Development Of Polymer Solar Cells Research Articles

Improvement of photovoltaic properties of benzo[1,2-b:4,5-b′]difuran-conjugated polymer by side-chain modification

The development of polymer solar cells (PSCs) for the donor materials based on benzo[1,2-b:4,5-b′]dithiophene (BDT) has significantly boosted the power conversion efficiency (PCE). However, the PCE of polymer donor materials for benzo[1,2-b:4,5-b′]difuran (BDF)-based lags far behind that of their BDT analogs. To further explore efficient copolymers based on BDF units, a two-dimensional (2D) side-chain strategy was proposed to investigate the atom-changing effects on the copolymer donors for the properties of electron and optical. In this study, we designed and synthesized three new BDF-based copolymer donor materials, named PBDF-C, PBDF-O, and PBDF-S. Owing to the balanced charge transport and favorable phase separation of PBDF-S:Y6, a high PCE of 13.4%, a short-circuit current ( J sc ) of 25.48 mA cm −2 , an open-circuit voltage ( V oc ) of 0.721 V, and a fill factor (FF) of 72.6% was obtained. This research demonstrates that the BDF building block has great potential for constructing conjugated copolymer donors for high-performance PSCs and that 2D side-chain modification is a facile approach for designing high-performance BDF-based copolymer materials.

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.

Smart Ternary Strategy in Promoting the Performance of Polymer Solar Cells Based on Bulk-Heterojunction or Layer-By-Layer Structure.

Although the rapid development of polymer solar cells (PSCs) has been achieved, it is still a great challenge to explore efficient ways for improving power conversion efficiency (PCE) of PSCs from materials and device engineering. Ternary strategy has been confirmed as an efficient way to improve PCE of PSCs by employing three kinds of materials. In this work, one polymer donor PM6, and two non-fullerene materials N3 and MF1 are selected to prepare ternary PSCs with layer-by-layer (LbL) or bulk-heterojunction (BHJ) structure. The LbL and BHJ-PSCs exhibit PCEs of 16.75% and 16.76% with 15wt% MF1 content in acceptors, corresponding to over 5% or 4% PCE improvement compared with N3-based binary PSCs with LbL or BHJ structure. The PCE improvement is mainly attributed to the fill factor enhancement from 73.29% to 76.95% for LbL-PSCs or from 74.13% to 77.51% for BHJ-PSCs by employing the ternary strategy. This work indicates that ternary strategy has great potential in preparing highly efficient LbL-PSCs via simultaneously optimizing molecular arrangement and the thickness of each layer.

Two dependent working mechanisms enables efficient ternary polymer solar cells with broad compositional tolerance

Decades of rapid development of polymer solar cells, more and more researchers shift from the direction of pursuing higher power conversion efficiency (PCE) to investigate the properties that satisfy the future commercialization processing conditions. In this work, an efficient D1:D2:A nonfullerene ternary polymer solar cells (PSCs) was fabricated by introducing PM6 in PBTA-PS:ITIC system. With complementary light absorption, structure compatibility, more favorable face-on orientation, optimized morphology and tuned energy levels, the ternary PSCs achieve an enhanced PCE of 11.91% with enhanced short circuit current density (JSC) of 18.58 mA cm−2 and fill factor (FF) of 67.70%, which are higher than that of binary solar cells. It is useful to mention that the ternary devices exhibit with broad compositional tolerance and device stability, which satisfy the large-scale commercialization fabrication conditions. After systematically analysis, two dependent working mechanisms are illustrated in the ternary devices, including FRET channel and charge transfer channel, which benefit the energy transfer and excitons dissociation. Therefore, this work demonstrated a facile method to fabricate efficient two donors ternary PSCs with broad compositional tolerance, higher stability and two dependent working mechanisms, which further promote the commercialization of PSCs.

