The Molecular Engineering Of Diketopyrrolopyrrole-Based Sensitizer For Solar Cell Application

Dye-sensitized-solar-cells (DSCs), inspired by plant photosynthesis, is a new generation photovoltaic technology, owing to the potential advantages of low cost, easy production and flexibility relative to semiconductor photovoltaic cells. In this device, a monolayer of dye molecules are adsorbed on the surface of nanostructured TiO2as a sensitizer, generate electron-hole pair upon light illumination, and the electron transfers through TiO2while the hole transfers through an electrolyte used. As the sensitizer, dye is one of the key components for harvesting solar light in DSCs.In this paper, a series of organic dyes were prepared with an electron donor-π bridge-electron acceptor (D-π-A) structure, where diketopyrrolopyrrole (DPP) was employed as a bridge. The DPP has a uniquely planar conjugated bicyclic structure with an electron-withdrawing property, and its derivatives are extensively used as high-performance pigments due to the exceptional photochemical and thermal stability. Due to its electron-deficient planar bicyclic conjugation, DPP bridge in the D-π-A dye can effectively extend the dye absorption spectrum, enhance light harvesting ability in the solar spectrum, and improve photocurrent and device power conversion efficiency. Moreover, the DPP unit has multi-active sites, and can be modified with different functional groups to adjust their properties. In these D-π-A dyes, different triarylamine derivatives were employed as electron donor and acrylonitrile as electron acceptor. The main works are listed as follows:1, We utilized2,5-dioctyl-3,6-bis(4-bromophenyl)pyrrolo[3,4-c] pyrrole-1,4-dione as π-conjugated bridge, acrylonitrile as electron acceptor, triarylamine and bis(4-tert-butylphenyl)phenylamine respectively as electron donor, were designed dye--S1and dye-S2.2,We utilized3,6-bis(4-bromophenyl)-2,5-dihexylpyrrolo[3,4-c] pyrrole-1,4(2H,5H)-dione as π-conjugated bridge, acrylonitrile as electron acceptor, bis(4-tertbutylphenyl) phenylamine and4-(hexyloxy)-N-(4-(hexyloxy)-phenyl)-N-phenyl-aniline respectively as electron donor, were designed dye-Rland dye-R2.3,We utilized1,4-Diketo-2,5-di(2-ethylhexyl)-3,6-bis(4-bromophenyl) pyrrolo-[3,4-c]-pyrrole as π-conjugated bridge, acrylonitrile as electron acceptor, bis(4-tert-butylphenyl)phenylamine and4-(hexyloxy)-N-(4-(hexyloxy)-phenyl)-N- phenyl-aniline respectively as electron donor, were designed dye-Lland dye-L2.The DPP-based dyes were characterized for their physicochemical properties, and employed as sensitizers in DSCs. The structure-property relationship of the dyes was studied. All the dyes showed high power conversion efficiency as sensitizers in DSCs, in which L2-based DSC presented the best performance with Jsc16.34mA cm-2, Voc750mV, and fill factor (FF)0.74, corresponding to9.1%of power conversion efficiency under full sun (AM1.5,100mW cm-2).