Study On The Performances Of Polymer Solar Cell By Annealing And Magnetic Field Treatment

With the green development concept deeply rooted,the new energy technologieshave developed rapidly,especially in solar cell technology.Different from traditionalsilicon-based solar cell,organic solar cell possesses lots of excellent features such asrich source of raw materials, simple preparation process and easy manufacture oflarge scale,which there is no doubt that is the direction of futuredevelopment.Recently organic solar cell energy conversion efficiency(PCE) hasreached up to7%,but still a big space to ascension and many problems need to bestudied:research and development of new functional materials,device structureoptimization and preparation process improvement. Therefore this paper focus onraising the PCE of polymer solar cell by annealing and magnetic treatmenttechnology.We obtained good results and analyzed its causes.1.We research polymer solar cell based on donor P3HT and acceptor PCBM witha device structure of ITO/PEDOT:PSS/P3HT:PCBM/Al.By changing the annealingmethod,We find that post-annealing treatment is more effective than pre-annealingtreatment obviously,due to Al electrode limit movement of polymer long chain in thevertical direction,making the polymer chain more orderly arranged in the horizontaldirection.Open circuit voltage and short circuit current density is significantlyimproved,the PCE is0.3%.Through the regulation of the annealing time,30min isproper for fabricating the best performance device.Finally we use three differentorganic solvents(chlorobenzene,dichlorobenzene,chloroform) to prepare the activelayer respectively.The results show that the performance of device by usingchlorobenzene as solvent is the best among three,the PCE of0.3%is achieved,shortcircuit current density of3.34mA/cm2,open circuit voltage of0.326V. The reason isthat long condensing time of films is helpful for improving carrier mobility.2.We research polymer solar cell based on donor P3HT and acceptor PCBM witha device structure of ITO/PEDOT:PSS/P3HT:PCBM/Al.We find that short circuitcurrent density enhance a lot,a growth of about24%by using magnetic fieldtreatment,and during the first2hours of magnetic field treatment the short circuitcurrent density increases with the time passing.A reason which can explain thisphenomenon is that Zeeman splitting by magnetic field effect reduce the intersystemcrossing from singlet polaron pairs to triplet polaron pairs.It make the singlet polaronpairs increase and effectively change the relative ratio between the singlet and triplet polaron pairs,strengthening the exciton separation ability and resulting in more freecarriers.3.We research that annealing treatment and magnetic field treatmentcomprehensively effect on the performance of device based on the structure ofITO/PEDOT:PSS/P3HT:PCBM/Al.It is found that the way of first magnetic fieldtreatment second annealing treatment is better for the optimization of device than theorder is inverted.When we have a first60min magnetic field treatment under250mTmagnetic field intensity and a second30min annealing treatment under120℃temperature，we can obtain the best performance device that short circuit currentdensity,open circuit voltage,fill factor and PCE reach4.31mA/cm2、0.392V、25%and0.4%respectively.