Over 15% efficiency all-small-molecule organic solar cells enabled by a C-shaped small molecule donor with tailorable asymmetric backbone

Abstract In the past few years, compared with the rapid development of polymer solar cells (PSCs), the research progress of all-small-molecule organic solar cells (ASM-OSCs) lags far behind. Herein, two kinds of C-shaped SM donors named FBD-S3 and TBD-S4, bearing subtly tailorable asymmetric central core, are firstly reported. Both the two SMs show broad as well as matched absorption and energy level with classical acceptor Y6. The introduction of asymmetric core endows SM with Y6-similar bending skeleton and a unique network assembly in which the SM donor can easily interpenetrate into neighboring Y6 via strong intermolecular interaction and facile stacking direction. These features would hinder rapid aggregation and prevent to form large domains of single component in blends, resulting in an extraordinary power conversion efficiency of 15.10% in TBD-S4:Y6-based device, which is one of the highest values for ASM-OSCs. In addition, our comparative study demonstrates that although the donor material TBD-S4 exhibits reduced crystallinity, such a molecule matches better with acceptor Y6 and works more efficiently for ASM-OSCs. This work indicates that conformation tailorable by asymmetric central core is a novel and powerful method to design SM donor, which open a new avenue for highly efficient ASM-OSCs.

Naphtho[2,3-c]thiophene-4,9-dione based polymers for efficient fullerene solar cells

Designing and synthesizing new organic photovoltaic materials is an inexhaustible driving force for the development of polymer solar cells (PSCs). For an excellent molecular structure with a certain conjugated skeleton, studying its analogues is of considerable significance for fully exploiting its photovoltaic potential. In this work, naphtho[2,3-c]thiophene-4,9-dione (NTD), an analogue of benzo [1,2-c:4,5-c’]dithiophene-4,8-dione (BDD), was designed and synthesized. Based on this building block, alkoxy side chains and alkylthio side chains were grafted on NTD to build NTD-O and NTD-S unit respectively, and then two new D-A conjugated donor polymers, PBNO and PBNS, were synthesized with NTD-O and NTD-S units as acceptor units and asymmetric benzodithiophene unit (asy-BDTBP) as donor units. Later, the photoelectric properties of these two materials in fullerene PSCs were studied. Compared with BDD based benzodithiophene copolymer (asy-BDTBP-BDD), PBNO and PBNS show similar LUMO energy levels, −3.59 eV and −3.63 eV, respectively, PBNO and PBNS show higher HOMO energy levels, which are −5.25 eV and −5.37 eV, respectively. PBNO blended with fullerene acceptor PC71BM exhibited similar power conversion efficiency (PCE) compared to the copolymer asy-BDTBP-BDD (4.64%). The PCE is 4.71% with short-circuit current density (JSC) of 9.85 mA cm−2, open-circuit voltage (VOC) of 0.784 V and fill factor (FF) of 60.98%. Encouragingly, PBNS presented an obviously enhanced PCE in PC71BM system PSCs, and PCE boosted to 7.58% (JSC, 12.40 mA cm−2; VOC, 0.865 V; FF, 70.83%). This work shows that analogues of excellent molecules have huge photovoltaic potential, and that side-chain modification has a significant impact on improving the photovoltaic performance of PSCs.

13.7% Efficiency Small-Molecule Solar Cells Enabled by a Combination of Material and Morphology Optimization.

Compared with the quick development of polymer solar cells, achieving high-efficiency small-molecule solar cells (SMSCs) remains highly challenging, as they are limited by the lack of matched materials and morphology control to a great extent. Herein, two small molecules, BSFTR and Y6, which possess broad as well as matched absorption and energy levels, are applied in SMSCs. Morphology optimization with sequential solvent vapor and thermal annealing makes their blend films show proper crystallinity, balanced and high mobilities, and favorable phase separation, which is conducive for exciton dissociation, charge transport, and extraction. These contribute to a remarkable power conversion efficiency up to 13.69% with an open-circuit voltage of 0.85 V, a high short-circuit current of 23.16 mA cm-2 and a fill factor of 69.66%, which is the highest value among binary SMSCs ever reported. This result indicates that a combination of materials with matched photoelectric properties and subtle morphology control is the inevitable route to high-performance SMSCs.

Energy levels modulation of small molecule acceptors for polymer solar cells

Non-fullerene acceptor exhibits very promising prospect for the development of polymer solar cells (PSCs). It is necessary to carefully investigate the energy level matching between donor and acceptor to optimize the photovoltaic performance. In this paper, we have designed and synthesized two novel planar A-D-A type small molecular acceptors of IDT-RCN and IDT-CA with 2-(1,1-dicyanomethylene)rhodanine and cyanoacetate as the end groups, respectively. Compared to IDT-RCN with stronger electron-deficient end group, IDT-CA displayed 0.15 eV increase in LUMO level while almost the same HOMO level. PSC devices based on P3HT:IDT-CA show a power conversion efficiency (PCE) of 4.19% with VOC of 0.84 V, JSC of 7.77 mA cm−2 and FF of 0.64, which is much higher than that of P3HT:IDT-RCN mainly due to the higher VOC value. This work indicates that end group modification is important for the modulation of PSC device parameters.

