Fast,Direct, Low‐Cost Route to Scalable,Conductive, and Multipurpose Poly(3,4‐ethylenedixoythiophene)‐Coated Plastic Electrodes

Poly(3,4‐ethylenedioxythiophene) (PEDOT) films are deposited, using an electroless method, onto flexible plastic poly(ethylene terephthalate) (PET) substrates of approximately 20×6 cm². The sheet resistance of a PEDOT–PET film is approximately 600 Ω per square, and the nanoscale conductivity is 0.103 S cm^?1. A plastic electrochromic PEDOT–Prussian blue device is constructed. The device undergoes a color change of pale blue to deep violet–blue reversibly over 1000 cycles, thus demonstrating its use as a light‐modulating smart window. The PEDOT–PET film is also used in a quantum dot solar cell, and the resulting photoelectrochemical performance and work function indicate that it is also promising for photovoltaic cells. The high homogeneity of the PEDOT deposit on PET, the optimal balance between conductivity and optical transparency, and the demonstration of its use in an electro‐optical device and a solar cell, offer the opportunity to use this electrode material in a variety of low‐cost optoelectronic devices.     

Flexible Polymer–Organic Solar Cells Based on P3HT:PCBM Bulk Heterojunction Active Layer Constructed under Environmental Conditions

In this study, some crucial parameters were determined of flexible polymer–organic solar cells prepared from an active layer blend of poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) mixed in 1:1 mass ratio and deposited from chlorobenzene solution by spin-coating on poly(ethylene terephthalate) (PET)/ITO substrates. Additionally, the positive effect of an electron transport layer (ETL) prepared from zinc oxide nanoparticles (ZnO np) on flexible photovoltaic elements’ performance and stability was investigated. Test devices with above normal architecture and silver back electrodes deposed by magnetron sputtering were constructed under environmental conditions. They were characterized by current-voltage (I–V) measurements, quantum efficiency, impedance spectroscopy, surface morphology, and time–degradation experiments. The control over morphology of active layer thin film was achieved by post-deposition thermal treatment at temperatures of 110–120 °C, which led to optimization of device morphology and electrical parameters. The impedance spectroscopy results of flexible photovoltaic elements were fitted using two R||CPE circuits in series. Polymer–organic solar cells prepared on plastic substrates showed comparable current–voltage characteristics and structural properties but need further device stability improvement according to traditionally constructed cells on glass substrates.     

Synthesis of tetracyanoethylene‐substituted ferrocene and its device properties

Small organic molecules are promising candidates for cheaper, flexible and good‐performance sources for organic solar cells (OSCs) due to their easy fabrication, low cost and slightly cheaper processing. However, the lower power conversion efficiency of OSCs is the main problem for their applications. Ferrocene structures could be the best candidates for the active layers of OSCs due to their unique properties such as thermal and chemical stability. The electrochemical, electro‐optical and solar cell performances of 2,5‐dicyano‐3‐ferrocenyl‐4‐ferrocenylethynylhexa‐2,4‐dienedinitrile (DiCN‐Fc) structures were investigated. First, the electrochemical and electro‐optical properties were examined for finding the highest occupied and lowest unoccupied molecular orbital values and bandgap of DiCN‐Fc. The best photovoltaic performance was obtained with 7 wt% of DiCN‐Fc loading, with a power conversion efficiency of about 4.27%. In the light of our investigations, ferrocenyl‐substituted small organic molecules could contribute to the development of organic photovoltaic devices.     

Effect of Device Fabrication Conditions on Photovoltaic Performance of Polymer Solar Cells Based on Poly(3‐hexylthiophene) and Indene‐C70 Bisadduct

Effect of the device fabrication conditions on photovoltaic performance of the polymer solar cells based on poly(3‐hexylthiophene) (P3HT) as donor and indene‐C₇₀ bisadduct (IC₇₀BA) as acceptor was studied systematically. The device fabrication conditions we studied include pre‐thermal annealing temperature, active layer thickness, and the P3HT:IC₇₀BA weight ratios. For devices with a 188‐nm‐thick active layer of P3HT:IC₇₀BA (1:1, w:w) blend film and pre‐thermal annealing at 150°C for 10 min, maximum power conversion efficiency (PCE) reached 5.82% with V_oc of 0.81 V, I_sc of 11.37 mA/cm², and FF of 64.0% under the illumination of AM1.5G, 100 mW/cm².     

