| 초록 |
Two dimensional (2D) materials such as MoS2, WS2, TaS2 (MeS2), and graphene oxide (GO) nanosheets were obtained through the ultra-sonication method and applied to organic photovoltaic cells (OPV) as hole extraction layer (HELs). The work functions (WF) of MeS2 were modified using UV/Ozone (UVO) treatment while the WF of graphene was modulated through the silane-functionalization (SF). The WF of pristine 2D materials are relatively low (WFMoS2 = 4.6 eV, WFWS2 = 4.9 eV, WFTaS2 = 4.4 eV, WFGO = 4.8 eV) comparing with the energy level of active layer. So, the power conversion efficiencies (PCE) of OPVs with MoS2, WS2, TaS2 and GO as HELs are low as 1.08, 1.84, 0.01, and 2.06 %, respectively. After UVO treatment on MeS2 and SF treatment on GO, the WF increased up to approximately 5 eV. The WF increment of MeS2 and GO leads to the significant increase of PCE (2.44, 2.4, 3.06, 3.0 % for UVO-MoS2, UVO-WS2, UVO-TaS2 and SF-GO) through decreasing the energy level difference. |
