Application In Polymer Solar Cells Research Articles

Development of cross-linked donor polymers for polymer solar cells with improved efficiency and thermal stability

Due to low glass-transition temperature and high diffusion coefficient of small molecule acceptors (SMAs), the bi-continuous interpenetrating morphology of SMA-based polymer solar cells (PSCs) are metastable and therefore most SMA-based PSCs exhibit poor operational and thermal stability. Cross-linked donor polymers have been proposed because the cross-linked behavior can “freeze” the initial morphology and avoid its further evolution. In this work, two new cross-linked donor polymers P1 and P2 were designed for application in PSCs with a non-fullerene acceptor Y6, in which the photovoltaic performance and thermal stability of PSCs were significantly improved. The P1-based PSCs achieved a superior power conversion efficiency (PCE) of 17.29 % with a Jsc of 25.99 mA cm−2, a Voc of 0.860 V and a FF of 77.35 %, which surpassed 9 % for PM6-based PSCs (15.86 %). Furthermore, the P1-based PSCs exhibited better thermal stability with a 17 % efficiency loss under continuous 60 °C for 210 h due to the fixation of active layer morphology, while PM6-based PSCs suffered from a serve PCE reduction of over 26 %. These results demonstrate that cross-linked donor polymer has a great application prospect to improve the PCE and thermal stability of PSCs.

Cost-effective polymer donors based on pyridine for efficient nonfullerene polymer solar cells

Developing cost-effective polymer donors that can match nonfullerene acceptors is very important for practical applications of polymer solar cells (PSCs). In this work, low-cost 3-fluoropyridine and pyridine were employed as acceptor unit cores to construct cost-effective polymers PBDT-FPy, PBDT-Py and PBDF-Py by copolymerizing with commercially available donor units. PBDT-FPy, PBDT-Py and PBDF-Py show wide-bandgap of 2.08, 2.15 and 2.05 eV, respectively. Due to the strong electronegativity of nitrogen atom in pyridine and Nδ− … Hδ+ noncovalent dipole-dipole interactions, all polymers exhibit deep-lying highest-occupied molecular orbital (HOMO) energy levels, strong intermolecular π-π interaction and good planarity. The PBDT-FPy: Y6 based device exhibits a power conversion efficiency (PCE) of 8.34%, while the performance of PBDT-Py: Y6 and PBDF-Py: Y6 devices was significantly improved, with PCE of 10.02% and 10.00%. The results indicate that pyridine with simple structure and low synthetic cost is a promising building block to construct high-performance cost-effective polymer donors for application in PSCs.

Novel Polyelectrolytes Based on Naphthalene Diimide with Different Counteranions for Cathode Interlayers in Polymer Solar Cells.

We synthesized novel polyelectrolytes based on naphthalene diimide with quaternary amine featuring hydroxyl groups at the side chain, along with different counteranions (PF-NDIN-Br-OH and PF-NDIN-I-OH) for polymer solar cell (PSC) application as the interlayer. The polyelectrolytes establish a beneficial interface dipole through the ionic moieties and synergistic effects arising from the hydroxyl groups located at the side chain. Incorporating polyelectrolytes as the cathode interlayer resulted in an enhancement of the power conversion efficiency (PCE). The PCE of the device with PF-NDIN-Br-OH increased from 8.96% to 9.51% compared to the ZnO-only device. The best PCE was obtained with the device based on PF-NDIN-I-OH, up to 9.59% resulting from the Jsc enhancement. This outcome implies a correlation between the performance of the device and the synergistic effects observed in polyelectrolytes containing hydroxyl groups in the side chain, along with larger anions when employed in PSCs.

Enabling Highly Efficient and Thermal-Stable Polymer Solar Cells through Semi-Alloy Acceptors Composed of a Hinge-Like Dimer: A Versatile Doping Protocol.

