Despite nearly two decades of research, the absence of ideal flexible and transparent electrodes has been the largest obstacle in realizing flexible and printable electronics for future technologies. ...Here we report the fabrication of 'polymer-metal hybrid electrodes' with high-performance properties, including a bending radius <1 mm, a visible-range transmittance>95% and a sheet resistance <10 Ω sq(-1). These features arise from a surface modification of the plastic substrates using an amine-containing nonconjugated polyelectrolyte, which provides ideal metal-nucleation sites with a surface-density on the atomic scale, in combination with the successive deposition of a facile anti-reflective coating using a conducting polymer. The hybrid electrodes are fully functional as universal electrodes for high-end flexible electronic applications, such as polymer solar cells that exhibit a high power conversion efficiency of 10% and polymer light-emitting diodes that can outperform those based on transparent conducting oxides.
Despite the recent unprecedented increase in the power conversion efficiencies (PCEs) of small‐area devices (≤0.1 cm2), the PCEs deteriorate drastically for PSCs of larger areas because of the ...incomplete film coverage caused by the dewetting of the hydrophilic perovskite precursor solutions on the hydrophobic organic charge‐transport layers (CTLs). Here, an innovative method of fabricating scalable PSCs on all types of organic CTLs is reported. By introducing an amphiphilic conjugated polyelectrolyte as an interfacial compatibilizer, fabricating uniform perovskite films on large‐area substrates (18.4 cm2) and PSCs with the total active area of 6 cm2 (1 cm2 × 6 unit cells) via a single‐turn solution process is successfully demonstrated. All of the unit cells exhibit highly uniform PCEs of 16.1 ± 0.9% (best PCE of 17%), which is the highest value for printable PSCs with a total active area larger than 1 cm2.
Large‐area planar perovskite solar cells (PSCs) are demonstrated by an innovative method using an amphiphilic conjugated polyelectrolyte as an interfacial compatibilizer between the hydrophobic organic charge‐transport layer and hydrophilic perovskite layer. Highly scalable PSCs with uniform perovskite films on a large‐area substrate (18.4 cm2) and with an active area of 1 cm2 exhibit stabilized power conversion efficiencies of 17%.
Stretchable conductive materials have received great attention owing to their potential for realizing next-generation stretchable electronics. However, the simultaneous achievement of excellent ...mechanical stretchability and high electrical conductivity as well as cost-effective fabrication has been a significant challenge. Here, we report a highly stretchable and highly conducting polymer that was obtained by incorporating an ionic liquid. When 1-ethyl-3-methylimidazolium tetracyanoborate (EMIM TCB) was added to an aqueous conducting polymer solution of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), it was found that EMIM TCB acts not only as a secondary dopant but also as a plasticizer for PEDOT:PSS, resulting in a high conductivity of >1000 S cm–1 with stable performance at tensile strains up to 50% and even up to 180% in combination with the prestrained substrate technique. Consequently, by exploiting the additional benefits of high transparency and solution-processability of PEDOT:PSS, we were able to fabricate a highly stretchable, semitransparent, and wholly solution-processed alternating current electroluminescent device with unimpaired performance at 50% strain by using PEDOT:PSS/EMIM TCB composite films as both bottom and top electrodes.
In perovskite solar cells, doped organic semiconductors are often used as chargeextraction interlayers situated between the photoactive layer and the electrodes. The n-conjugated small molecule ...2,2',7,7'-tetrakisA,A-di(4-methoxyphenyl)amino9,9-spirobifluorene (spiro-OMeTAD) is the most frequently used semiconductor in the hole-conducting layer1-6, and its electrical properties considerably affect the charge collection efficiencies of the solar cell7. To enhance the electrical conductivity of spiro-OMeTAD, lithium bis(trifluoromethane)sulfonimide (LiTFSI) is typically used in a doping process, which is conventionally initiated by exposing spiroOMeTAD:LiTFSI blend films to air and light for several hours. This process, in which oxygen acts as the p-type dopant8-11, is time-intensive and largely depends on ambient conditions, and thus hinders the commercialization of perovskite solar cells. Here we report a fast and reproducible doping method that involves bubbling a spiro-OMeTAD:LiTFSI solution with CO2 under ultraviolet light. CO2 obtains electrons from photoexcited spiro-OMeTAD, rapidly promoting its p-type doping and resulting in the precipitation of carbonates. The CO2-treated interlayer exhibits approximately 100 times higher conductivity than a pristine film while realizing stable, high-efficiency perovskite solar cells without any post-treatments. We also show that this method can be used to dope n-conjugated polymers.