Impact of environmentally friendly processing solvents on the properties of blade‐coated polymer solar cells

High‐performance polymer solar cells (PSCs) are typically fabricated by spin coating in inert atmosphere from toxic halogenated solvents such as 1,2‐dichlorobenzene (o‐DCB) and chlorobenzene. This fabrication process is potentially hazardous for both the humans and the environment and dramatically impacts the possibility for the organic photovoltaic technology to be adopted at large scale. In this work, efficient PSCs blade coated in air using nonhalogenated 1,2,4‐trimethylbenzene (TMB) as processing solvent are demonstrated. The active layer, based on a previously synthesized benchmark polymer PFQ2T‐benzodithiophene blended with [6,6]‐phenyl‐C61‐butyric acid methyl ester (PC₆₁BM), showed an enhanced solid‐state aggregation induced by the use of TMB. Compared to o‐DCB‐processed devices, the solar cells fabricated from TMB resulted 10% more efficient with a power conversion efficiency of 4.20%. Interestingly, the improved photovoltaic performance resulted from the combination of synergic effects promoted by a more favorable film morphology, such as high exciton dissociation efficiency and lower bimolecular recombinations resulting in higher charge collection efficiency at the electrodes. The positive effect of TMB, compared to that of commonly employed halogenated solvents, confirms the great potential of this approach for the development of efficient PSCs for practical applications with reduced environmental impact. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 487–494     

Flexible Near‐Infrared Photovoltaic Devices Based on Plasmonic Hot‐Electron Injection into Silicon Nanowire Arrays

The development of flexible near‐infrared (NIR) photovoltaic (PV) devices containing silicon meets the strong demands for solar utilization, portability, and sustainable manufacture; however, improvements in the NIR light absorption and conversion efficiencies in ultrathin crystalline Si are required. We have developed an approach to improve the quantum efficiency of flexible PV devices in the NIR spectral region by integrating Si nanowire arrays with plasmonic Ag nanoplates. The Ag nanoplates can directly harvest and convert NIR light into plasmonic hot electrons for injection into Si, while the Si nanowire arrays offer light trapping. Taking the wavelength of 800 nm as an example, the external quantum efficiency has been improved by 59 % by the integration Ag nanoplates. This work provides an alternative strategy for the design and fabrication of flexible NIR PVs.     

Layer‐by‐Layer Assembled Conductive Metal–Organic Framework Nanofilms for Room‐Temperature Chemiresistive Sensing

The utility of electronically conductive metal–organic frameworks (EC‐MOFs) in high‐performance devices has been limited to date by a lack of high‐quality thin film. The controllable thin‐film fabrication of an EC‐MOF, Cu₃(HHTP)₂, (HHTP=2,3,6,7,10,11‐hexahydroxytriphenylene), by a spray layer‐by‐layer liquid‐phase epitaxial method is reported. The Cu₃(HHTP)₂ thin film can not only be precisely prepared with thickness increment of about 2 nm per growing cycle, but also shows a smooth surface, good crystallinity, and high orientation. The chemiresistor gas sensor based on this high‐quality thin film is one of the best room‐temperature sensors for NH₃ among all reported sensors based on various materials.     

