Application In Polymer Solar Cells Research Articles

Studies of Graphdiyne‐ZnO Nanocomposite Material and Application in Polymer Solar Cells

Graphdiyne‐ZnO (GDZO) composite material is prepared via a simple method and studied in detail for the first time. The transmission electron microscopy, Raman spectroscopy and X‐ray photoelectron spectroscopy (XPS) analyses confirm the formation of an adduct between GD and ZnO. Then the interaction between ZnO and GD is further investigated by first‐principles calculations. It is found that the Zn and O atom can coordinate bonding with GD, thus forming the CZn bond and CO bond, respectively. Polymer solar cells are fabricated based on the nanocomposites for the first time and an enhanced power conversion efficiency of 11.2%, compared with the devices with ZnO‐only (10%), is obtained. Simultaneously, the resultant devices show better stability, whether in glove box or in atmosphere, with humidity of 90%. The investigation of exciton generation rate, ideal current‐voltage model, and impedance spectra verify that the introduction of GDZO not only accelerates electron transfer but also reduces charge recombination occurring at the interface. The results indicate that GDZO is a promising electron transport material to enhance solar cell performance and presents a large potential for optoelectronic applications as well.

Engineering Two-Phase and Three-Phase Microstructures from Water-Based Dispersions of Nanoparticles for Eco-Friendly Polymer Solar Cell Applications

Nanoparticle organic photovoltaics, a subfield of organic photovoltaics (OPV), has attracted increasing interest in recent years due to the eco-friendly fabrication of solar modules afforded by colloidal ink technology. Importantly, using this approach it is now possible to engineer the microstructure of the light absorbing/charge generating layer of organic photovoltaics; decoupling film morphology from film deposition. In this study, single-component nanoparticles of poly(3-hexylthiophene) (P3HT) and phenyl-C61 butyric acid methyl ester (PC61BM) were synthesized and used to generate a two-phase microstructure with control over domain size prior to film deposition. Scanning transmission X-ray microscopy (STXM) and electron microscopy were used to characterize the thin film morphology. Uniquely, the measured microstructure was a direct input for a nanoscopic kinetic Monte Carlo (KMC) model allowing us to assess exciton transport properties that are experimentally inaccessible in these single-component par...

High-Performance Polymer Solar Cells Achieved by Introducing Side-Chain Heteroatom on Small-Molecule Electron Acceptor.

Side chains of photovoltaic materials play an important role in determining charge transport property, film morphology, and the corresponding device performance. In this work, two new acceptor materials, ATT-6 and ATT-7 with different side chains, m-hexylphenyl and m-hexyloxyphenyl on the indacenodithiophene, are designed and synthesized for applications in non-fullerene polymer solar cells. ATT-7 shows a higher absorption coefficient, increased crystallinity, and improved electron mobility in comparison with ATT-6. Using wide-bandgap polymer poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione)] (PBDB-T) as donor, optimized devices based on PBDB-T:ATT-7 and PBDB-T:ATT-6 delivers power conversion efficiencies of 10.30% and 8.39%, respectively. The higher performance of ATT-7-based device can be attributed to efficient exciton dissociation, reduced bimolecular recombination, and enhanced and balanced charge carrier mobilities. These results indicate that side-chain modification is an easy but efficient way in the design of high-performance non-fullerene acceptors.

Interaction of a Poly(phenylene vinylene) with an Organometallic Lewis Acid Additive: Fundamentals and Application in Polymer Solar Cells

The trimeric perfluoro-o-phenylene mercury compound Hg3 and poly(2-methoxy,5-(2′-ethylhexyloxy)-1,4-phenylenevinylene (MEH-PPV) interact strongly in solution and the solid state. The interaction is attributed to electron donor–acceptor complex formation, where MEH-PPV is the donor, and the Lewis acid Hg3 is the acceptor. The study reported herein explores the effects of the donor–acceptor complex formation on the properties of MEH-PPV in solution and in the solid state. Addition of Hg3 to MEH-PPV solution or films leads to a distinct color change, and the change in the visible absorption spectrum and fluorescence of MEH-PPV is consistent with the formation of polymer aggregates. In the solid state, Hg3 induced aggregation is suggested to lead to formation of crystalline domains of the conjugated polymer. Transmission electron microscopy and grazing incidence X-ray scattering results support the hypothesis that the complex formation with Hg3 induces aggregation of the polymer. Transient absorption spectros...

