Jun-hua Wan

Name:

Organization: Hangzhou Normal University

Department: Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education

Title:

Chemicals
References

Donor–Acceptor Conjugated Macrocycles: Synthesis and Host–Guest Coassembly with Fullerene toward Photovoltaic Application

Co-reporter:Si-Qi Zhang, Zhen-Yu Liu, Wei-Fei Fu, Feng Liu, Chuan-Ming Wang, Chun-Qi Sheng, Yi-Fei Wang, Ke Deng, Qing-Dao Zeng, Li-Jin Shu, Jun-Hua Wan, Hong-Zheng Chen, and Thomas P. Russell

ACS Nano November 28, 2017 Volume 11(Issue 11) pp:11701-11701

Publication Date(Web):November 1, 2017

DOI:10.1021/acsnano.7b06961

Electron-rich (donor) and electron-deficient (acceptor) units to construct donor–acceptor (D–A) conjugated macrocycles were investigated to elucidate their interactions with electron-deficient fullerene. Triphenylamine and 4,7-bisthienyl-2,1,3-benzothiadiazole were alternately linked through acetylene, as the donor and acceptor units, respectively, for pentagonal 3B2A and hexagonal 4B2A macrocycles. As detected by scanning tunneling microscopy, both D–A macrocycles were found to form an interesting concentration-controlled nanoporous monolayer on highly oriented pyrolytic graphite, which could effectively capture fullerene. Significantly, the fullerene filling was cavity-size-dependent with only one C70 or PC71BM molecule accommodated by 3B2A, while two were accommodated by 4B2A. Density functional theory calculations were also utilized to gain insight into the host–guest systems and indicted that the S···π contact is responsible for stabilizing these host–guest systems. Owing to the ellipsoidal shape of C70, C70 molecules are standing or lying in molecular cavities depending on the energy optimization. For the 3B2A/PC71BM blended film, PC71BM was intercalated into the cavity formed by the macrocycle 3B2A and provided excellent power conversion efficiency despite the broad band gap (2.1 eV) of 3B2A. This study of D–A macrocycles incorporating fullerene provides insights into the interaction mechanism and electronic structure in the host–guest complexes. More importantly, this is a representative example using D–A macrocycles as a donor to match with the spherical fullerene acceptor for photovoltaic applications, which offer a good approach to achieve molecular scale p–n junctions for substantially enhanced efficiencies of organic solar cells through replacing linear polymer donors by cyclic conjugated oligomers.Keywords: 2D self-assembly; donor−acceptor; fullerene; host−guest; macrocycles; solar cells;

Spiro Linkage as an Alternative Strategy for Promising Nonfullerene Acceptors in Organic Solar Cells

Co-reporter:Xiao-Feng Wu;Wei-Fei Fu;Zheng Xu;Minmin Shi;Feng Liu;Hong-Zheng Chen;Thomas P. Russell

Advanced Functional Materials 2015 Volume 25( Issue 37) pp:5954-5966

Publication Date(Web):

DOI:10.1002/adfm.201502413

This work focuses on developing diketopyrrolopyrrole (DPP)-based small molecular nonfullerene acceptors for bulk heterojunction (BHJ) organic solar cells. The materials, SF-DPPs, have an X-shaped geometry arising from four DPP units attached to a spirobifluorene (SF) center. The spiro-dimer of DPP-fluorene-DPP is highly twisted, which suppresses strong intermolecular aggregation. Branched 2-ethylhexyl (EH), linear n-octyl (C8), and n-dodecyl (C12) alkyl sides are chosen as substituents to functionalize the N,N-positions of the DPP moiety to tune molecular interactions. SF-DPPEH, the best candidate in SF-DPPs family, when blended with poly(3-hexylthiophene) (P3HT) showed a moderate crystallinity and gives a J_sc of 6.96 mA cm⁻², V_oc of 1.10 V, a fill factor of 47.5%, and a power conversion efficiency of 3.63%. However, SF-DPPC8 and SF-DPPC12 exhibit lower crystallinity in their BHJ blends, which is responsible for their reduced J_sc. Coupling DPP units with SF using an acetylene bridge yields SF-A-DPP molecules. Such a small modification leads to drastically different morphological features and far inferior device performance. These observations demonstrate a solid structure–property relationship by topology control and material design. This work offers a new molecular design approach to develop efficient small molecule nonfullerene acceptors.

