Design And Research On Small Molecular Weight Organic Photovoltaic Devices

Organic photovoltaic （OPV） devices have gained considerable attention recentlydue to their potential as low-cost and flexible renewable energy conversion devices.In this thesis, we study the structure and physical mechanism of small molecularweight organic photovoltaic devices for improving their efficiency and lifetime.Enhanced performance of small molecular weight organic solar cells based onCuPc/C₆₀and TiOPc/C₆₀with Ag nanoparticles fabricated on the ITO anode andMoO₃as the anode buffer layer has been demonstrated. Surface plasmon induced bythe incorporation of Ag nanoparticles results in the increased absorption efficiencyand photogenerated exciton dissociation probability of the photoactive layers.Meanwhile, the quenching of the photogenerated excitons at the organic/metalinterface can be successfully restricted by the MoO₃anode buffer layer.Consequently, the short-circuit current is improved while the other parametersmaintain unaffected, which leads to enhanced power conversion efficiency of thedevices.We demonstrate that the improvement of both efficiency and lifetime of organicphotovoltaic devices by employing thin Bphen and thick SnCl₂Pc as the compoundexciton blocking layer （EBL）, where Bphen and SnCl₂Pc acts as the photogeneratedexciton blocking layer and optical spacer, respectively. A thicker SnCl₂Pc layer canbe adopted due to its high electron mobility and aligned lowest unoccupied molecular orbital with the acceptor. The OPV device with such a compound EBLleads to an increase by27%in power conversion efficiency compared to the devicewith a traditional bathocuproine EBL. Moreover, the lifetime is also improved due tothe superior oxygen and moisture diffusion blocking effect of the thick SnCl₂Pclayer.