Synthesis of organic sulfobetaine‐based polymer gel electrolyte for dye‐sensitized solar cell application

We have synthesized eco‐friendly, economic, and equally efficient polysulfobetaine‐based gel electrolyte to the alternative of liquid electrolyte in the fabrication of dye‐sensitized solar cells (DSSCs) for the first time. This nitrogen‐rich and highly conductive polysulfobetaine was synthesized by an easy and facile method without the use of any catalyst and explored for its DSSC application. The synthesized polymer gel electrolyte exhibited good ionic conductivity about 6.8 × 10^?3 Scm^?1 at ambient temperatures. DSSCs were fabricated based on this polysulfobetaine gel electrolyte and studied for their performance based on photovoltaic parameters. The DSSC photovoltaic results were appreciable and are Voc = 0.82 V, Jsc = 11.49 mA/cm², FF = 66%, and PCE = 6.26% at 1 sun intensity. These values are slightly lower than conventional liquid electrolyte‐based DSSC shown as Voc = 0.78 V, Jsc = 12.90 mA/cm², FF = 69%, and PCE = 7.07%, both at 100 mWcm^?2. Conductivity and photovoltaic parameters of the device reveals that as prepared polysulfobetaine‐based polymer gel electrolyte may be useful in the fabrication of DSSC and other electrochemical devices. Copyright © 2017 John Wiley & Sons, Ltd.     

Recent Advances in Flexible Perovskite Solar Cells: Fabrication and Applications

Flexible perovskite solar cells have attracted widespread research effort because of their potential in portable electronics. The efficiency has exceeded 18 % owing to the high‐quality perovskite film achieved by various low‐temperature fabrication methods and matching of the interface and electrode materials. This Review focuses on recent progress in flexible perovskite solar cells concerning low‐temperature fabrication methods to improve the properties of perovskite films, such as full coverage, uniform morphology, and good crystallinity; demonstrated interface layers used in flexible perovskite solar cells, considering key figures‐of‐merit such as high transmittance, high carrier mobility, suitable band gap, and easy fabrication via low‐temperature methods; flexible transparent electrode materials developed to enhance the mechanical stability of the devices; mechanical and long‐term environmental stability; an outlook of flexible perovskite solar cells in portable electronic devices; and perspectives of commercialization for flexible perovskite solar cells based on cost.     

Cross‐linked Polymer‐Blend Gate Dielectrics through Thermal Click Chemistry

New cross‐linking reagents were synthesized and mixed with polystyrene (PS) in solution to form a blend. Thin‐films were spin‐coated from the blend and then cross‐linked by thermal activation at relatively low temperature (100 °C) to form cross‐linked gate dielectrics. This new method is compatible with plastic substrates in flexible electronics. The azide and alkyne cross‐linking reagents are kinetically stable at room temperature, so any premature cross‐linking is avoided during processing. This method also significantly improved the dielectric performances of PS thin films. Solution‐processed top‐gate organic field‐effect transistor devices with indacenodithiophene–benzothiadiazole copolymer as semiconductor layer and the cross‐linked PS blend as dielectric layer showed improved performances with lower gate leakages and higher operation stabilities than devices with neat PS film as dielectric layer.     

Graphene‐Based Inverted Planar Perovskite Solar Cells: Advancements,Fundamental Challenges,and Prospects

Metal halide based perovskite solar cells (PSCs) are considered among the most promising photovoltaic technologies, and already present certified efficiencies that surpass 22 %. The high performance and low fabrication cost make this technology competitive with that of state‐of‐the‐art thin‐film photovoltaics. However, PSCs present some striking disadvantages that hinder their commercialization, including short operational lifetimes, high toxicity, and hysteresis effects, which lower both the performance and long‐term stability of the devices. Herein, work conducted within the last two years is summarized with regard to addressing the challenges of low‐temperature‐processed planar inverted PSCs composed of graphene‐based materials. In addition, critical challenges and the prospects of this field are discussed and some prospects for future research directions are proposed.     

Stable and Low‐Cost Mesoscopic CH3NH3PbI2Br Perovskite Solar Cells by using a Thin Poly(3‐hexylthiophene) Layer as a Hole Transporter

Mesoscopic perovskite solar cells using stable CH₃NH₃PbI₂Br as a light absorber and low‐cost poly(3‐hexylthiophene) (P3HT) as hole‐transporting layer were fabricated, and a power conversion efficiency of 6.64 % was achieved. The partial substitution of iodine with bromine in the perovskite led to remarkably prolonged charge carrier lifetime. Meanwhile, the replacement of conventional thick spiro‐MeOTAD layer with a thin P3HT layer has significantly reduced the fabrication cost. The solar cells retained their photovoltaic performance well when they were exposed to air without any encapsulation, presenting a favorable stability. The combination of CH₃NH₃PbI₂Br and P3HT may render a practical and cost‐effective solid‐state photovoltaic system. The superior stability of CH₃NH₃PbI₂Br is also promising for other photoconversion applications.     