The influences of polyol process parameters on the optoelectronic characteristics of AgNWs-based flexible electrodes and their application in ITO-free polymer solar cells

Abstract Silver nanowires (AgNWs) have been considered as promising materials for fabrication of transparent conducting electrodes (TCEs) due to their suitable optical and electrical conductivity. The current work investigates the effects of the synthesis parameters on the physical and morphological properties of AgNWs-based TCEs and the photovoltaic performances of ITO-free AgNWs-electrode based flexible polymer solar cells (FPSCs). AgNWs were prepared using two different polyol-based methods including modified polyol (MP) and Sigma polyol (SP) processes. These methods differed in the type of applied seed, ratios of PVP/AgNO3 and AgNO3/seed, AgNO3 injection rate and temperature. The reflux condition was used as a novel effective parameter in the MP method. Results showed that MP-AgNWs possessed higher aspect ratio compared to those obtained from the SP process. AgNWs-based TCEs were prepared using spin coating method. The injection volume and the thickness of AgNWs-electrodes were altered to find the optimized electrodes in terms of sheet resistance (Rs) and transparency. The optimized MP-AgNWs and SP-AgNWs electrodes based on H-FoM calculations showed different Rs of 11.3 and 99.3 Ω.sq−1 and transparency of 92.8% and 90.4%, respectively. These electrodes were integrated as the photo-anode in the construction of ITO-free FPSCs. The prepared FPSCs based on the optimized MP-AgNWs electrodes showed PCE of 3.18% which was about 28% higher than that obtained using the best SP-AgNWs electrodes. The photovoltaic performance of MP-AgNWs electrode based FPSC was found to be very close to those of ITO-based reference cell prepared using similar conditions. However, the PCE of these FPSCs was about 18% lower which can be improved by altering the synthesis parameters.

Self-assembled monolayer modified copper(I) iodide hole transport layer for efficient polymer solar cells**Project supported by the National Natural Science Foundation of China (Grant Nos. 61377065 and 61574064), the Science and Technology Planning Project of Guangdong Province, China (Grant Nos. 2013CB040402009 and 2015B010132009), and the Science and Technology Project of Guangzhou City, China (Grant No. 2014J4100056).

The morphology of the copper iodide (CuI) film as an inorganic p-type material has an important influence on enhancing the performance of polymer solar cells (PSCs). A self-assembled monolayer of 3-aminopropanoic acid (C3-SAM) was used on the surface of indium tin oxide (ITO) before depositing the CuI films. Consequently, a well-distributed and smooth CuI film was formed with pinhole free and complete surface coverage. The root mean square of the corresponding CuI film was reduced from 3.63 nm for ITO/CuI to 0.77 nm. As a result, the average power conversion efficiency (PCE) of PSCs with the device structure of ITO/C3-SAM/CuI/P3HT:PC61BM/ZnO/Al increased significantly from 2.55% (best 2.66%) to 3.04% (best 3.20%) after C3-SAM treatment. This work provides an effective strategy to control the morphology of CuI films through interfacial modification and promotes its application in efficient PSCs.

Synthesis and studies of carbazole-based donor polymer for organic solar cell applications

We have developed a carbazole-based electron donor material, containing extended thiophene π-conjugated through a cyanovinylene spacer in order to enhance the effective intramolecular charge transfer for bulk heterojunction polymer solar cell (BHJ-PSC) applications. The polymer was synthesized via FeCl3 oxidative polymerization method, namely poly(2E,2′E)-3,3′-(9-hexyl-9H-carbazole-3,6-diyl)bis(2-(5-methylthiophen-2yl)acrylonitrile (CN-PICTAN). The CN-PICTAN formation was confirmed by Fourier transformed infrared, nuclear magnetic resonance spectroscopy, and gel permeation chromatography techniques. The CN-PICTAN showed a broad absorption and emission range with optical band gap (Egopt) of 2.1 eV. The CN-PICTAN exhibited a high thermal stability with 5% weight loss at 356 °C and deep-lying highest occupied molecular orbital level of − 5.23 eV. The BHJ-PSC device fabricated with CN-PICTAN:PC61BM (1:1.5) showed a power conversion efficiency of 1.23%, which was enhanced to 1.73% after the device was annealed at 100 °C.