The simultaneous improvement of power conversion efficiency (PCE) and thermal stability is a critical scientific challenge in advancing the commercial applications of polymer solar cells. To address this challenge, a dumbbell-shaped dimeric acceptor, DT19, is successfully designed and synthesized. It is incorporated as a third component into the PM1:BTP-eC9 system. This ternary strategy demonstrates a synergistic enhancement of the PCE and thermal stability of the host binary system. In particular, the PM1:BTP-eC9:DT19 system maintains a PCE of over 90% even after heating at 120°C for 200h. Additionally, the dimer-doping ternary strategy exhibits excellent generality for the other four Y-series systems and outperforms ternary systems containing alloy-like acceptors in terms of thermal stability. It is because DT19, with its hinge-like structure, can form a semi-alloy acceptor with the host acceptor, leading to strong interchain entanglement with the polymer donor, thus overcoming phase separation and excessive aggregation under thermal stress. This new type of dimeric material, which can synergistically enhance the device efficiency and thermal stability of active layers, presents promising application prospects.

Poly(dimethylsiloxane)-block-PM6 Polymer Donors for High-Performance and Mechanically Robust Polymer Solar Cells.

High power conversion efficiency (PCE) and stretchability are the dual requirements for the wearable application of polymer solar cells (PSCs). However, most efficient photoactive films are mechanically brittle. In this work, highly efficient (PCE = 18%) and mechanically robust (crack-onset strain (COS) = 18%) PSCs are acheived by designing block copolymer (BCP) donors, PM6-b-PDMSx (x = 5k, 12k, and 19k). In these BCP donors, stretchable poly(dimethylsiloxane) (PDMS) blocks are covalently linked with the PM6 blocks to effectively increase the stretchability. The stretchability of the BCP donors increases with a longer PDMS block, and PM6-b-PDMS19k :L8-BO PSC exhibits a high PCE (18%) and 9-times higher COS value (18%) compared to that (COS = 2%) of the PM6:L8-BO-based PSC. However, the PM6:L8-BO:PDMS12k ternary blend shows inferior PCE (5%) and COS (1%) due to the macrophase separation between PDMS and active components. In the intrinsically stretchable PSC, the PM6-b-PDMS19k :L8-BO blend exhibits significantly greater mechanical stability PCE80% ((80% of the initial PCE) at 36% strain) than those of the PM6:L8-BO blend (PCE80% at 12% strain) and the PM6:L8-BO:PDMS ternary blend (PCE80% at 4% strain). This study suggests an effective design strategy of BCP PD to achieve stretchable and efficient PSCs.

One-dimensional ternary conducting polymers blend with 9.26% power conversion efficiency for photovoltaic devices applications

HCl doped-copolymer of ortho phenylene diamine, meta phenylene diamine, and pyrrole terpolymers blend was synthesized. Physical vapor deposition was used to produce the terpolymer-blended thin films, allowing the creation of the fiber structure at a low deposition rate, with a chamber pressure of 5 × 10−5 mbar and a thickness of 100 ± 2 nm. The produced thin films of terpolymers blend were examined utilizing a combination of theoretical and experimental techniques including TD-DFT/DMol3, CATSTEP, FT-IR spectrum, XRD, and optical characterizations. According to XRD computations, the terpolymers blend had an average crystallite size of 190 ± 2 nm, while SEM measurements showed that the length of the fibers was ≅ 73 ± 2 μm. The blend of terpolymers displayed an absorbance of 1.83 at 612 nm. Additionally, the blend of terpolymers' indirect/direct bandgap and absorption index was observed with noticeable alterations. The molecular structure optimization and frequency calculations for the crystal models and isolated molecules were carried out using the materials studio 7.0 tool (TDDFT/DMol3 and CASTEP). The DFT-Gaussian09W-vibration values closely matched the experimental results in terms of structure and optical characteristics. The application of thin films in polymer solar cell applications looks promising due to the noticeable improvements in optical characteristics.

