Study On Double Cathode Interface Modification And Active Layer Doping Of Organic Solar Cells

In the past two decades,the traditional silicon solar cells have been the mainstream of the photovoltaic market.With the development of science and technology,the organic solar cells with the advantages of low cost,wide material sources,simple and flexible preparation process have drawn wide attention in the industry.Moreover,how to improve the efficiency of organic solar cells has become the top priority in research.The common method to improve efficiency include designing and synthesizing new narrow bandgap light-absorbing materials,introduction of interface modifier,controlling the morphology of active layer,developing new annealing processes,preparing new electrode materials and doping,and so on..In this paper,the power conversion efficiency of the device is improved by introducing interfacial layer and doping in the active layer,both of which play an important role in improving the efficiency of the organic solar cells.The interface modification layer has the function of regulating the work function of the electrode,reducing the interface barrier and contact resistance between the electrode and the active layer,improving the interface stability between active layer and electrode,and so on.The doping of the active layer can improve the absorption capacity of the photoactive layer,promote the separation of exciton and reduce the carrier recombination.This paper mainly carried out the following two aspects of the work.?1?Alq₃/CaF₂ bilayer structure has been introduced into the organic solar cell as the double cathode interface modifier layer,and the device structure is ITO/PTFE/PCDTBT:PC₇₁BM/Alq₃/CaF₂/Al.Firstly,we fabricated the device with different thickness of CaF₂ and explored the role of CaF₂.It is found that the introduction of CaF₂ reduces the series resistance of the device,resulting in good interface contact between the active layer and the electrode.The power conversion efficiency of the device can reach 6.23%.Next,the device with Alq₃/CaF₂ as a double cathode interface modified layer was prepared.The efficiency is further improved and the maximum power conversion efficiency reaches 7.48%.In devices of this structure,Alq₃ is an organic small molecule material that can be used as an electron extraction layer.The work function of the double cathode interface modified layer structure is more matched with the LUMO level of PC₇₁BM.This structure reduces the surface roughness of the interface compared with the single cathode interface modified layer and improves the transmission and extraction ability of electrons.?2?Carbon/indium oxide composite nanoparticles?C-In₂O₃ NPs?were synthesized by the hydrothermal method.Different concentrations of C-In₂O₃ NPs were doped into the active layer,and the organic solar cells based on the C-In₂O₃NPs active layer were prepared.The structure of the device is ITO/PEDOT:PSS/PCDTBT:PC₇₁BM:C-In₂O₃ NPs/CaF₂/Al.When the active layer is doped with pure In₂O₃ NPs,the power conversion efficiency of the device reaches 5.92%.When the active layer is doped with a composite nanoparticle with a concentration of 1.2wt%,the performance of the device has been improved,and the power conversion efficiency of the device reaches a maximum of 6.82%.This is because the doping of composite nanoparticles enhances the absorption of photons in the active layer,and promotes the charge transfer of active layer,inhibits carrier recombination and reduces the series resistance of the devices.