Low-bandgap semiconducting polymers based on sulfur-containing phenacene-type molecules for transistor and solar cell applications

The incorporation of a highly extended π-electron system into a polymer backbone is an effective strategy to develop high-performance donor–acceptor (D–A) polymers suitable for organic electronics because this strategy can facilitate a dense π-π stacking structure, leading to efficient carrier transport. With this in mind, we developed phenanthro[1,2-b:8,7-b′]dithiophene (PDT) because this new phenacene-type molecule has a highly crystalline nature, deep HOMO level, and high hole mobility, which are characteristics known to be suitable for a donor unit in high-performance D–A polymers. In this focus review, we report recent progress in PDT-containing D-A polymers combined with various strong acceptor units. Incorporation of PDT into a polymer backbone results in deep HOMO energy levels of −5.4~−5.5 eV, strong aggregation, and a dense packing structure with a short π-stacking distance of 3.5~3.6 A. PDT-based polymers with appropriate alkyl side chains exhibit high hole mobilities of up to 0.18 cm2 V−1 s−1 in organic field-effect transistor (OFET) devices due to their tendency to form highly ordered edge-on structures. Furthermore, we can adjust their level of molecular orientation from edge-on to face-on by increasing their molecular weight, leading to a high power conversion efficiency of over 6% in polymer solar cell (PSC) applications. These results demonstrate that PDT is a good candidate as a high-performance building block in D-A polymers. A recent progress of phenanthro[1,2-b:8,7-b′]dithiophene (PDT)-based low bandgap semiconducting polymers combined with various strong acceptor units are described. By incorporating a highly π-extended PDT core into the polymer backbone, the synthesized polymers have deep HOMO energy levels and formed a dense packing structure with a short π-stacking distance. The PDT-based polymers with optimal side chains and high molecular weight exhibit high hole mobility of up to 0.18 cm−1 V−1 s−1 in organic field-effect transistors and high power conversion efficiency over 6%. These results indicate that PDT is a good π-framework as high-performance semiconducting polymers.

Effect of electron beam irradiation on polydopamine and its application in polymer solar cells

Effect of electron beam irradiation on polydopamine and its application in polymer solar cells

Facile Synthesis of the O-Functionalized Ladder-Type Dipyran Building Block and Its Application in Polymer Solar Cells.

A new centrosymmetrical dipyran unit (DTDP) is successfully prepared by means of an efficient and universal way, and a series of PDTDP polymers have been prepared so as to assess their potential application in organic photovoltaic. The function of pyran moiety is not merely limited to tune the electron-donating roles and energy levels but it also contributes to solubility improvement. Interestingly, all pyran-based polymers displayed wide absorption ranging from 350 to 780 nm, but varied aggregation phenomena are observed. Furthermore, the quantum chemistry calculations for dimers, morphology study and grazing-incidence wide-angle X-ray scattering analysis for blend films have been utilized to understand the variations at photovoltaic performances. Finally, PDTDP-4 achieved the highest power conversion efficiency of 7.26% ( Voc = 0.72 V, FF = 0.66, and Jsc = 15.30 mA/cm2), demonstrating promising usage for high-efficiency polymer donors in polymer solar cells. In all, not only a promising dipyran building block is provided by this study, more dipyran derivatives and polymers could be prepared via this facile synthetic route.

A narrow-bandgap donor polymer for highly efficient as-cast non-fullerene polymer solar cells with a high open circuit voltage

A new narrow-bandgap copolymer PBFTT, based on 4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene (BDT-2F) as donor unit and octyl-3-fluorothieno[3,4-b]thiophene-2-carboxylate (TT) as acceptor unit, was synthesized as donor material for non-fullerene (NF) polymer solar cells (PSCs) application. Compared to the analogue polymer PTB7-Th, PBFTT with two fluorine atoms in the conjugated side chains of BDT possesses a deeper HOMO energy level of −5.47 eV and a slightly enhanced hole mobility of 3.13 × 10−3 cm2 V-1 s-1 versus (vs.) a HOMO energy level of −5.30 eV and a hole mobility of 1.11 × 10−3 cm2 V-1 s-1 for PTB7-Th. Hence, the corresponding PSCs based on PBFTT:ITIC exhibited an optimal PCE of 9.1% with a Voc of 0.94 V, a Jsc of 16.0 mA cm−2, and a FF of 60.5% compared to a PCE of 6.8% with a Voc of 0.81 V, a Jsc of 14.2 mA cm−2 and a FF of 59.1% for PTB7-Th:ITIC-based PSCs. Notably, this PCE is among the highest values for the NF-PSCs based on narrow-bandgap polymer without extra treatments. These results indicate that PBFTT is a promising narrow-bandgap polymer donor material for NF-PSCs application.

