Polythiophene Polymer Research Articles

Long-Range Supramolecular Assembly of a Pyrene-Derivatized Polythiophene/MWCNT Hybrid for Resilient Flexible Electrochromic Displays.

Organic electrochromic polymers hold great potential for integration into low-power flexible electrochromic displays (F-ECDs) due to their wide range of colors and simple processing. However, challenges such as inefficient charge transfer and degradation upon device integration hinder their practical applications. Herein, we report an innovative, general approach that utilizes template-induced supramolecular nanostructuring to engineer established electrochromic polymers, enhancing their performance and durability. We modified a well-known, albeit underperforming in F-ECDs, poly-thiophene polymer (ECP Orange; PT) by incorporating a pyrene appendage, resulting in a copolymer (PTPy) capable of undergoing large-scale assembly in the presence of multi-walled carbon nanotubes (MWCNTs), driven by the establishment of π-π interactions between the pyrene and the MWCNTs (PTPy/MWCNTs). F-ECDs based on these hybrids, produced by spray coating, exhibit improved color switching speeds (t 90 OX = 3.6 s, t 90 RED = 0.3 s) compared to those of the PT polymer (t 90 OX = 53.2 s, t 90 RED = 2.5 s). Additionally, PTPy/MWCNTs F-ECDs demonstrate longer cyclability (half-life based on ΔE, ΔE 50% = 17.6k cycles) compared to PT (ΔE 50% = 278 cycles), also when blended with MWCNTs (ΔE 50% = 282 cycles). This work highlights the pivotal role of engineered supramolecular nanostructuring in boosting the performance of organic electrochromic materials, making them suitable for F-ECD scalable commercial applications.

Morphological and molecular control of chemical vapor deposition (CVD) polymerized polythiophene thin films.

Oxidative chemical vapor deposition (oCVD) has emerged as one of the most promising techniques for conjugated polymer deposition, especially for unsubstituted polythiophene thin films. oCVD overcomes the insolubility challenge that unsubstituted polythiophene (PT) presents and adds the ability to control morphological and molecular structure. This control is important for enhancing the performance of devices which incorporate organic conductors. In this work, Raman spectroscopy, UV-vis spectroscopy, and AFM reveal that the relative amount of distortion in the polymer chains, the conjugation length and the film roughness are all affected by the CVD deposition conditions, in particular the reactor pressure. PT films deposited at 150 mT and 300 mT are found to have lower chain distortion, longer conjugation lengths and lower surface roughness compared to other deposition pressures. The oCVD PT film is also directly grafted to the trichloro(phenylethyl)silane (PTS) treated substrates, where the effect of PTS grafting is observed to significantly affect film roughness. In addition, we report the first study of the effect of oCVD PT films on the performance of lithium-ion battery electrodes. These oCVD PT films are used to engineer a LiCoO2 cathode in lithium-ion batteries. The observed improvements are a 52% increase in the discharge capacity (67 mA h g-1 to 102 mA h g-1) at 10C and a 500% improvement in cycling stability tested at 5C within the voltage range of 3.0-4.5 V (capacity fading rate is reduced from 1.92%/cycle to 0.32%/cycle).

Doped activated carbons obtained from nitrogen and sulfur-containing polymers as metal-free catalysts for application in nitroarenes hydrogenation

Activated carbons doped with nitrogen and/or sulfur have been obtained by pyrolysis followed of steam activation of a sulfur containing polymer (polythiophene) and two nitrogen-containing polymers (polyaniline and polypyrrole). These polymers were synthesized by oxidative chemical polymerization in aqueous media of their corresponding monomers.The influence of the steam activation on the textural properties and surface chemistry of the carbons has been evaluated and their catalytic activity has been determined in the hydrogenation reaction of 1-chloro-4-nitrobenzene. The degree of conversion in the reaction depends on the development of adequate porosity in the activated carbon (which is determined by the activation conditions) together with the presence of heteroatoms that act as active catalytic sites, with S showing considerably greater effectiveness than N. A compromise between an acceptable level of doping with sulfur and an adequate porosity is necessary, which has been achieved in a carbon obtained from polythiophene pyrolyzed at 900 °C and steam activated at 800 °C for 4 h, with a specific surface area of 742 m2/g and S content of 1.71 at%.

