FTEs by varying the polymer-structure design and the processing techniques used, the simultaneous achievement of optical transparency and high mobility in semiconducting polymers remains a formidable challenge (9, 10).Among the various types of semiconducting polymers, lowbandgap polymers using the donor-acceptor (D-A) copolymerization scheme are promising candidate materials for FTE applications. These semiconducting copolymers usually exhibit much less absorption in the visible range compared with other typical midbandgap polymers because of their red-shifted π-π* absorption spectrum, which exhibits strong absorption in the ne...

Reconfigurable Multifunctional Ambipolar Polymer Transistors with Improved Switching-off Capability Upon Non-Uniformly Distributed Compensation Potential

“…AFM height images ( Fig. 2h) exhibit that the surfaces of both pure and blend film were smooth, while the phase images illustrate that the fiber like morphology which attribute to the aggregation of conjugated-polymer chains was formed in the blend film, similar to the reported results of conjugated-polymer and insulator blends 42,43,49 . Thus, according to UV-vis spectroscopy, GIWAXS and AFM results, the PDPP-…”

“…By comparison, we find that the 0-0 peak shows a higher intensity value and the peak position shifts to a larger wavelength after blending with PS. This phenomenon has been observed in several conjugatedpolymer and insulator blends, which demonstrates increased aggregation and ordering of conjugated-polymers in the insulator-matrix 42,43,[49][50][51][52][53][54] . The dashed lines in Fig.…”

“…A small quantity of conjugated-polymers dispersed in the insulator-matrix could effectively improve the device performance (e.g. mobility and stability) [42][43][44][45][46] , and more importantly, the insulator-matrix could help store charges and enhance the stability of stored charges for long time retention. The stored charges in the insulator-matrix could change the local potential of the channel, which is equivalent to the compensation potential applied to the channel.…”

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“…Failing to fully manipulate the distribution of multiple components in a composite-based channel, for instance, may lead to limited reproducibility and large-area uniformity. In addition to the control over the blend solution and annealing, area-selective deposition through anchoring groups and/or the addition of functionally inactive scaffolds can help improve the controllability over phase separation or guide the formation of new nanostructures [ 73 , 82 ].…”

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