New triphenylamine-based sensitizers bearing double anchoring units for dye-sensitized solar cells

Two organic sensitizers （LI-33 and LI-34） with double anchoring units were synthesized and utilized for dye sensitized solar cells （DSSCs）, which contained thiophene or vinyl thiophene as n-bridge. The introduction of double anchoring units can change their absorption spectra and energy levels in a large degree, thus, the better light-harvesting ability and the convenient electron transfer along the whole molecule can be obtained. The solar cell based on LI-34 exhibited a broad incident photon- to-current conversion efficiency （IPCE） spectrum and high conversion efficiency （η=6.05%） with coadsorbent CDCA.

Donor design and modification strategies of metal-free sensitizers for highly-efficient n-type dye-sensitized solar cells

Dye-sensitized solar cells （DSSCs） cannot be developed without the research on sensitizers. As the key of light harvesting and electron generation, thousands of sensitizers have been designed for the application in DSSC devices. Among them, organic sensitizers have drawn a lot of attention because of the flexible molecular design, easy synthesis and good photovoltaic performance. Recently, new record photovoltaic conversion efficiencies of 11.5% for DSSCs with iodide electrolyte and 14.3% for DSSCs with cobalt electrolyte and co-sensitization have been achieved with organic sensitizers. Here we focus on the donor design and modification of organic sensitizers. Several useful strategies and corresponding typical examples are presented.

Organic sensitizers with different thiophene units as conjugated bridges:molecular engineering and photovoltaics

Three structural modifications with incorporation of alkyl,alkoxy and vinyl bond into the skeleton of thiophene bridge in D-π-A featured organic sensitizers are specifically developed for insight into their influences on photophysical,electrochemical as well as photovoltaic properties in nanocrystalline TiO_2-based dye sensitized solar cells(DSSCs).The insertion of vinyl bond into the conjugation bridge leads to the molecular planar configuration,and the conjugation bridge of 3,4-ethylenedioxythiophene(EDOT)is prone to positively shift its highest occupied molecular orbital(HOMO).The electrochemical impedance spectroscopy(EIS)results indicate that the grafted long alkyl chain onto thiophene is favorable to suppress dye aggregation when adsorbed onto TiO_2film and modification on interface of TiO_2/dye/electrolyte,resulting in a relatively high open-circuit voltage(V_(oc)).Under optimized conditions,dye LS-4 bearing hexylthiophene as the conjugation bridge shows a relatively high overall conversion efficiency of5.45%,with a photocurrent of 11.61 mA cm^(-2),V_(oc)of 744 mV.