Research On Novel Material For Polymer Solar Cell And Inverted Configuration Cells

In1986, C.W. Tang firstly named the double layer organic solar cells(OSCs), and Heeger put forward the concept of bulk heterojunction organic solar cells in1995, the OSCs have developed very fast since then. In2012, the power conversion efficiency(PCE) of OSCs have reached10%and maybe commercialized in the near future, while the PCE and stability of OSCs must be improved in the following two research issues for its commercial use. i) The synthetize of new low band-gap polymer donor material is an effective to improve the PCE; ii) Inverted configuration organic solar cells avoid the damage of PEDOT:PSS to ITO and low work function metal is easily oxidized, greatly improve the stability of OSCs. In this paper, we discussed the luminescent and photovoltaic of F8T2; based on the stucture of ITO/Cs2CO3/P3HT:PCBM/MoO3/Al we analysis different annealing treatment on the performance of OSCs. The experimental results indicate i) F8T2is a good donor material and obtained large Voc because of its low highest occupied moleuclar orbits (HOMO) energy lavel; ii) the twice annealing treatment on the P3HT:PCBM and MoO3can effective improve the performance of inverted devices.The luminescent and photovoltaic properties of poly(9,9-dioctylfluorene-co-bithiophene)(F8T2) were studied based on ITO/PEDOT:PSS/F8T2/Bphen/LiF(0or1nm)/Al and ITO/PEDOT:PSS/F8T2:PCBM/Bphen/Al, respectively. The stable and bright yellow emission was obtained from polymer F8T2, the electroluminescence power arrived to45μW at15V driving voltage. Polymer F8T2shows a broad absorption band from400nm to500run, and has a shorter absorption edge about560nm compared with the typical electron donor P3HT (650nm). The photoluminescence quenching of F8T2occurs with only a small fraction of PCBM blended, demonstrating effective photo-induced charge transfer between F8T2and PCBM. The polymer solar cells (PSCs) based on F8T2:PCBM as the active layer show a low power conversion efficiency (PCE) of0.10%with0.91V of open circuit voltage (Voc) and0.23mA/cm2of short circuit current density (Jsc). The PSCs based on F8T2:P3HT:PCBM as the active layer have0.85V of Voc and3.02mA/cm2of Jsc, then resulting in the improvement of PCE about0.90%. The improvement of cells performance should be attributed to the more photon harvested by the introduction of P3HT.Inverted polymer solar cells (IPSCs) use CS2CO3modified ITO as the electrode and MoO3modified Al as the anode was fabricated. The snowflake-like morphology of CS2CO3dissolved in2-ethoxyethanol spin-coated on ITO substrate was characterized by the scanning electron microscope (SEM). Different annealing treatment steps on the IPSCs were carried out to improve the IPSCs performance. The active layers with and without annealing treatment were characterized by absorption spectra, photoluminescence, and morphology to elucidate the effect of annealing treatment on the IPSCs performance. The IPSCs with twice annealing treatments on the active layer and MoO3layers obtained the maximum PCE approaching to2%, with Voc of0.57V, Jsc of8.8mA/cm2and FF of38.7%. However, the performance of IPSC was dramatically decreased by annealing treatment after the deposition of Al cathode, which is still better than the IPSCs without any annealing treatment.