Using Carbon Nanotubes In Organic Solar Cells

As a renewable and clean energy,the solar power generation plays an important role.There are many types of solar cells such as conventional silicon solar cells,GaAs,InP,GaInP,CIGS,CdTe,Perovstike,CZTS,Dye-sensitized,etc.Here the research on organic solar cells was carried out as they are considered as the cheaper solar cells.The organic solar cells are also considered as the replacement of conventional silicon solar cells due to their low cost,mechanical flexibility,simple fabrication and they can also be made in different colors.The efficiency of organic solar cells reaches up to 17%which still is not enough to launch them in market.The carbon nanotubes have excellent mechanical,electrical and optical properties and these nanotubes can be conductors or semi-conductors depending on their chirality.In this research the carbon nanotubes have been incorporated in buffer and active layers of organic solar cells as well as these are also used as electrode of organic solar cells to replace ITO because ITO is the weakest part of organic solar cells while CNTs have good mechanical properties and flexibility,so these nanotubes have also been tried to replace the brittle and weak part of the organic solar cells.100nm MWCNTs are mixed in PEDOT:PSS with different concentrations in P3HT:PCBM organic solar cells and Isc is increased from 8.82 to 9.5(mA/cm2),F.F is improved from 43 to 47.4 and PCE is improved from 2.1%to 2.39%.Similar MWCNTs are incorporated in active layer i.e.P3HT:PCBM photoactive layer with different concentrations(1%to 5%),the short circuit current was improved from 5.93 to 8.53(mA/cm2)but there were not much improvements in PCE due to the problems in separation,dispersion and alignment of these nanotubes.Not much improvement in the performance of solar cell has been seen when the ITO is replaced by SWCNTs,but there was improvement in the transmittance when these nanotubes are mixed with MoO3.There are some problems which should be removed from nanotubes before using them in OSCs such as,entanglement,solubility,and non-alignment which are discussed in detail and different processes have been applied to overcome these barriers,these processes are sonication,acid treatment,nanotubes shearing,etc.Overall from the whole results it has been reported that further research is needed in future to perform the perfect alignment,proper dispersion and separation to improve the efficiency,short circuit current and mechanical strength of the organic solar cells.