Performance Improvement Of Rubrene/C₆₀ Solar Cells

In this thesis, organic solar cells (OSCs) with Rubrene/C6o as an active layer were prepared by thermal evaporation. Three aspects as follows were studied:1. The organic solar cells with a structure of ITO/Rubrene(35 nm)/C6o(35 nm)/BCP(6 nm)/Al(150 nm) were fabricated. The influence of anode modifying layer (MoO3) and 3V bias voltage treatment on device performance were investigated. The experiment results showed that, with inserting the anode modifying layer, the open-circuit voltage and the power conversion efficiency almost increased by a factor of 5.3 and 11.3, respectively. The anode modifying layer can effectively enhance the built-in electric field and assist dissociation and transport excitons. The bias voltage treatment can improve the performance of defective devices by burning partial defects.2. Inverted heterojunction organic solar cells with a structure of ITO/BCP or Alq3(x=0,2,6,10,20,40 nm)/C60 (50 nm)/Rubrene(50 nm)/MoO3(5 nm)/Al(130 nm) were prepared, in which BCP or Alq3 was used as an electron transport layer. The experiment results showed that when BCP or Alq3≤6 nm, device performance hardly changes with the increase of thickness of electron transport layers. When BCP or Alq3≥10 nm, device performance degrades quickly with the increase of thickness of Alq3, while device performance degrades slower and open circuit voltage remains unchanged with the increase of thickness of BCP. When electron transport layer is thin, the rough ITO makes electrons easily injected from C60 into ITO; when electron transport layer is thick, since band bending of BCP/C60 almost make that potential barrier between BCP and C60 does not exist, the bad device performance with BCP mainly comes from poor BCP electron mobility, whereas the bad device with Alq3 was primarily dues to potential barrier between Alq3/C6o.3. The conventional and inverted heterojunction organic solar cells with MoO3 as an anode modification layer and Rubrene/C6o as an active layer were prepared. The inverted devices have better device performance compared with the conventional ones, the open circuit voltage (Voc), short circuit current (Isc), fill factor (FF) and power conversion efficiency (η) increased 34%,20%,25%,102%, respectively.Inserting BCP cathode buffer layer which prevents C60 from the damage by hot Al atoms deposition does not affect the performances of the inverted devices, but remarkably improves those of conventional ones. The influence of MoO3 and BCP on the device performance is analyzed.