Evaluation of Heterocycle-Modified Pentathiophene-Based Molecular Donor Materials for Solar Cells

Co-reporter:Qing-Cai Yu, Wei-Fei Fu, Jun-Hua Wan, Xiao-Feng Wu, Min-Min Shi, and Hong-Zheng Chen

ACS Applied Materials & Interfaces 2014 Volume 6(Issue 8) pp:5798

Publication Date(Web):April 1, 2014

DOI:10.1021/am5006223

Two novel solution-processable acceptor–donor–acceptor (A–D–A)-structured organic small molecules with diketopyrrolopyrrole (DPP) as terminal acceptor units and pentathiophene (PTA) or pyrrole-modified pentathiophene (NPTA) as the central donor unit, namely, DPP2(PTA) and DPP2(NPTA), were designed and synthesized. We examined the effects of changing the central bridging heteroatoms of the five-ring-fused thienoacene core identity from sulfur [DPP2(PTA)] to nitrogen [DPP2(NPTA)] in the small-molecule donor material. Replacement of the bridging atom with a different electronic structure has a visible effect on both the optical and electrical properties: DPP2(NPTA), which contains much more electron-rich pyrrole in the central thienoacene unit, possesses red-shifted absorption and a higher HOMO level relative to DPP2(PTA) with the less electron-rich thiophene in the same position. More importantly, substitution of the bridging atoms results in a change of the substituting alkyl chains due to the nature of the heteroatoms, which significantly tailored the crystallization behavior and the ability to form an interpenetrating network in thin-film blends with an electron acceptor. Compared to DPP2(PTA) with no alkyl chain substituting on the central sulfur atom of the PTA unit, DPP2(NPTA) exhibits improved crystallinity and better miscibility with PC71BM probably because of a dodecyl chain on the central nitrogen atom of the NPTA unit. These features endow the DPP2(NPTA)/PC71BM blend film higher hole mobility and better donor/acceptor interpenetrating network morphology. Optimized photovoltaic device fabrication based on DPP2(NPTA)/PC71BM (1.5:1, w/w) has resulted in an average power conversion efficiency (PCE) as high as 3.69% (the maximum PCE was 3.83%). This study demonstrates that subtle changes and tailoring of the molecular structure, such as simply changing the bridging heteroatom in the thienoacene unit in D/A-type small molecules, can strongly affect the physical properties that govern their photovoltaic performances.Keywords: cycle extension; diketopyrrolopyrrole; heterocycle-modified pentathiophene; organic solar cell; solution-processable small molecule; structure−property relationship;

Triphenylamine modified bis-diketopyrrolopyrrole molecular donor materials with extended conjugation for bulk heterojunction solar cells

Co-reporter:Hai-Fen Feng, Wei-Fei Fu, Liangjie Li, Qing-Cai Yu, Hua Lu, Jun-Hua Wan, Min-Min Shi, Hong-Zheng Chen, Zhan’ao Tan, Yongfang Li

Organic Electronics 2014 Volume 15(Issue 10) pp:2575-2586

Publication Date(Web):October 2014

DOI:10.1016/j.orgel.2014.07.020

•Two new triphenylamine (TPA) modified bis-diketopyrrolopyrrole molecular donor materials were synthesized.•Introducing TPA as end-capping donor units induce a significant red-shift (60 nm) of absorption onset.•Unlike most of TPA based molecules, strong aggregation was found in the solid state for both molecules.•A relatively high power conversion efficiency of 4.04% was achieved.Two new solution-processable enlarged π-conjugated donor–acceptor (D–A) organic small molecules consisting of dialkoxysubstituted benzo[1,2-b:4,5-b′]dithiophene (BDT) or dioctyltertthiophene (3T) as the central donor units, diketopyrrolopyrrole (DPP) as the acceptor unit and triphenylamine (TPA) as the terminal conjugated segment, TPA–DPP–BDT and TPA–DPP–3T, were designed and synthesized. Both small molecules possess broad absorption ranging from 300 to 800 nm with an optical band at approximately 1.50 eV and relatively low HOMO energy levels from −5.12 to approximately −5.16 eV. Expectedly, the UV–Vis absorption onset (810 nm) of TPA–DPP–BDT is largely red-shifted (60 nm) relative to that (750 nm) of previously reported BDT(TDPP)2, which consists of BDT and DPP units. Unlike most of the TPA based molecules, strong molecular aggregation was observed in the solid state for both small molecules. In addition, atomic force microscopy (AFM) and X-ray diffraction (XRD) investigations indicated that TPA–DPP–3T and TPA–DPP–BDT exhibit good miscibility with fullerene derivatives. The organic solar cells based on TPA–DPP–BDT/PC61BM(1:1) demonstrated power conversion efficiencies as high as 4.04% with a short-circuit current density (Jsc) of 11.40 mA cm−2 and a fill factor (FF) of 53.2% when the active layer of the cell was annealed at 130 °C for 10 min.Graphical abstract

An Efficient Tin-Free Route to Small Molecules Based on Silole-Modified Pentathiophenes for Solution-Processed Organic Solar Cells

Co-reporter:Qing-Cai Yu;Wei-Fei Fu;Dr. Hong-Yu Wang;Xiao-Feng Wu;Dr. Jun-Hua Wan; Min-Min Shi; Hong-Zheng Chen