Graphene Nanocomposites for Electromagnetic Interference Shielding—Trends and Advancements

Electromagnetic interference is considered a serious threat to electrical devices, the environment, and human beings. In this regard, various shielding materials have been developed and investigated. Graphene is a two-dimensional, one-atom-thick nanocarbon nanomaterial. It possesses several remarkable structural and physical features, including transparency, electron conductivity, heat stability, mechanical properties, etc. Consequently, it has been used as an effective reinforcement to enhance electrical conductivity, dielectric properties, permittivity, and electromagnetic interference shielding characteristics. This is an overview of the utilization and efficacy of state-of-the-art graphene-derived nanocomposites for radiation shielding. The polymeric matrices discussed here include conducting polymers, thermoplastic polymers, as well as thermosets, for which the physical and electromagnetic interference shielding characteristics depend upon polymer/graphene interactions and interface formation. Improved graphene dispersion has been observed due to electrostatic, van der Waals, π-π stacking, or covalent interactions in the matrix nanofiller. Accordingly, low percolation thresholds and excellent electrical conductivity have been achieved with nanocomposites, offering enhanced shielding performance. Graphene has been filled in matrices like polyaniline, polythiophene, poly(methyl methacrylate), polyethylene, epoxy, and other polymers for the formation of radiation shielding nanocomposites. This process has been shown to improve the electromagnetic radiation shielding effectiveness. The future of graphene-based nanocomposites in this field relies on the design and facile processing of novel nanocomposites, as well as overcoming the remaining challenges in this field.

Regioisomeric Cyanated Polythiophenes Bearing Polar Side Chains for n-Type Organic Thermoelectrics

The development of n-type polymers with high thermoelectric performance remains a major challenge for organic thermoelectrics. Herein, by devising two new isomeric cyano-functionalized bithiophene building blocks bearing polar side chains, we report two novel donor–acceptor-configurated n-type polythiophene polymers (BTOgCN-FT and BTCNOg-FT) with regiochemically tuned intramolecular S···O noncovalent interactions (INIs) and cyanation patterns for n-type thermoelectric application. The results show that cyanation furnished low-lying LUMO energy levels approaching that of the benchmark n-type polymer N2200 for both polymers (∼−3.90 eV), which combine with their polar side chain-enabled high dopant miscibility, leading to efficient n-doping efficiencies. Detailed theoretical and experimental studies also suggest that BTOgCN-FT exhibited a more planar backbone conformation and more ordered interchain packing in film state, thus yielding higher electrical values than BTCNOg-FT. Therefore, the polymer BTOgCN-FT eventually displays an optimal power factor (PF) value of 2.77 μW m–1 K–2, which is higher than that of BTCNOg-FT (1.50 μW m–1 K–2) and also largely outperforming that of the thoroughly investigated and optimized polymer N2200 (typical PF value of 10–2 μW m–1 K–2). Our work not only presents two novel structurally simple and isomeric electron-accepting building blocks but also offers valuable structure–property correlations for the future design of high-performance n-type thermoelectric materials.

Effect of heteroatoms on structural, electronic and spectroscopic properties of polyfuran, polythiophene and polypyrrole: A hybrid DFT approach

In the present manuscript a brief discussion about the new generation of plastic or polymer also called materials of 21st century was conducted. A comparative study of the structural, electronic and spectroscopic properties of the three heterocyclic polymers polypyrrole, polythiophene and polyfuran in neutral form of particular interest has been carried out using the result of Density Function Theory B3LYP/6-31G (d, p) methods. Also how theoretical methods utilizing quantum chemical calculations can be employed to study various properties of these new generation polymers and what information's can be drawn from them about their structural and electronic properties has been discussed. Our major concern is to study the effect of heteroatom i-e O, N, S on electronic, structural and spectroscopic properties of Furans, Pyrrole and Thiophenes. For this purpose, the important structural properties (geometric parameters, charge analysis) spectroscopic properties (vibrational and VU–vis spectra's) and electronic properties (HOMO, LUMO and band gap) of these polymers are compared. The calculated trend in the values of different properties (electronic, structural and spectroscopic) of the polymers is an excellence agreement with available experimental values. The theoretical calculation predicted the order of more attraction as polythiophene (PTh) ˃ polyfuran (PF) ˃ polypyrrole (PPy) from optimized geometric parameters, the Spectroscopic study predict that the λmax absorption shown in the order of PTh ˃ PF ˃ PPy, the HOMO, LUMO and band gap calculation also go side by side with the result obtained from structural and spectroscopic properties calculation