Low-cost synthesis of small molecule acceptors makes polymer solar cells commercially viable

The acceptor-donor-acceptor (A–D–A) or A–DA’D–A structured small molecule acceptors (SMAs) have triggered substantial progress for polymer solar cells (PSCs). However, the high−cost of the SMAs impedes the commercial viability of such renewable energy, as their synthesis via the classical pyridine-catalyzed Knoevenagel condensation usually suffers from low reaction efficiency and tedious purifying work-up. Herein, we developed a simple and cheap boron trifluoride etherate-catalyzed Knoevenagel condensation for addressing this challenge, and found that the coupling of the aldehyde-terminated D unit and the A-end groups could be quantitatively finished in the presence of acetic anhydride within 15 minutes at room temperature. Compared with the conventional method, the high reaction efficiency of our method is related to the germinal diacetate pathway that is thermodynamically favorable to give the final products. For those high performing SMAs (such as ITIC-4F and Y6), the cost could be reduced by 50% compared with conventional preparation. In addition to the application in PSCs, our synthetic approach provides a facile and low-cost access to a wide range of D–A organic semiconductors for emerging technologies.

Purification of nitrogen-doped graphene quantum dots and its application in polymer solar cells

Nitrogen-doped graphene quantum dots (N-GQDs) have potential application in photovoltaic devices because of their adjustable bandgap and remarkable dispersion in amphiphilic systems. In this study, N-GQDs were synthesized and purified, and changes in their optical properties before and after purification were compared. The introduction of the N-GQDs into the ZnO electron transport layer (ETL) of a bulk heterojunction polymer solar cell based on PTB7:PC71BM enhanced the power conversion efficiency (PCE) significantly. Purified N-GQDs showed stronger N doping, obvious blue shift of photoluminescence (PL) emission, and improved dispersion in organic system. After chloroform extraction and purification, the N-GQDs derived from citric acid-urea ethanol solution had the least loss and the most prominent optical performance (quantum yield =41.95%). The purified N-GQDs showed longer fluorescence lifetime than that before purification and still showed strong PL performance after compounding with ZnO ETL. N-GQDs modified ZnO ETL layer has stronger light transmittance and lower impedance. The stronger light transmittance is capable of improving the light absorption of the active layer while the lower impedance can promote electron transfer. Both properties are conductive to the PCE.

18.55% Efficiency Polymer Solar Cells Based on a Small Molecule Acceptor with Alkylthienyl Outer Side Chains and a Low-Cost Polymer Donor PTQ10

18.55% Efficiency Polymer Solar Cells Based on a Small Molecule Acceptor with Alkylthienyl Outer Side Chains and a Low-Cost Polymer Donor PTQ10

Donor–Acceptor Copolymers with Rationally Regulated Side Chain Orientation for Polymer Solar Cells Processed by Non-Halogenated Solvent

A donor–acceptor (D-A) conjugated polymer PBTFO-T-1 consisting of 2,1,3-benzothiadiazole (BT) as A unit and thiophene (T) as D unit was facilely obtained by a straightforward three-step reaction. The BT unit is attached with a fluorine atom and an alkoxy chain to simultaneously endow the polymer with a deep HOMO energy level and desirable solubility. The alkoxyl chain orientation on the BT unit has been regulated and the polymer PBTFO-T-2 with regio-regularly oriented side chains was also developed to investigate the impact of the alkoxyl chain orientation on their optoelectronic properties. The PBTFO-T-1:Y6-BO polymer solar cells (PSCs) were processed with a non-halogenated solvent and achieved an optimized power conversion efficiency of 14.16%, significantly higher than 9.39% of the PBTFO-T-2:Y6-BO counterpart. It has been demonstrated that the PBTFO-T-1:Y6-BO film exhibits higher and more balanced charge transportation and superior film morphology, resulting in higher exciton generation and dissociation, less recombination and eventually the higher short-circuit current density (J sc) and fill factor. This study provides a possible strategy to develop polymer donors with low cost for future commercial applications of PSCs and gives some insights into regulating optoelectronic properties of polymer donors via rationally modifying their side chain orientation.