A 2-(trifluoromethyl)thieno[3,4-b]thiophene-based small-molecule electron acceptor for polymer solar cell application

A new TbT unit 2-(trifluoromethyl)thieno[3,4-b]thiophene is designed and synthesized for developing small-molecule acceptor. A small molecule acceptor ATT-8 with an indacenodithiophene (ITD) core, two rhodanine ending-groups, and two TbT linkers were constructed. A wide-bandgap polymer donor PBDB-T is selected to fabricate bulk-heterojunction solar cells with ATT-8 acceptor. The as-cast film device delivers a PCE of 4.80% with an open circuit voltage (Voc) of 0.955 V, a short-circuit current (Jsc) of 10.32 mA cm−2 and a fill factor (FF) of 48.71%. Further optimization via additive and thermal annealing (TA) promotes PCE of the device to 7.31% with a Voc of 0.804 V, a Jsc of 13.90 mA cm−2, and an FF of 65.42%.

Recent Developments in Graphene/Polymer Nanocomposites for Application in Polymer Solar Cells.

Graphene (G) and its derivatives, graphene oxide (GO) and reduced graphene oxide (rGO) have enormous potential for energy applications owing to their 2D structure, large specific surface area, high electrical and thermal conductivity, optical transparency, and huge mechanical strength combined with inherent flexibility. The combination of G-based materials with polymers leads to new nanocomposites with enhanced structural and functional properties due to synergistic effects. This review briefly summarizes recent progress in the development of G/polymer nanocomposites for use in polymer solar cells (PSCs). These nanocomposites have been explored as transparent conducting electrodes (TCEs), active layers (ALs) and interfacial layers (IFLs) of PSCs. Photovoltaic parameters, such as the open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF) and power-conversion efficiency (PCE) are compared for different device structures. Finally, future perspectives are discussed.

A low cost and high performance polymer donor material for polymer solar cells

The application of polymer solar cells requires the realization of high efficiency, high stability, and low cost devices. Here we demonstrate a low-cost polymer donor poly[(thiophene)-alt-(6,7-difluoro-2-(2-hexyldecyloxy)quinoxaline)] (PTQ10), which is synthesized with high overall yield of 87.4% via only two-step reactions from cheap raw materials. More importantly, an impressive efficiency of 12.70% is obtained for the devices with PTQ10 as donor, and the efficiency of the inverted structured PTQ10-based device also reaches 12.13% (certificated to be 12.0%). Furthermore, the as-cast devices also demonstrate a high efficiency of 10.41% and the devices exhibit insensitivity of active layer thickness from 100 nm to 300 nm, which is conductive to the large area fabrication of the devices. In considering the advantages of low cost and high efficiency with thickness insensitivity, we believe that PTQ10 will be a promising polymer donor for commercial application of polymer solar cells.

Conjugated Polymers for Flexible Energy Harvesting and Storage.

Since the discovery of conjugated polymers in the 1970s, they have attracted considerable interest in light of their advantages of having a tunable bandgap, high electroactivity, high flexibility, and good processability compared to inorganic conducting materials. The above combined advantages make them promising for effective energy harvesting and storage, which have been widely studied in recent decades. Herein, the key advancements in the use of conjugated polymers for flexible energy harvesting and storage are reviewed. The synthesis, structure, and properties of conjugated polymers are first summarized. Then, their applications in flexible polymer solar cells, thermoelectric generators, supercapacitors, and lithium-ion batteries are described. The remaining challenges are then discussed to highlight the future direction in the development of conjugated polymers.