Water-Soluble Conductive Composite Binder for High-Performance Silicon Anode in Lithium-Ion Batteries

The design of novel and high-performance binder systems is an efficient strategy to resolve the issues caused by huge volume changes of high-capacity anodes. Herein, we develop a novel water-soluble bifunctional binder composed of a conductive polythiophene polymer (PED) and high-adhesive polyacrylic acid (PAA) with abundant polar groups. Compared with conventional conductive additives, the flexible conductive polymer can solve the insufficient electrical contact between active materials and the conductive agent, thus providing the integral conductive network, which is extremely important for stable electrochemical performance. Additionally, the polar groups of this composite binder can form double H-bond interactions with the hydroxyl groups of SiO2 layers onto the silicon surface, keeping an integral electrode structure, which can decrease the continuous formation of SEI films during the repeated cycles. Benefiting from these bifunctional advantages, the Si electrodes with the composite binder delivered a high reversible capacity of 2341 mAh g−1 at 1260 mA g−1, good cycle stability with 88.8% retention of the initial reversible capacity over 100 cycles, and high-rate capacity (1150 mAh g−1 at 4200 mA g−1). This work opens up a new venture to develop multifunctional binders to enable the stable operation of high-capacity anodes for high-energy batteries.

An Electroactive Filter with Tunable Porosity Based on Glycolated Polythiophene

The porosity of filters is typically fixed; thus, complex purification processes require application of multiple specialized filters. In contrast, smart filters with controllable and tunable properties enable dynamic separation in a single setup. Herein, an electroactive filter with controllable pore size is demonstrated. The electroactive filter is based on a metal mesh coated with a polythiophene polymer with ethylene glycol sidechains (p(g3T2)) that exhibit unprecedented voltage‐driven volume changes. By optimizing the polymer coating on the mesh, controllable porosity during electrochemical addressing is achieved. The pores reversibly open and close, with a dynamic range of more than 95%, corresponding to over 30 μm change of pores’ widths. Furthermore, the pores’ widths could be defined by applied potential with a 10 μm resolution. From among hundreds of pores from different samples, about 90% of the pores could be closed completely, while only less than 1% are inactive. Finally, the electroactive filter is used to control the flow of a dye, highlighting the potential for flow control and smart filtration applications.

Recent developments in sensing of oversulfated chondroitin sulfate in heparin. A review.

Oversulfated chondroitin sulfate (OSCS), a non-natural sulfated glycosaminoglycan, recognizes as a significant containment in the pharmaceutical heparin, and it could trigger adverse reactions. Chromatography-, electrophoresis-, electrochemistry-, and spectroscopy-related techniques are currently available for accurate and precise analysis of a trace amount of OSCS in heparin. Recently, emerging studies focus on developing colorimetric and fluorescent probes to monitor OSCS containments in heparin. Therefore, this current review aims to describe the sensing principle and procedure of the reported probes that are sensitive and selective toward OSCS in heparin without the interferences of other sulfated glycosaminoglycans. The reported OSCS-specific probes are comprehensively discussed according to the recognition elements of OSCS, including coralyne, AG73 peptides, positively charged tetraphenylethene derivatives, polythiophene polymer, and poly-L-lysine, protamine, superpositively charged green fluorescent proteins, and poly (diallyldimethylammonium chloride). The sensing of OSCS in heparin is generally achieved using, (i) the specific affinity of the recognition element with OSCS and heparin, (ii) heparinase-mediated hydrolysis of heparin, and (iii) OSCS-induced inhibition of heparinase activity. Additionally, coralyne-based DNA probes can detect OSCS in heparin in the presence of Ca2+ ions without the assistance of heparinase. This review will pave the way to design another sensing probe towards other sulfated contaminants, like dermatan sulfate.

