Huiyang Li

Novel pyrrole-based dyes for dye-sensitized solar cells: From rod-shape to “H” type

A series of “H” type dye sensitizers with pyrrole as the conjugated bridge were synthesized, in which two pieces of N-arylpyrrole-based organic dye moieties were linked together through various aromatic rings. Interestingly, the introduced aromatic isolation group not only gave a new possibility to modify the construction structure, but also controlled the topological structure of the resultant dyes in some degree. As a result, their performance could be adjusted, and the configuration of “H”-type could suppress the aggregations on the TiO2 surface. The performance of the DSCs based on these dyes as the sensitizers demonstrated that the structure of these dyes was beneficial to the devices, and the conversion efficiency of the solar cell based on dye LI-22 with carbazole as the isolation group was as high as 5.22%.

The introduction of conjugated isolation groups into the common acceptor cyanoacrylic acid: an efficient strategy to suppress the charge recombination in dye sensitized solar cells and the dramatically improved efficiency from 5.89% to 9.44%

The traditional acceptor, cyanoacrylic acid, was modified by the insertion of different aromatic rings as the isolation groups between the CN and COOH moieties, with the aim to suppress the possible charge recombination in dye sensitized solar cells. The results indicated that the larger isolation group was beneficial to inhibit the interfacial recombination, and the highest Voc was obtained by dye LI-78 with biphenyl as the isolation group. Combined with electron injection, the highest conversion efficiency (η) of 9.44% was achieved by dye LI-76 featuring a phenyl unit as the isolation group, whereas that of the reference sensitizer LI-75 without isolation group was only 5.89% under the same test conditions, providing a simple and convenient method to optimize the photovoltaic performance of organic dyes.

Reaction-based conjugated polymer fluorescent probe for mercury(II): good sensing performance with “turn-on” signal output

Based on a Hg2+-promoted deprotection reaction of dithioacetal, the conjugated polymer PDT was designed. PDT exhibited significant fluorescence enhancement along with an apparent red-shift upon the addition of mercury ions. Due to the specific chemical reaction, the response was very fast with good selectivity towards Hg2+. Other metal ions, including K+, Na+, Li+, Ba2+, Mg2+, Pb2+, Ca2+, Mn2+, Fe2+, Co2+, Fe3+, Cu2+, Ni2+, Al3+, Cd2+, Cr3+, and Zn2+, had nearly no influence on the sensing process. Moreover, PDT showed high sensitivity with the detection limit of 1.0 × 10−6 mol L−1 and 1 × 10−5 mol L−1 in solution and as test strips, respectively, as a result of the molecular wire and signal amplification effects.

Co-sensitization of “H”-type dyes with planar squaraine dyes for efficient dye-sensitized solar cells

Three “H”-type dyes with different linkage mode of two “D–π–A” moieties (LI-101, LI-102 and LI-103) were synthesized and applied to the co-sensitized system with the famous metal-free NIR squaraine dye of SQ2. Thanks to the advantage of the “H” configuration and their complementary spectra, the co-sensitized system exhibited the much improved photovoltaic performance of about a 70% enhancement, in comparison with that of SQ2 itself. Among them, the LI-102/SQ2 co-sensitized solar cell exhibited the highest conversion efficiency of 7.44% with 16.6 mA cm−2 for Jsc, 714 mV for Voc, 0.63 for FF.

Substituent effect of Ru(II)-based sensitizers bearing a terpyridine anchor and a pyridyl azolate ancillary for dye sensitized solar cells

In this study we explore the substituent effects of a class of Ru(II)-based sensitizers bearing a 4,4′,4′′-tricarboxy-2,2′:6′,2′′-terpyridine anchor, a functional pyridinyl azolate and a single thiocyanate ligand. Three sensitizers, i.e.PRT-tBu, ND-1 and ND-2, with t-butyl, 5-[4-[bis(4-hexyloxyphenyl)amino]phenyl]-2-thienyl and 5-[7-[4-[bis(4-hexyloxyphenyl)amino]phenyl]-4-(2,1,3-benzothiadiazolyl)]-2-thienyl substituents are designed and synthesized. Their photophysical and redox properties are probed using UV/vis absorption and cyclic voltammetry studies. The DSC cell performances (JSC, VOC and PCE) were also examined and analyzed in order to elucidate the structure–property relationships. It is notable that all sensitizers showed superior spectral responses in the region up to 830 nm, among which the PRT-tBu and ND-1 showed prolonged electron lifetimes, suppressed electron recombination and higher power conversion efficiencies (PCE) compared to the third sensitizer PRT-ND2 with a benzothiadiazolyl linker at the ancillary chelate. In particular, the optimized DSC device using the PRT-tBu sensitizer gives a JSC of 16.29 mA cm−2, a VOC of 787 mV and a fill factor (FF) of 0.75, corresponding to an overall PCE of 9.68% under standard global AM 1.5 solar irradiation. Its adequate performance plus simplified synthetic procedures warrant its application in larger sized DSCs.

New anthracene-based organic dyes: the flexible position of the anthracene moiety bearing isolation groups in the conjugated bridge and the adjustable cell performance

Three organic sensitizers (LI-65–LI-67), featuring a 9,10-diarylsubstituted anthracene unit as part of the conjugated bridge, were designed and employed in dye-sensitized solar cells (DSCs). The two phenyl groups on the 9 and 10 positions of the anthracene ring acted as isolation groups, to suppress possible dye aggregation and electron recombination. With the flexible position of the isolation group in the conjugated bridge, interesting structure–property relationships were obtained: the isolation groups (the phenyl rings on the anthracene unit), close to the donor, were beneficial to the enhancement of the short circuit current (Jsc) values, with the highest Jsc value of 13.95 mA cm−2 (LI-65); once located in the middle of the π-bridge, the highest resistance of charge recombination and the longest electron lifetime were achieved and contributed to the enhanced open circuit voltage (Voc) of 722 mV, with the highest conversion efficiency (η) of 6.44% (LI-66, 25% higher than the lowest).

Some new molecular design strategy to improve the performance of organic dyes in dye sensitized solar cells

With the aim to obtain good metal free organic dyes with high performance, different series of dyes were designed by optimizing their structures. Based on the experimental results, the relationship between the structure and property is summarized, to provide some useful information for the further development of new organic dyes.