Synthesis of D‐A copolymers based on thiadiazole and thiazolothiazole acceptor units and their applications in ternary polymer solar cells

AbstractWe have designed and synthesized two wide bandgap new donor‐acceptor (D‐A) copolymers consisting of the same alkylthiazole‐substituted benzo[1,2‐b;4,5‐b′]dithiophene (BDTTz) donor unit and but different acceptor units, i.e., thiazolo[5,4‐d]thiazole (TTZ) (P122) and 1,3,‐4 thiadiazole (TDz) (P123) and investigated their optical and electrochemical properties. We have employed these copolymers as donor and fullerene (PC71BM) and narrow bandgap non‐fullerene (Y6) as acceptor, to fabricate binary and ternary bulk heterojunction polymer solar cells (PSCs). The overall power conversion efficiency (PCE) of optimized binary bulk heterojunction PSCs based on P122:Y6 and P123:Y6 is 12.60% and 13.16%, respectively. The higher PCE for PSCs based on P123 than P122 counterparts may be associated with the broader absorption profile of the P123 and more charge carrier mobilities than that for the P122 active layer. With the incorporation of small amount of PC71BM into either P122:Y6 or P123:Y6 binary blend, the corresponding ternary PSCs showed an overall PCE of 14.89% and 15.52%, respectively, which is higher than the binary counterparts using either Y6 or PC71BM as acceptor. Incorporating the PC71BM in the binary host blend increases the absorption in the 300–500 nm wavelength region, generating more excitons in the active ternary layer and helping to dissociate the excitons into free charge carriers more effectively. The more appropriate nanoscale phase separation in the active ternary layer than the binary counterpart may be one of the reasons for higher PCE.

High-performance one and two-dimensional doped polypyrrole nanostructure for polymer solar cells applications

High-performance one and two-dimensional doped polypyrrole nanostructure for polymer solar cells applications

Synthesis and characterization of chiral nano-poly [(±)-2-sec-butyl aniline] and its application in the first chiral polymer solar cell

Recently, there has been tremendous advancement in the development of polymer solar cells. Polymer solar cells have attracted a great deal of attention because of their environmental stability, excellent thermal stability, and inexpensive. This study focuses on the synthesis of racemic chiral alkyl-substituted of PANI derivative in nanoscale, poly [(±)-2-sec-butyl aniline] (PSBA), and its applications for chiral polymer solar cells. In this polymer photovoltaic device, a chiral polymer layer is used as the active layer. In fact, this is the first chiral polymer solar cell that has many other advantages such as simple structure (single layer), ease of construction, lower manufacturing cost, green synthesis condition, and high stability.

Perylene Diimide-Based Oligomers and Polymers for Organic Optoelectronics

ConspectusPerylene diimide (PDI) as a classical dye has some advantages, such as structural diversity, tunable optical and electronic properties, strong light absorption, high electron affinity, and good electron-transporting properties and stability. The PDI-based oligomers and polymers are good candidates for n-type semiconductors in organic electronics and photonic devices.A polymer solar cell (PSC) that converts sunlight into electricity is a promising renewable and clean energy technology and has some superiorities, such as simple preparation and being lightweight, low cost, semitransparent, and flexible. For a long time, fullerene derivatives (e.g., PCBM) have been the most important electron acceptors used in the active layer of PSCs. However, PCBM suffers from some disadvantages, for example, weak absorption, a large amount of energy loss, and unstable morphology. Compared to PCBM, PDI-based materials present some advantages: intense visible-light absorption; lowest unoccupied molecular orbital (LUMO) energy levels can be modulated to achieve a suitable charge separation driving force and high open-circuit voltage (VOC); and the molecular configuration can be adjusted to achieve morphology stability. Thus, PDI-based oligomers and polymers are widely used as electron acceptors in the active layer of PSCs. In addition, PDI-based oligomers and polymers are widely used as n-type semiconductors in other electronic and photonic devices, such as organic field-effect transistors (OFETs), light-emitting diodes, lasers, optical switches, and photodetectors.In this Account, we present a brief survey of the developments in PDI-based oligomers and polymers and their applications in organic electronic and photonic devices, especially in solar cells and field-effect transistors. Although parent PDI dyes exhibit strong absorption, large electron affinity, and high electron mobility, the initial bulk-heterojunction PSCs based on PDI acceptors yielded a very low power conversion efficiency (ca. 0.1%). The highly planar configuration of parent PDI causes strong intermolecular π–π stacking, large crystalline domains, and severe donor/acceptor (D/A) phase separation, leading to a low exciton dissociation efficiency and poor device performance. Starting in 2007, our group designed linear-shaped PDI dimers with different bridges, star-shaped PDI trimers, and PDI polymers to overcome excess crystallization and PDI aggregation and to achieve appropriate D/A miscibility and phase separation. Molecular design strategies were developed to promote the planarity of the backbone and down-shifted LUMO level of PDI polymers, which is beneficial for strong intermolecular π–π stacking, high mobility, and good air stability of OFETs. Beyond PSC and OFET applications, PDI polymers can also be used in perovskite solar cells and two-photon absorption. Future research directions toward the performance optimization of PDI oligomers and polymers are also proposed.