Improved Energy Conversion Efficiency of ZnO/Polythiophene Solar Cell in Ga-Doped ZnO Nanorod Array Photoanode

We reported the fabrication and doping effect of Ga-doped ZnO nanorods/electropolymerized polythio-phene(e-PT) hybrid photovoltaic(h-PV) devices. Ga-Doped ZnO nanorod array photoanode devices were fabricated via hydrothermally growing nanorods on sol-gel spin-coating ZnO seed layer, and then the nanorod array was immersed into a thiophene solution to yield a thin polythiophene film by electrochemically polymerization. Afterwards, a thin layer of Al was deposited on the surface of polythiophene to make an electrode for photovoltaic measurement. The ZnO nanorods with different Ga-doping contents were characterized by means of X-ray diffraction(XRD), scanning electron micrograph(SEM) and X-ray photoelectron spectroscopy(XPS). Photovoltaic J-V characterization was performed on the e-PT/ZnO bilayer and bulk heterojunction(BHJ) devices. Though the unsubstituted polythiophene is not an ideal polymer material for solar cells with high power conversion efficiency, it is a sound model for the study on the effect of dopant in hybrid materials. The results indicate that doping Ga can substantially improve the power conversion efficiency of the ZnO-polythiophene solar cell.     

Manufacture and demonstration of organic photovoltaic‐powered electrochromic displays using roll coating methods and printable electrolytes

Electrochromic devices (ECDs) were prepared on flexible substrates using spray coating and slot‐die coating methods. The electrochromic materials were the conjugated electroactive polymers, poly((2,2‐bis(2‐ethylhexyloxymethyl)‐propylene‐1,3‐dioxy)‐3,4‐thiophene‐2,5‐diyl) as a vibrantly colored active material (ECP‐Magenta) and poly(N‐octadecyl‐(propylene‐1,3‐dioxy)‐3,4‐pyrrole‐2,5‐diyl) as a minimally colored, charge balancing material (MCCP). Two electrolyte systems were compared to allow development of fully printable and laminated devices on flexible substrates. Devices of various sizes, up to 7 × 8 cm², are demonstrated with pixelated devices containing pixel sizes of 4 × 4 mm² or 13 × 13 mm². The transmission contrast exhibited by the devices, when switched between the fully bleached and fully colored state, was 58% at a visible wavelength of 550 nm, and the devices exhibited switching times of <10 s. Additionally, we demonstrate the utilization of printed organic photovoltaic devices (with or without the use of a lithium‐polymer battery) to power the devices between the colored and bleached state, illustrating a self‐powered ECD. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Growth of silicon thin film by LPE on porous silicon bilayers

The fabrication of solar cells based on the transfer of a thin silicon film on a foreign substrate is an attractive way to realise cheap and efficient photovoltaic devices. The aim of this work is to realise a thin mono-crystalline silicon film on a double porous silicon layer in order to detach and transfer it on mullite. The first step is the fabrication of a double porous silicon layer by electrochemical anodisation using two different current densities. The low current leads to a low porosity layer and during annealing, the recrystallisation of this layer allows epitaxial growth. The second current leads to a high porosity which permits the transfer on to a low cost substrate. Liquid Phase Epitaxy (LPE) performed with indium (or In+Ga) in the temperature range of 950–1050°C leads to almost homogeneous layers. Growth rate is about 0.35 μm min⁻¹. Crystallinity of the grown epilayer is similar on porous silicon and on single crystal silicon. In this paper, we focus on the realisation of porous silicon sacrificial layer and subsequent LPE growth. This revised version was published online in July 2006 with corrections to the Cover Date.     