Toward Solution-Processed High-Performance Polymer Solar Cells: from Material Design to Device Engineering

With the rapid development of polymer solar cells (PSCs), the manufacture of high-performance large area PSC modules is becoming a critical issue in commercial applications. However, most of the reported light absorption materials and interfacial materials are quite thickness sensitive, with optimal thicknesses of around 100 and 5 nm, respectively. The thickness need to be precisely controlled, otherwise, a small variation in thickness can often lead to a sharp decrease in device performance, especially for interfacial materials. This increases the difficulty of apply these materials in the production of large area PSCs. To avoid the shortcomings of thickness-sensitive materials and achieve high-performance large area PSC modules, we designed and synthesized a series of high mobility donor materials and cathode interfacial materials. These materials exhibited excellent device performance at their optimal thicknesses and maintained high performance even with large thickness variations, thus providing a solution to the bottleneck problem in manufacturing PSC modules and enhancing the device reproducibility. We also developed a simple and efficient approach for achieving a large area cathode interlayer with controlled film composition, uniformity, and thickness at the nanometer-scale using an electrostatic layer-by-layer self-assembly (eLbL) process. The eLbL films exhibited excellent cathode modification ability and can be integrated into the current large area device processing techniques. Thus, our approaches from both material design to device engineering provide new solutions for preparing high-performance large area PSC modules.

Dioctylfluorene-thiophene based conjugated copolymers for bulk heterojunction solar cells and enhanced power conversion efficiency via methanol treatment

Sensible design and synthesis of conjugating polymers is important to the development of polymer solar cells (PSCs). In this work, we synthesized and characterized two dioctylfluorene-thiophene based conjugated copolymers, PFTDPP and PFTpBT, having different acceptor groups on the backbone. The photovoltaic properties of the copolymers blended with 6,6-phenyl-C61-butyric acid methyl ester (PC61BM) as an electron acceptor were obtained. The PSC based on a conventional device configuration ITO/PEDOT:PSS/ Polymer:PC61BM/LiF/Al showed power conversion efficiencies (PCEs) of 2.42% and 3.02% for PFTDPP and PFTpBT, respectively. Methanol treatment was introduced to further optimize device performance, and the solvent treatment gave a dramatic increase in PCE. The best PCEs could reach 4.25% and 4.20% after methanol treatment under AM 1.5G illumination with an intensity of 100 mW cm−2 from a solar simulator. © 2015 Society of Chemical Industry

Significant Enhancement of Polymer Solar Cell Performance via Side-Chain Engineering and Simple Solvent Treatment

Rational design and synthesis of polymeric semiconductors is critical to the development of polymer solar cells (PSCs). In this work, a new series of benzodithiophene–difuranylbenzooxadiazole-based donor–acceptor co-polymers—namely, PBDT-DFBO, PBDTT-DFBO, and PBDTF-DFBO, with various side groups—have been developed for bulk-heterojunction PSCs. These side-group substituents provide the opportunity to tailor the opto-electrical properties of the polymers. In addition, we show that the reduction of the bandgap of polymers and the enhancement of charge mobility in the devices can be accomplished concurrently by substituting the alkylthienyl side group with its furan counterpart. In the preliminary investigation, one could obtain PSCs with a power conversion efficiency (PCE) of 2.1% for PBDT-DFBO with an alkoxyl side chain, 2.2% for PBDTT-DFBO with an alkylthienyl side group, and 3.0% for PBDTF-DFBO with an alkylfuranyl side group. Further optimizing the performance of the devices was conducted via a simple s...

Polymer solar cells

This Review summarizes recent progress in the development of polymer solar cells. It covers the scientific origins and basic properties of polymer solar cell technology, material requirements and device operation mechanisms, while also providing a synopsis of major achievements in the field over the past few years. Potential future developments and the applications of this technology are also briefly discussed.