Magneto-electrical properties of nickel phthalocyanine thin film and its application in organic solar cells

The nickel phthalocyanine (NiPc) thin film has been explored for magneto-conductance and optoelectrical properties. The surface morphology and the opto-electrical properties of thin films of NiPc have been observed as a good candidate for the applications in polymer solar cells. The AFM images show an almost continuous surface over the studied area. The spin interaction, the disordering of the spins part, and their suitable models have been discussed by the magneto-conductance properties of the thin films. The relaxation time of carriers and traps filling phenomena with applied bias are discussed by the impedance spectroscopy. The thin films of NiPc have been introduced as a hole interface buffer layer in the standard structure of P3HT: PCBM solar cells. The power conversion efficiency (PCE) of the optimized solar cell with NiPc is ∼3.17% and the fill factor (FF) is ∼69%., these device parameters are higher (PCE increased by ∼65% and FF by ∼39%) as compared to the organic solar cells fabricated without NiPc thin films in the same batch. The improved performance of organic solar cells attributed due to lowering the series and shunt resistance.

ZnO:Bio-inspired polydopamine functionalized Ti3C2Tx composite electron transport layers for highly efficient polymer solar cells

The optimized electron transport layer (ETL) plays a crucial role in the practical application of polymer solar cells (PSCs). Herein, bio-inspired polydopamine (PDA) modified Ti3C2Tx (PDA-Ti3C2Tx) as a multifunctional additive is dispersed into ZnO to fabricate ZnO:PDA-Ti3C2Tx composite ETL. PDA-Ti3C2Tx passivates the trap states of ZnO via forming strong and stable chelate interactions through Zn2+ ions and PDA molecules. PDA-Ti3C2Tx also lowers the vacuum level of transport layer by forming interface dipoles between catechol of PDA and Zn2+ ions of zinc oxide. Moreover, PDA-Ti3C2Tx constructs additional electron transport pathways by connecting the discontinuities among ZnO nanocrystals. As such, ZnO:PDA-Ti3C2Tx composite ETL, with higher conductivity and proper work function, can effectively collect electrons in the PSCs. Compared with ZnO control devices, the performance of PSCs with ZnO:PDA-Ti3C2Tx ETL is obviously enhanced with power conversion efficiencies (PCEs) from 10.34% to 12.07% based on PBDB-T:ITIC, 14.84–16.69% based on PM6:Y6, and 8.14–9.41% for PTB7:PC71BM, respectively. The ambient stability of the PSCs with ZnO:PDA-Ti3C2Tx ETLs is significantly improved due to the increased hydrophobicity of ETL and the enhanced crystallinity of active layer. The novel ETLs provide a facile, eco-friendly, low-cost approach to realize the highly performance and stable PSCs.

