Synthesis And Aqueous-processed Hybrid Solar Cells Application Of Water Soluble PPV Derivatives

In recent years,aqueous-processed polymer/nanocrystal hybrid solar cells(HSCs)have attracted much attention due to the low cost,flexibility,handleability of conjugated polymers and the high charge carrier mobility,stability of inorganic nanocrystals(NCs).Additionally,it can solve organic pollution problem by using water as a clean solvent.In this paper,a series of water soluble poly(phenylenevinylene)(PPV)precursors have been synthesized and adopted in aqueous-processed polymer/nanocrystal HSCs.After changing experiment parameters,the power conversion efficiency(PCE)has been improved.Furthermore,the key factors limiting HSCs performance have been deeply investigated.Particularly,there are three sections in details in the following parts.1.Water-soluble poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene](MEH-PPV)precursor is synthesized through the Wessling polymerization process.After annealing at the proper temperature(220-400 oC),the precursor can be convert to MEH-PPV with conjugated structure,which has been proved by thermal gravity analysis,Fourier-transform infrared and other characterizations.This approach makes polymers and Cd Te NCs build an interpenetrating network structure is constructed.And the positive side-chain groups of the precursor can be easily eliminated.It could effectively prevent the charges of the polymer acting as traps,and provide possibility to fabricate photovoltaic devices.2.MEH-PPV precursor and water soluble Cd Te have been used to fabricate HSCs by being mixed,spin coating,annealing and other operations.We investigate the HSCs performance by changing the mass ratio of polymer:NCs(1:6,1:12,1:18).The results of TEM images and AFM images indicate that 1:12 is the optimized ratio of MEH-PPV:Cd Te.When the weight ratio is 1:12,MEH-PPV percolates through the voids of Cd Te NCs,which are formed as an interpenetrating network structure.This type of bicontinuous percolation network prolongs carrier lifetime.Furthermore,a larger donor/acceptor interface improves the exciton dissociation efficiency.Then,an optimized annealing temperature(315 oC)has been found.A PCE of 4.20% is achieved under simulated 100 m W cm2 AM 1.5G illumination.3.poly[2,5-dimethoxy-1,4-phenylenevinylene](DMe O-PPV)and poly[2,5-dimethyl-1,4-phenylenevinylene](dm-PPV)are synthesized for further promoting the hole extraction ability and carrier mobility of PPV derivatives in HSCs.After comparing these two new polymers with PPV,MEH-PPV and MPPV,we find that DMe O-PPV has strong electron-releasing ability,which can increase the electron cloud density of conjugated backbone.The advantage of this structure endows high HOMO energy level to DMe O-PPV,that it can accept holes efficiently.The carrier mobility of DMe O-PPV and dm-PPV is 5-10 times higher than MEH-PPV.The hybrid layers of DMe O-PPV/Cd Te and dm-PPV/Cd Te exhibit more effective interpenetrating network structure.The HSCs fabricated with DMe O-PPV and Cd Te has achieved a high PCE of more than 5%.In conclusion,a series of PPV derivatives/Cd Te HSCs have been constructed with an environmentally friendly process.Moreover,the HSCs performance has been optimized,and the operation mechanism has been investigated profoundly.Therefore,this work is instructive for designing and fabricating high performance HSCs.