Catalysing electropolymerization: High-quality polythiophene films for electrochemical sensors by the utilization of fluorine based Lewis acid catalysts

Polythiophene and other conductive polymers can be obtained by electropolymerization from various solvents, of which boron trifluoride diethyl etherate (BFEE) is preferably used. In this solvent, electropolymerization can be performed at significantly lower potentials and therefore milder conditions, from which polymers with improved properties result. However, their quality cannot easily be reproduced. We discovered the mechanism behind the decreased initial oxidation potential of thiophene in BFEE and transferred it onto stable solvents by the utilization of fluorine based Lewis acid catalysts. By exemplarily utilizing zinc fluoride in acetonitrile, we found that the catalysis allows for lower oxidation potentials, higher selectivity of polymerization, and smoother film surface morphology – in a reproducible manner. The presented polythiophene films constitute a promising substrate material for the fabrication of electrochemical sensors. Films were deposited by cyclic voltammetry, chronoamperometry, and chronopotentiometry, and characterized by electrochemical impedance spectroscopy and Raman spectroscopy. Surface morphology and elemental composition were analysed with white light interferometry, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. We propose a number of alternative catalysts that can be utilized in various solvents, not just for thiophene electropolymerization, but for various other conductive polymers. The presented catalysis can therefore serve as a universal tool for the synthesis of high quality conductive polymer films for innovative and trendsetting applications.

Fast, simple, and gentle method for removal of polythiophene and other conductive polymer films from gold electrodes

Polythiophene is a prominent conductive polymer that can easily be deposited on electrodes in thin films. Polythiophene films convince with protein repellent properties and excellent environmental stability, which makes them an ideal candidate for the construction of various sensors. However, due to the strong absorption of polythiophene onto gold, its removal is a challenging task. Therefore, we developed a new method for the fast, simple and gentle removal of polythiophene films from gold electrodes. It is based on the induction of a shear stress caused by film swelling and allows the films to be easily wiped off the electrodes after treatment. The protocol is versatile and can be applied to a series of solvents, counter ions, and other conductive polymers; it even enables the removal of polypyrrole with a solution as simple as aqueous sodium sulphate. The quality of cleaned electrodes was evaluated using electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and white light interferometry. Our protocol allowed to reuse the utilized screen-printed thick film electrodes for up to fifteen times and hopefully supports the community in their research regarding the interesting and future oriented field of conductive polymers.

Flexible cellulose/polyvinyl alcohol/PEDOT:PSS electrodes for ECG monitoring

Electrocardiography is one of the most significant technologies for detecting cardiovascular diseases. Nowadays, the problems of various electrodes still meet a great challenge. Herein, we design a low cost, environmentally friendly and flexible conductive electrode using cellulose and polyvinyl alcohol as a substrate assembled with conductive polymer polythiophene by in situ oxidative polymerization, and the green solvent 1-butyl-3-methylimidazolium chloride as a crosslinking agent. The polyvinyl alcohol/cellulose/PEDOT:PSS(PCPP) composite electrode has excellent features of flexibility, low skin contact impedance and comfortable contact with skin. When the load of EDOT reaches 15 wt%, the electrode is stable and can clearly monitor the characteristic wave of ECG signals. Therefore, based on cellulosic biopolymer and conductive polymer PEDOT:PSS, an environmentally friendly, flexible and stable PCPP composite electrode is obtained and can be a promising candidate applied in the fields of energy storage and ECG sensing.

3D Printable Electrically Conductive Hydrogel Scaffolds for Biomedical Applications: A Review.

Electrically conductive hydrogels (ECHs), an emerging class of biomaterials, have garnered tremendous attention due to their potential for a wide variety of biomedical applications, from tissue-engineered scaffolds to smart bioelectronics. Along with the development of new hydrogel systems, 3D printing of such ECHs is one of the most advanced approaches towards rapid fabrication of future biomedical implants and devices with versatile designs and tuneable functionalities. In this review, an overview of the state-of-the-art 3D printed ECHs comprising conductive polymers (polythiophene, polyaniline and polypyrrole) and/or conductive fillers (graphene, MXenes and liquid metals) is provided, with an insight into mechanisms of electrical conductivity and design considerations for tuneable physiochemical properties and biocompatibility. Recent advances in the formulation of 3D printable bioinks and their practical applications are discussed; current challenges and limitations of 3D printing of ECHs are identified; new 3D printing-based hybrid methods for selective deposition and fabrication of controlled nanostructures are highlighted; and finally, future directions are proposed.