Strategic surface modification of ZnO interlayer for optimizing power conversion efficiency of solar cells based on quinoxaline-based polymer

A new quinoxaline-based conjugated donor polymer (PQTBDT), comprising an electron-donating benzodithiophene unit and electron-accepting cyanoquinoxaline was synthesized for bulk heterojunction-type polymer solar cell applications. The effects of morphology and solvent treatment of ZnO interlayer on the photovoltaic properties of PQTBDT-based PSCs were investigated through systemic characterization of morphology, UV–Vis absorption, transmittance, and charge recombination properties. Nano-ripple-structured ZnO electron transport layer enhanced both charge extraction capability and short circuit current density by enlarged interface contact area and light trapping effect, respectively. Additional solvent treatment using ethanolamine further reduced interface charge traps, resulting in higher shunt resistance compared to the devices based on planar ZnO layer. Combination of these two processes for ZnO interlayer optimized performance of PQTBDT-based solar cells with power conversion efficiency up to 6.50%.

Simple and green route for fabrication of a nanostructured of the graphene‐Fe3O4@PANI for the photovoltaic activity

In this work, for the first time, Gr (graphene)|Fe3O4@PANI nanocomposite was synthesized from graphite, aniline-HCl and FeCl3.6H2O via a simple in-situ and green route as the active layer for photovoltaic application. The proposed nanocomposite was characterized by FT-IR, SEM, TEM, UV-vis spectroscopy, XRD technique, and then the thermal, magnetic, electrochemical, and photovoltaic properties investigated. The energy gap was calculated, and it is noticed that the optical band gap of nanocomposite fallows an indirect transition, arising from a strong spin-orbit coupling created by Fe3O4 in the Gr|Fe3O4@PANI nanocomposite. Next, polymer solar cell (PSC) based on this nanocomposite was fabricated with a simple device structure of FTO│TiO2│Gr|Fe3O4@PANI│Al. The photovoltaic properties of the cells have been evaluated under AM 1.5G illumination at 60 mW/cm2 with a solar simulator. A power conversion efficiency (PCE) of 1.81% was observed with a short circuit current (Jsc) of 4.14 mA/cm2, an open-circuit voltage (Voc) of 0.71 V, which indicates this kind of conjugated polymer should be a promising material in the application of polymer solar cells.

Vertical Distribution in Inverted Nonfullerene Polymer Solar Cells by Layer‐by‐Layer Solution Fabrication Process

The layer‐by‐layer (LBL) solution process is a potential technology for future application of polymer solar cells (PSCs), while the vertical composition distribution evolution of the LBL active layer is still unknown. In this work, taking advantage of the LBL method and inverted device structure, inverted LBL‐processed PSCs are fabricated with polymer donor PM6 and nonfullerene small‐molecule acceptor Y6. As‐prepared devices with PM6 as the bottom layer and Y6 as the top layer exhibit low power conversion efficiencies (PCEs), while the post‐treatment brings a significant boost on the device performance (from 8.5% to 14.4%). The vertical composition distribution evolution of LBL photoactive layer is investigated by the combination of surface atom distribution analysis via X‐ray photoemission spectroscopy (XPS) and composition distribution across the bulk of the films via neutron reflectivity (NR). The findings can potentially offer positive guidance for the further utilization of organic photovoltaics.

A dithienobenzothiadiazole-quaterthiophene wide bandgap polymer enables non-fullerene based polymer solar cells with over 15% efficiency

In this work, a wide bandgap (WBG) polymer donor PDTfBT-4T based on dithienobenzothiadiazole (DTfBT) and quaterthiophene (4T) was synthesized for the application in non-fullerene polymer solar cells (PSCs). Polymer PDTfBT-4T showed film absorption peak at 554 nm and optical band gap of 1.93 eV. Complementary absorption and sufficiently energetic offsets could be achieved between the PDTfBT-4T and a benzotriazole-fused Y-series non-fullerene acceptor Y14. The PDTfBT-4T:Y14 active layer could deliver an open-circuit voltage of 0.83 V, a short-circuit current density of 25.42 mA cm−2, and a fill factor of 72.0%, corresponding to a power conversion efficiency (PCE) of 15.19%. This is the highest efficiency among WBG polymer donors based on an electron-deficient unit and an oligothiophene, which is also significantly higher than those of the fluorinated or esterified polythiophenes. The results indicate that DTfBT is a powerful electron-deficient unit, which is promising in the construction of simple WBG polymer donors for efficient NFA based PSCs.