Self‐Doping Fullerene Electrolyte‐Based Electron Transport Layer for All‐Room‐Temperature‐Processed High‐Performance Flexible Polymer Solar Cells

AbstractTo achieve high‐performance large‐area flexible polymer solar cells (PSCs), one of the challenges is to develop new interface materials that possess a thermal‐annealing‐free process and thickness‐insensitive photovoltaic properties. Here, an n‐type self‐doping fullerene electrolyte, named PCBB‐3N‐3I, is developed as electron transporting layer (ETL) for the application in PSCs. PCBB‐3N‐3I ETL can be processed at room temperature, and shows excellent orthogonal solvent processability, substantially improved conductivity, and appropriate energy levels. PCBB‐3N‐3I ETL also functions as light‐harvesting acceptor in a bilayer solar cell, contributing to the overall device performance. As a result, the PCBB‐3N‐3I ETL‐based inverted PSCs with a PTB7‐Th:PC71BM photoactive layer demonstrate an enhanced power conversion efficiency (PCE) of 10.62% for rigid and 10.04% for flexible devices. Moreover, the device avoids a thermal annealing process and the photovoltaic properties are insensitive to the thickness of PCBB‐3N‐3I ETL, yielding a PCE of 9.32% for the device with thick PCBB‐3N‐3I ETL (61 nm). To the best of one's knowledge, the above performance yields the highest efficiencies for the flexible PSCs and thick ETL‐based PSCs reported so far. Importantly, the flexible PSCs with PCBB‐3N‐3I ETL also show robust bending durability that could pave the way for the future development of high‐performance flexible solar cells.

Enhancing the photovoltaic performance of bulk heterojunction polymer solar cells by adding Rhodamine B laser dye as co-sensitizer

Ternary blend (TB) strategy has been considered as an effective method to enhance the photovoltaic performance of bulk heterojunction (BHJ) polymer solar cells (PSCs). Here, we report on TB-based PSCs containing two donor materials; poly-3-hexylthiophene (P3HT) and Rhodamine B (RhB) laser organic dye, and [6,6]-phenyl C61 butyric acid methyl ester (PC61BM) as an acceptor. The influence of RhB weight percentage and injection volume was extensively studied. To gain insight into the influences of RhB on the photovoltaic performance of PSCs, physicochemical and optical properties of TBs were compared with those of BHJ binary blend as a standard. RhB broadened the light absorption properties of the active layer and played a bridging role between P3HT and PC61BM. The PCE and short-circuit current density (Jsc) of the optimized TB-based PSCs comprising of 0.5 wt% RhB reached 5% and 12.12 mA/cm2, respectively. Compared to BHJ standard cell, the PCE and the generated current was improved by two orders of magnitude due to higher photon harvest of the active layer, cascade energy level structure of TB components and a considerable decrease in the charge carrier recombination. The results suggest that RhB can be considered as an effective material for application in PSCs to attain high photovoltaic performance.

A simple strategy to achieve shape control of Au-Cu2-xS colloidal heterostructured nanocrystals and their preliminary use in organic photovoltaics.

Au-Cu2-xS Janus nanostructures with a shape-controlled semiconductor part are successfully built. The key parameters for controlling the morphology of Cu2-xS in Au-Cu2-xS are demonstrated. Coupled local surface plasmon resonance (LSPR) properties in these Au-Cu2-xS NCs give them potential for application in polymer solar cells (PSCs) as an efficient dopant.

Synthesis of hexamethylene diisocyanate-functionalized graphene oxide for solar cell applications

Graphene (G), an allotrope of carbon with exceptional optical, electronic, thermal and mechanical properties, and its oxidized form graphene oxide (GO), show huge potential for a broad range of applications. In particular, their high conductivity, transparency, flexibility, and abundance make them suitable for polymer solar cells (PSCs). However, their insolubility in common organic solvents hinders their applications. Consequently, novel functionalization approaches are pursued. The present work is devoted to the preparation of hexamethylene diisocyante-functionalized graphene oxide (HDI-GO). The synthesized nanomaterial shows a highly hydrophobic nature and can be dispersed in organic non-polar solvents, hence is a prospective candidate to be combined with conjugated polymers for solar cell applications.

Investigation of precursor solution concentration effect on morphology and optical properties of zinc oxide nanorods for polymer solar cells application

Investigation of precursor solution concentration effect on morphology and optical properties of zinc oxide nanorods for polymer solar cells application