Atomically dispersed cobalt-based species anchored on polythiophene as an efficient electrocatalyst for oxygen evolution reaction

For clean and renewable energy conversion systems, it is important to develop efficient, earth-abundant, low-cost and stable electrocatalysts for oxygen evolution reaction (OER). Herein, we prepared an atomically dispersed cobalt coordinated with oxygen and sulfur species on the conductive polymer polythiophene (PTh) via CoS bond as a stable noble-metal-free electrocatalyst for the OER. A novel cobalt-based catalytic site structure, CoxOyS4, is successfully fabricated. The resulting electrocatalyst, Co@PTh, exhibits an excellent OER performance with overpotential of 338 mV versus reversible hydrogen electrode (RHE) at a current density of 10 mA cm−2 and the Tafel slope of 52 mV dec−1 in alkaline electrolyte. This performance is better than that of the commercial RuO2 and even comparable with the state-of-the-art catalyst IrO2. Our work suggests that the atomically dispersed cobalt-based species decorated PTh may be a good alternative for precious-metal-based catalysts.

Random copolymerization of polythiophene for simultaneous enhancement of in‐plane and out‐of‐plane charge transport for organic transistors and perovskite solar cells

High-performance conjugated polymers for electronic applications can be developed by modulating an appropriate chemical structure that optimizes their crystal characteristics and charge-transport behavior. Herein, we demonstrated the simultaneous enhancement of the in-plane and out-of-plane charge transport of polythiophenes by random polymerization. We synthesized a polythiophene polymer by varying the ratio of two different dialkyl-substituted bi-thiophene and triethylene glycol-substituted mono-thiophene units; this polymer exhibited weakened orientation preferences of polymer crystallite films, a denser packing, and a more homogeneous surface morphology in comparison with its homopolymer analogue. Furthermore, this optimized random polymer afforded an enhanced in-plane mobility of 7.72 cm2 V−1 second−1, measured by field-effect transistor, and out-of-plane mobility of 8.86 × 10−4 cm2 V−1 second−1, measured by space-charge-limited-current device. These are respectively 2.4 times and 10 times higher than the mobilities of the homopolymer (field-effect mobility = 3.25 cm2 V−1 second−1 and space-charge-limited-current mobility = 8.73 × 10−5 cm2 V−1 second−1). The enhanced charge transport in out-of-plane direction was also confirmed by fabricating perovskite solar cells using optimized polythiophene as a hole-transporting material, which exhibited a higher efficiency of nearly 16.2% than the device with homopolymer analogue (12.0%).

Flexible Electrochromic Poly(thiophene-furan) Film via Electrodeposition with High Stability

Flexible electrochromic (EC) materials have an urgent demand in the current electronic equipment market due to their technological interest and applications. However, at present, few flexible EC devices developed by industry exist due to some problems and challenges still to be solved such as flexibility. In this work, we have successfully synthesized a novel thiophene-furan (TFu) monomer via Stille coupling reaction, and facilely electrochemically polymerized in a neutral Bu4NPF6-CH2Cl2 electrolyte system to afford the corresponding poly(thiophene-furan) (PTFu) polymer film with good flexibility. The electrochemical and photoelectrochemical analyses of the as-prepared PTFu demonstrate that it has achieved the improved EC performance compared with pure polyfuran and polythiophene polymers, and as a result it possesses favorable EC parameters manifested as a reasonable ΔT (32.1%), faster response (1.38 s), excellent coloration efficiency (CE, 300.9 cm2·C−1), and after a continuous redox process up to 2000 s, its optical stability can be maintained at 96%, and even after 3000 s, it can still be maintained at 80%. In addition, the successful assembly of the electrochromic device of PTFu film can easily realize the reversible conversion of the color from orange to gray. All these systematic studies suggest that the as-prepared flexible PTFu film is a promising candidate for EC materials and has great potential interest for versatile EC applications.

