Jhong-Sian Wu

Combination of Molecular, Morphological, and Interfacial Engineering to Achieve Highly Efficient and Stable Plastic Solar Cells

A flexible solar device showing exceptional air and mechanical stability is produced by simultaneously optimizing molecular structure, active layer morphology, and interface characteristics. The PFDCTBT-C8-based devices with inverted architecture exhibited excellent power conversion efficiencies of 7.0% and 6.0% on glass and flexible substrates, respectively.

Influences of the Non-Covalent Interaction Strength on Reaching High Solid-State Order and Device Performance of a Low Bandgap Polymer with Axisymmetrical Structural Units

A high organic field-effect transistor mobility (0.29 cm(2) V(-1) s(-1) ) and bulk-heterojunction polymer solar cell performance (PCE of 6.82%) have been achieved in a low bandgap alternating copolymer consisting of axisymmetrical structural units, 5,6-difluorobenzo-2,1,3-thiadiazole. Introducing the fluorine substituents enhanced intermolecular interaction and improved the solid-state order, which consequently resulted in the highest device performances among the 2,1,3-thiadiazole-quarterthiophene based alternating copolymers.

Donor–acceptor polymers based on multi-fused heptacyclic structures: synthesis, characterization and photovoltaic applications

We report here two novel 2,7-fluorene- and 2,7-carbazole-based conjugated polymers PFDCTBT and PCDCTBT containing ladder-type heptacyclic structures with forced planarity. PCDTBT shows excellent solubility, low band gap and high hole mobility, leading to a power conversion efficiency of 3.7%.

Porphyrin‐Incorporated 2D D–A Polymers with Over 8.5% Polymer Solar Cell Efficiency

A copolymerization strategy is developed to utilize porphyrin as a complementary light-harvesting unit (LHU) in D-A polymers. For polymer solar cells (PSCs), the presence of LHUs increases the short-circuit current density (Jsc ) without sacrificing the open-circuit voltage (Voc ) and fill factor (FF). Up to 8.0% power conversion efficiency (PCE) is delivered by PPor-2:PC71 BM single-junction PSCs. A PCE of 8.6% is achieved when a C-PCBSD cathodic interlayer is introduced.

A pentacyclic nitrogen-bridged thienyl-phenylene-thienyl arene for donor-acceptor copolymers: synthesis, characterization, and applications in field-effect transistors and polymer solar cells.

A pentacyclic benzodipyrrolothiophene (BDPT) unit, in which two outer thiophene rings are covalently fastened with the central phenylene ring by nitrogen bridges, was synthesized. The two pyrrole units embedded in BDPT were constructed by using one-pot palladium-catalyzed amination. The coplanar stannylated Sn-BDPT building block was copolymerized with electron-deficient thieno[3,4-c]pyrrole-4,6-dione (TPD), benzothiadiazole (BT), and dithienyl-diketopyrrolopyrrole (DPP) acceptors by Stille polymerization. The bridging nitrogen atoms make the BDPT motif highly electron-abundant and structurally coplanar, which allows for tailoring the optical and electronic properties of the resultant polymers. Strong photoinduced charge-transfer with significant band-broadening in the solid state and relatively higher oxidation potential are characteristic of the BDPT-based polymers. Poly(benzodipyrrolothiophene-alt-benzothiadiazole) (PBDPTBT) achieved the highest field-effect hole mobility of up to 0.02 cm(2) V(-1) s(-1). The photovoltaic device using the PBDPTBT/PC(71)BM blend (1:3, w/w) exhibited a V(oc) of 0.6 V, a J(sc) of 10.34 mA cm(-2), and a FF of 50%, leading to a decent PCE of 3.08%. Encouragingly, the device incorporating poly(benzodipyrrolothiophene-alt-thienopyrrolodione) (PBDPTTPD)/PC(71)BM (1:3, w/w) composite delivered a highest PCE of 3.72%. The enhanced performance arises from the lower-lying HOMO value of PBDPTTPD to yield a higher V(oc) of 0.72 V.