Asian Journal of Organic Chemistry 2014 Volume 3( Issue 9) pp:984-993

Publication Date(Web):

DOI:10.1002/ajoc.201402106

Abstract

A acceptor–donor–acceptor (A–D–A) molecule based on a silole-modified pentathiophene (SiPTA) electron-donor unit and two diketopyrrolopyrrole (DPP) acceptor units, DPP₂(SiPTA), was designed and synthesized. An unsymmetrical molecule with D–A structure, DPP-SiPTA, was also synthesized for comparison. Both molecules were synthesized using an environmentally friendly Suzuki coupling protocol, which was modified to avoid ring-opening of the silole under basic conditions. The D–A design has an obvious effect on the electronic structure of these compounds. The D–A–D-structured DPP₂(SiPTA) has a much lower band gap and HOMO than D–A-structured DPP-SiPTA. Furthermore, the molecular symmetry significantly influenced crystallinity. Organic solar cells (OSCs) based on DPP₂(SiPTA)/PC₇₁BM (1:5, w/w; PC₇₁BM=[6,6]-phenyl C₇₁-butyric acid methyl ester) have a power conversion efficiency of 2.36 % with an open-circuit voltage of up to 0.84 V, which, as expected, is much higher than that of the recently reported OSCs based on DPP₂(NPTA) (0.71 V), in which pyrrole-modified pentathiophene (NPTA) is the donor unit.

Phosphole modified pentathienoacene: Synthesis, electronic properties and self-assembly

Co-reporter:Jun-Hua Wan, Wei-Fen Fang, Yi-Bao Li, Xu-Qiong Xiao, Li-Hong Zhang, Zheng Xu, Jia-Jian Peng and Guo-Qiao Lai

Organic & Biomolecular Chemistry 2012 vol. 10(Issue 7) pp:1459-1466

Publication Date(Web):22 Nov 2011

DOI:10.1039/C1OB06584J

A series of new ladder π-conjugated materials, phosphole modified pentathienoacene (PO-PTA), are synthesized and characterized. Single-crystal X-ray results demonstrate that methyl-disubstituted PO-PTA forms a face-to-face dimer structure driven by π–π interactions. The investigations of optical properties showed that the oxidized phosphole moiety in this ladder system can effectively narrow the band gap. PO-PTA is a promising building block in π-conjugated polymers and oligomers for optoelectronic applications. The derivative of PO-PTA, obtained by introducing four long alkyl chains, can self-assemble into one-dimensional (1D) fibers based on intermolecular π–π interactions, dipole–dipole interactions and van der Waals interactions. Interestingly, the uniform and well-ordered monolayers were also obtained for PO-PTA derivative on a HOPG (highly oriented pyrolytic graphite) surface.

2,3,4,5-Tetraphenylsilole-Based Conjugated Polymers: Synthesis, Optical Properties, and as Sensors for Explosive Compounds

Co-reporter:Li-Hong Zhang;Tao Jiang;Dr. Lian-Bin Wu;Dr. Jun-Hua Wan;Dr. Chih-Hsien Chen;Dr. Yong-Bing Pei;Dr. Hua Lu;Yuan Deng;Gao-Feng Bian; Hua-Yu Qiu; Guo-Qiao Lai

Chemistry – An Asian Journal 2012 Volume 7( Issue 7) pp:1583-1593

Publication Date(Web):

DOI:10.1002/asia.201200070

Abstract

A series of linear 2,5-tetraphenylsilole-vinylene-type polymers were successfully synthesized for the first time. The tetraphenylsilole moieties were linked at their 2,5-positions through a vinylene bridge with p-dialkoxybenzenes to obtain polymer PSVB and with 3,6-carbazole to obtain polymer PSVC. For comparison, 2,5-tetraphenylsilole-ethyne-type polymer PSEB was also synthesized, in which the vinylene bridge of PSVB was replaced with an ethyne bridge. Very interestingly, the bridging group (vinylene or ethyne) had a significant effect on the photophysical properties of the corresponding polymers. The fluorescence peak of PSEB at 504 nm in solution originated from the emission of its silole moieties, whereas PSVB and PSVC emitted yellow light and no blueish–green emission from the silole moieties was observed, thus demonstrating that the emissions of PSVB and PSVC were due to their polymer backbones. More importantly, the 2,5-tetraphenylsilole-ethyne polymer exhibited a pronounced aggregation-enhanced emission (AEE) effect but the 2,5-tetraphenylsilole-vinylene polymer was AEE-inactive. Moreover, both AEE-active 2,5-tetraphenylsilole-ethyne polymer and AEE-inactive 2,5-tetraphenylsilole-vinylene polymers were successfully applied as fluorescent chemosensors for the detection of explosive compounds.