Construction of succinimide group substituted polythiophene polymer functionalized sensing platform for ultrasensitive detection of KLK 4 cancer biomarker

A novel impedimetric immunosensor based on conjugated succinimide group substituted polythiophene polymer (SucS-PThi) modified indium tin oxide (ITO) electrode was fabricated for ultra-sensitive and ultra-selective determination of kallikrein 4 (KLK 4) antigen in diluted human serum. The basic reason for the usage of SucS-PThi polymer was that its rich effective functional groups and biocompatibility. KLK 4, an important prostate biomarker was the target analyte and anti-KLK 4 antibodies immobilized electrode was the diagnostic tool for KLK 4 antigen detection. The fabricated biosensor was characterized by employing electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX), fourier transform-infrared (FTIR) and Raman spectroscopy. Under optimized conditions, a linear concentration range from 0.04 pg/mL to 30 pg/mL and a low detection limit (LOD) of 12.2 fg/mL were obtained and the LOD was lower than of most of the existing techniques, illustrating its feasibility for practical application. Moreover, the developed sensing system combined the outstanding properties in terms of selectivity, sensitivity, repeatability, reproducibility and reusability, without requiring for labor − intensive labeling stages. In addition, it was successfully utilized for accurate quantification of KLK 4 antigen in human serum samples.

Configurationally Random Polythiophene for Improved Polymer Ordering and Charge-Transporting Ability.

Random polythiophene polymers are characterized by the arbitrary sequences of monomeric units along polymer backbones. These untailored orientations generally result in the twisting of thiophene rings out of the conjugation planarity in addition to steric repulsions experienced among substituted alkyl chains. These tendencies have limited close polymer packing, which has been detrimental to charge transport in these moieties. To ameliorate charge transport in these classes of polymers, we make use of simple Stille coupling polymerization to synthesize highly random polythiophene polymers. We induced a positive microstructural change between polymer chains by attuning the ratio between alkyl-substituted and nonalkyl-substituted monomer units along the backbones. The optimized random polythiophene was found to have enhanced intermolecular interaction, increased size of crystallites, and stronger tendency to take edge orientation compared with both regiorandom and regioregular poly(3-hexylthiophene) polymers. Incorporation of the optimized random polythiophene as an active material in solid-state electrolyte-gated organic field-effect transistors exhibited better performance than the control device using regioregular poly(3-hexylthiophene), with a high hole mobility up to 4.52 cm2 V-1 s-1 in ambient conditions.

Nanocomposites based on graphene analogous materials and conducting polymers: a review

Interest in nanocomposite materials has grown rapidly over the past decade. In this time, graphene, graphene analogs, and polymers have increasingly found use as components in nanocomposite materials. Combining multiple materials at the nanoscale provides an opportunity to produce nanocomposites with unique and in many cases enhanced properties. Conductivity is one such property, which can be enhanced through the interaction of multiple materials at the nanoscale. In this review, we highlight nanocomposites derived from graphene analogous materials (MoS2, WS2, BN, MXenes) and electronically conducting polymers (polyaniline, polypyrrole, polythiophene, and derivatives). Methods of nanocomposite preparations including solution or nanodispersion mixing, melt mixing, and in situ polymerization are discussed, as well as specific applications of nanocomposite materials.

Effects of doping methods and dopant sizes on the performance of solar cells constructed with anchor-guided photoelectrochemical polymerization of thiophene

Solar cells constructed with well-ordered polythiophene (PT) or other π-conjugated polymer films are known to yield better photovoltaic characteristics. We recently constructed a PT-based solar cell (PTSC) wherein the photoactive PT film was grown photoelectrochemically along a dye anchor, 3-{5-[N,N-bis(4-diphenylamino)phenyl]thieno[3,2-b]thiophen-2-yl}-2-cyano-acrylic acid (C207) pre-adsorbed onto a compact TiO2 layer. In an effort to understand the effects of other important factors contributing to the PTSC performance, we compared ex-situ and in-situ doping of ordered PT films with three different alkylammonium cations, tetrabutylammonium (TBA+), tetraethylammonium (TEA+), and tetramethylammonium (TMA+). The PT films that have undergone such ex- and in-situ doping both show higher open-circuit voltage (Voc) and short-circuit current density (Jsc) than their pristine counterparts. The optimal conversion efficiency (η) of 7.53 ± 0.58% was achieved via in-situ PT doping with TMA+. The incident photon-to-electron conversion efficiency (IPCE), electrochemical impedance, and electron lifetime measurements all indicate that in-situ doping is less affected by the cation size and can lead to a higher doping level than the ex-situ doping method. The IPCE also benefits from the use of a thin TiO2 layer, as more light reaches the PT film to generate photohole/electron pairs. With the combined use of a thin layer of TiO2 and an ordered PT film containing a large number of dopant ions, the photohole/electron recombination is significantly suppressed.