Application Of Solvent Additives And Cathode Modification In Polymer Solar Cells

With the growing global energy and environmental problems，The voice of developingnew energy technologies is rising。 And the organic solar cell caused widely attention andfavor of scientific research personnel because of its structure and preparation process issimple，light weight，can be prepared in a large area，flexible and other advantages。However，the low power conversion efficiency of organic solar cells is the major obstacle to realize itslarge-scale industrialized production。Therefore，how to improve the photoelectric conversionefficiency of organic solar cells become the research focus in the field of polymer solar cells。This paper focus on the bulk heterojunction solar cells, mainly researched the2-bromophenolas solvent additives and spincoated Carbamide as the cathode buffer layer on the performanceof polymer solar cells。The main research contents and conclusions are as follows：Firstly， we fabricate solar cells based on poly (3-hexylthiophene)(P3HT) and thederivatives of C60(PCBM) as the active layer material, chlorobenzene (CB) as solvent。Investigated the2-Bromophenol as solvent additives on the performance of polymer solarcells. By comparing five groups of device performance under different additive content,wefound that when2-Bromophenol volume ratio is1.5%， the device performance optimal。Compared with the reference device we found that the uv-visible absorption spectrum showsred shift phenomenon，external quantum efficiency (EQE) curve peak improved significantly，At the same time between the donor and receptor materials form good phase separationstructure。In a100mw/cm2light intensity, the energy conversion efficiency is improved from2.32%to2.90%, which increased about25%。Secondly,We use the method of solution spincoating researched organic small moleculeof urea (Carbamide， UREA) as the cathode buffer layer on performance of polymer solarcells. By changing the rotational speed of the spincoater to obtain cathode buffer layer ofdifferent thickness and observed its effect on the cell performance。We find that With3000rpm got about3nm thick UREA as cathode buffer layer, the performance of device structureof ITO/PEDOT/PSS/P3HT/PCBM/UREA/Al is best,and the energy conversion efficiencyfrom2.80%increased to3.36%,improved20%。By carrying out a series of characterizationsincluding dark J-V curve, Atomic Force Microscopy (AFM), external quantum efficiency(EQE). we proposed that the introduction of urea can form an interfacial dipole layer betweenthe active layer and the Al electrode， which lowered the interfacial potential between theelectron acceptor and the Al electrode, so improved the cathode’s electron collectionefficiency; Meanwhile, the reaction between the lone pair electrons of urea molecule and theAl electrode reduced the amount of Al atoms that diffusing into the active layer,whichproteced the active layer。...