Lead‐Free Solar Cells based on Tin Halide Perovskite Films with High Coverage and Improved Aggregation

Two simple methods to improve tin halide perovskite film structure are introduced, aimed at increasing the power conversion efficiency of lead free perovskite solar cells. First, a hot antisolvent treatment (HAT) was found to increase the film coverage and prevent electrical shunting in the photovoltaic device. Second, it was discovered that annealing under a low partial pressure of dimethyl sulfoxide vapor increased the average crystallite size. The topographical and electrical qualities of the perovskite films are substantively improved as a result of the combined treatments, facilitating the fabrication of tin‐based perovskite solar cell devices with power conversion efficiencies of over 7 %.     

n‐Type Conjugated Polymer Based on Dicyanodistyrylbenzene and Naphthalene Diimide Units for All‐Polymer Solar Cells

All polymer solar cells (all‐PSCs), possessing superior mechanical strength and flexibility, offer the commercialization opportunity of the PSCs for flexible and portable devices. In this work, we designed and synthesized two copolymer acceptors based on dicyanodistyrylbenzene (DCB) and naphthalene diimide (NDI) units. The corresponding copolymer acceptors are denoted as PDCB‐NDI812 and PDCB‐NDI1014. The medium band gap copolymer PBDB‐T was selected as donor material for investigation of the photovoltaic performance. Two all‐PSCs devices showed power conversion efficiencies (PCE) of 4.26% and 3.43% for PDCB‐NDI812 and PDCB‐NDI1014, respectively. The improved PCE was ascribed to the higher short‐circuit current (J_SC), greater charge carrier mobility and higher exciton dissociation probability of the PBDB‐T:PDCB‐NDI812 blend film. These results suggest that DCB unit and NDI unit based copolymer acceptors are promising candidates for high performance all‐PSCs.     

Textile‐Compatible Substrate Electrodes with Electrodeposited ZnO—A New Pathway to Textile‐Based Photovoltaics

A strategy is presented to realize textile‐based photovoltaic cells motivated by developments of textile‐based electronics and their demand of grid‐independent energy supply. Beyond this, a development of textile‐based photovoltaics also represents an attractive pathway towards very flexible and rugged solar cells. The need for compatibility of an appropriate photovoltaic technology with the physical limitations of textiles is stressed. Electrodeposition from aqueous solutions is presented as a successful strategy to realize semiconductor structures on textiles and detailed control and influence of the deposition conditions is discussed. The role of microelectrode effects, options of forced convection, deposition under pulsed potential, alternative deposition baths and different substrate metals are emphasized. An active electrode material is presented which reaches a conversion efficiency close to the 1 % limit under AM 1.5 illumination conditions and thereby opens the door for a further optimization towards devices of technical interest.     

Flexible,Stretchable, and Rechargeable Fiber‐Shaped Zinc–Air Battery Based on Cross‐Stacked Carbon Nanotube Sheets

The fabrication of flexible, stretchable and rechargeable devices with a high energy density is critical for next‐generation electronics. Herein, fiber‐shaped Zn–air batteries, are realized for the first time by designing aligned, cross‐stacked and porous carbon nanotube sheets simultaneously that behave as a gas diffusion layer, a catalyst layer, and a current collector. The combined remarkable electronic and mechanical properties of the aligned carbon nanotube sheets endow good electrochemical properties. They display excellent discharge and charge performances at a high current density of 2 A g⁻¹. They are also flexible and stretchable, which is particularly promising to power portable and wearable electronic devices.     

Flexible,Stretchable, and Rechargeable Fiber‐Shaped Zinc–Air Battery Based on Cross‐Stacked Carbon Nanotube Sheets

The fabrication of flexible, stretchable and rechargeable devices with a high energy density is critical for next‐generation electronics. Herein, fiber‐shaped Zn–air batteries, are realized for the first time by designing aligned, cross‐stacked and porous carbon nanotube sheets simultaneously that behave as a gas diffusion layer, a catalyst layer, and a current collector. The combined remarkable electronic and mechanical properties of the aligned carbon nanotube sheets endow good electrochemical properties. They display excellent discharge and charge performances at a high current density of 2 A g^?1. They are also flexible and stretchable, which is particularly promising to power portable and wearable electronic devices.