The Polymer Solar Cells Based On Bulk Heterojunction Of P3HT Codoped With C₆₀ And PCBM

Solar energy has become more and more attractive because it is clean and renewable.The efficiency of solar cells based on inorganic semiconductor can reach 15%,but the biggest obstacle of the crystalline silicon-based photovoltaic device is the high semiconductor manufacturing cost and finally limits it's utility.While polymer-based photovoltaic devices have shown great promising potential because it is mechanical flexible and durable,and the chemical structure can be easily manipulated, in addition,polymer-based photovoltaic devices have a lower fabricate cost.Recently many studies have worked on the solar cells used P3HT(Poly(3-Hexylthiophene)) and PCBM([6,6]-phenyl C61-butyric Acid Methyl Ester),its power conversion efficiency have already broken through 6%.Comparing with inorganic solar cells,organic photovoltaic is limited by the low convert efficiency.Recent researches are concentrating on selecting new materials and structure optimization finally to improve the efficiency.In this thesis,we recall the OPVs' development history at first,and then illustrate some general fabrication and materials which are often used in experiments and analyze the basic theory of OPV.At last C₆₀ was introduced into the devices based on P3HT: PCBM,the influence of C₆₀ in improving the efficiency has been studied finally.The devices with the structures of ITO/PEDOT:PSS/P3HT:PCBM/A1 and ITO/PEDOT:PSS/P3HT:PCBM:C₆₀/A1 were fabricated.And their I-V curves were compared.the reasons of C₆₀ improving the power conversion efficiency are concluded as following:1.The addition of C₆₀ can modify the LUMO of the acceptor(PCBM and C₆₀), which results in the increase in open circuit voltage(Voc).2.The shunt resistance and the open circuit voltage can be enhanced by post-annealing which improve the morphology of P3HT:PCBM active layer.Besides, there is a lower series resistance and a ordered self-organization effect for the polymer film then create a higher short circuit current.Meanwhile,the solar cell based on P3HT: PCBM:C₆₀ has a better morphology though a post-annealing at 140℃for 10 minutes.3.The effect of solvent on the performance of polymer solar cell was found. After introducing C₆₀ into the BHJ,the device based on P3HT:PCBM fabricated in CB solution has a higher efficiency However,it is found that higher fill factor and performance were obtained in the devices from ODCB solution due to a better morphology.4.The device based on P3HT:PCBM:C₆₀ blend has a better ordered morphology than P3HT:PCBM.We find out that after adding C₆₀ into the solution,there is an efficient phase separation in the blend film;C₆₀ will form a path way which connect the metal cathode and finally collect carriers.C₆₀ clusters will play like an highly efficient electron-transfer pathway.