Interface Engineering to Enhance the Efficiency of Conventional Polymer Solar Cells by Alcohol-/Water-Soluble C60 Materials Doped with Alkali Carbonates

Two new C60-based n-type materials, EGMC-OH and EGMC-COOH, functionalized with hydrophilic triethylene glycol groups (TEGs), have been synthesized and employed in conventional polymer solar cells. With the assistance of the TEG-based surfactant, EGMC-OH and EGMC-COOH can be dissolved in highly polar solvents to implement the polar/nonpolar orthogonal solvent strategy, forming an electron modification layer (EML) without eroding the underlying active layer. Multilayer conventional solar cells on the basis of ITO/PEDOT:PSS/P3HT:PC61BM/EML/Ca/Al configuration with the insertion of the EGMC-OH and EGMC-COOH EML between the active layer and the electrode have thus been successfully realized by cost-effective solution processing techniques. Moreover, the electron conductivity of the EML can be improved by incorporating alkali carbonates into the EGMC-COOH EML. Compared to the pristine device with a PCE of 3.61%, the devices modified by the Li2CO3-doped EGMC-COOH EML achieved a highest PCE of 4.29%. Furthermore, we demonstrated that the formation of the EGMC-COOH EML can be utilized as a general approach in the fabrication of highly efficient multilayer conventional devices. With the incorporation of the EGMC-COOH doped with 40 wt % Li2CO3, the PCDCTBT-C8:PC71BM-based device exhibited a superior PCE of 4.51%, which outperformed the corresponding nonmodified device with a PCE of 3.63%.

Synthesis and morphological studies of a poly(5,6-difluorobenzo-2,1,3-thiadiazole-4,7-diyl-alt-quaterchalcogenophene) copolymer with 7.3% polymer solar cell efficiency

To obtain a poly(5,6-difluorobenzo-2,1,3-thiadiazole-4,7-diyl-alt-quaterchalcogenophene) (P(FBT-alt-CP4)) copolymer with a small optical band gap (Eg), and to achieve high short-circuit current (Jsc) in the P(FBT-alt-CP4) : PC71BM polymer solar cells (PSCs), P(FBT-alt-Se2Th2), which contains selenophene-2,5-diyl (–Se–) π-bridges, was synthesized. P(FBT-alt-Se2Th2) shows a Eg of 1.56 eV and is strongly aggregated in solution. Wide angle X-ray diffraction (WAXD) and grazing incidence X-ray diffraction (GI-XRD) results revealed the high solid-state order of P(FBT-alt-Se2Th2) and its edge-on orientation on the substrate. It delivered a high hole mobility (μh) of 0.36 cm2 V−1 s−1 in organic field-effect transistors (OFETs). The strong aggregation tendency of P(FBT-alt-Se2Th2) caused large segregation domains in the P(FBT-alt-Se2Th2) : PC71BM thin film, as is seen in the high-resolution transmission electron microscopy (HR-TEM) images. The addition of 8 vol% of 1-chloronaphthalene (1-CN) effectively suppressed the aggregation and led to more homogeneous active layer morphology. The improved morphology enhanced the Jsc of the PSCs. A superior PCE of 7.34% with a Voc of 0.70 V, a Jsc of 15.8 mA cm−2, and a FF of 66.4% was achieved in the inverted P(FBT-alt-Se2Th2) : PC71BM PSCs. The strong aggregation of P(FBT-alt-Se2Th2) is likely related to its more straight conjugated backbone according to the theoretical calculation results of the FBT-alt-Se2Th2 repeat unit.

Recent Advances in P-Type Conjugated Polymers for High-Performance Solar Cells

Bulk-heterojunction (BHJ) polymer solar cells have achieved significant progress in the recent years, with the efficiency now over 10 %. The p-type polymer in the BHJ blend played a key role in the amazing technology advance. In this chapter, we will timely update over 80 conjugated polymers leading to high-performance solar cells. The principle of molecular design with structure-properties relationship with respect to device characteristics will also be discussed, as the materials and morphology are tightly interconnected.