Multi-thin layers as electrodes for organic solar cell:Elaboration and numerical modeling

Abstract

In this work, the conventional and inverse organic solar cells (OSC and IOSC) were studied and improved using the GPVDM software. The initial studied two cells (OSC and IOSC) consist a of photoactive layer (PAL), an electron transporting layer (ETL) and a hole transporting layer (HTL). The PAL was a blend of the poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methylester (PCBM) organic semiconductor (P3HT:PCBM). The initial ETL was Tittanium Oxide (TiOx) while the ETL was a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) with a thickness of 50 nm in OSC and IOSC. The effect of the active layer thickness was systematically investigated, then the ETL and HTL thicknesses effect were studied. Also, a group of candidate materials were proposed as ETL and HTL. It was found that the best ETL and HTL were TiOx and Cu2O respectively for the conventional cell while they were PEDOT:PSS and ZnO for the inverse cell. The optimised efficiency for normal and reverse cells were 4.77% and 5.35% for both Al/ TiOx (50 nm)/ P3HT:PCBM (150 nm)/ Cu2O (10 nm)/ITO and Ag/ PEDOT:PSS (20 nm)/ P3HT:PCBM (200 nm)/ ZnO (30nm)/ ITO for normal and reverse cells. Multilayer electrodes of the form TCO / Ag / TCO were also proposed and improved within GPVDM. It was found that AZO (40 nm) / Ag (6 nm) / AZO (40 nm) is the best alternative to ITO with efficiencies improved to 4.96% and 5.29% for the normal and inverse cells respectively. The same study was carried out using the SILVACO ATLAS software. The results showed that the best efficiency for the normal cell reached 4.73% for the structure Al / ZnO (10 nm) /P3HT:PCBM (100 nm) / PEDOT:PSS (10 nm) / ITO OSC, while it reached 4.77% for an Ag/ NiO (10 nm)/ P3HT:PCBM (300 nm)/ TiO2 (60nm)/ITO IOSC. The TCO/Ag/TCO multilayer electrode was also studied and improved using a developed MATLAB program, where it was found that the transmittances of all studied electrodes exceeded 97%, which is better than what is obtained for ITO. When the developed electrodes applied in the two improved organic solar cells, it was found that the results were improved, and the best performances reached 4.78% and 4.91% for OSC and IOSC, respectively. The optimized multilayer electrode was MoO3(50nm)/Ag(7nm)/MoO3(50nm). As expected, the results are close, but not completely identical, and this difference is due to the nature of the program, the applied physical equations, and the parameters used.