Despite the excellent work function adjustability of conjugated polyelectrolytes (CPEs), which induce a vacuum level shift via the formation of permanent dipoles at the CPE/metal electrode interface, ...the exact mechanism of electron injection through the CPE electron transport layer (ETL) remains unclear. In particular, understanding the ionic motion within the CPE ETLs when overcoming the sizable injection barrier is a significant challenge. Because the ionic functionality of CPEs is a key component for such functions, a rigorous analysis using highly controlled ion density (ID) in CPEs is crucial for understanding the underlying mechanism. Here, by introducing a new series of CPEs with various numbers of ionic functionalities, energy level tuning at such an interface can be determined directly by adjusting the ID in the CPEs. More importantly, these series CPEs indicate that two different mechanisms must be invoked according to the CPE thickness. The formation of permanent interfacial dipoles is critical with respect to electron injection through CPE ETL (≤ 10 nm, quantum mechanical tunneling limit), whereas electron injection through thick CPE ETL (20–30 nm) is dominated by the reorientation of the ionic side chains under a given electric field.
An electron injection mechanism for conjugated polyelectrolyte (CPE) electron transport layers in organic electronic devices is demonstrated by introducing a new series of CPEs with various numbers of ionic functionalities. Energy level tuning at the CPE/metal interface can be determined directly by adjusting ion density in the CPEs. Thickness‐dependent electron injection characteristics indicate that two different mechanisms must be invoked according to the CPE thickness.
We investigated the charge dynamics of the conductivity enhancement from 2 to 1000 S/cm in poly(3, 4-ethylenedioxythiophene):poly(styrenesulfonate) as induced by structural changes through the ...addition of a polar solvent and the following solvent bath treatment. Our results indicate that the addition of a polar solvent selectively enhanced the π-π coupling of the polymer chains, resulting in the reduction of disorder and tremendously increasing the charge carrier mobility, which yielded an insulator-to-metal transition. In contrast, the following solvent bath treatment selectively enhanced the intergrain coupling, which did not affect the disorder or the mobility but increased the charge carrier density. Therefore, we demonstrate that the conduction-character defining disorder in this conducting polymer system is determined by the extent of interchain coupling.
Efficient large-area planar heterojunction (PHJ) perovskite solar cells (PSCs) were successfully developed by adapting a scalable doctor blade printing method under ambient condition. To achieve ...high-quality perovskite films onto poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) layer, the PEDOT:PSS was modified by adding poly(4-styrenesulfonic acid) (PSSH), which uses the electrostatic interaction between the sulfonyl functional groups in PEDOT:PSS and perovskite precursor ions. The resulting perovskite film on the modified PEDOT:PSS (M-PEDOT:PSS) exhibited excellent uniformity and surface coverage with high crystallinity even for large-area (15mm×40mm) scale. In addition, the power conversion efficiency (PCE) of the printed PSCs was significantly improved from 6% to 10.15% by introducing our M-PEDOT:PSS layer. This finding provides an important guideline to achieve highly efficient PSCs using scalable printing techniques.
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•Efficient perovskite solar cells were fabricated using a doctor blade method.•The coverage of bladed perovskite films were improved by modifying PEDOT:PSS.•The printable PHJ perovskite solar cells exhibited a high efficiency of 10.15%.•Large-area scale (15mm×40mm) PHJ perovskite solar cell was demonstrated.
The fabrication of organic photovoltaic modules via printing techniques has been the greatest challenge for their commercial manufacture. Current module architecture, which is based on a monolithic ...geometry consisting of serially interconnecting stripe-patterned subcells with finite widths, requires highly sophisticated patterning processes that significantly increase the complexity of printing production lines and cause serious reductions in module efficiency due to so-called aperture loss in series connection regions. Herein we demonstrate an innovative module structure that can simultaneously reduce both patterning processes and aperture loss. By using a charge recombination feature that occurs at contacts between electron- and hole-transport layers, we devise a series connection method that facilitates module fabrication without patterning the charge transport layers. With the successive deposition of component layers using slot-die and doctor-blade printing techniques, we achieve a high module efficiency reaching 7.5% with area of 4.15 cm(2).
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.
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