NaYF₄:Er³⁺（2%）,Yb³⁺（18%）Up-conversion Nanoparticles And Their Application In Polymer Solar Cells

Organic photovoltaic cells (OPVs) are considered as a highly promising candidate in the fieldof photovoltaic device due to low cost, light weight, easy fabrication, mechanic flexibility, andsuitable for production of large scale. We summary the researches of all the world on polymersolar cells, especially bulk hetero-junction polymer solar cells, meanwhile, putting emphasis onthe effect factors on the performance of polymer solar cells.To overcome the low power conversion efficiency (PCE) of polymer solar cell mainly causedby the limited absorption of the active materials P3HT, we introduce up-conversion material((NaYF4:Er3+(2%), Yb3+(18%)) which can convert near-infrared (NIR) radiation into green andred emissions to poly(3-hexylthiophene)(P3HT):[6,6] phenyl C61butyric acid methyl este(PCBM) solar cell. But, up-conversion (UC) efficiency is so low that the actual effect of UC ondevice performance need tobe further explored.Oil-soluble and water-soluble NaYF4:Er3+(2%),Yb3+(18%) up-conversion nanoparticles (NPs)with sizes of20nm and70nm were respectively synthesized and incorporated into thepoly(3,4-ethylenedioxythiophene) with poly(4-styrenesulfonate)(PEDOT:PSS) hole extractionlayer in bulk heterojunction OPVs based on the polymer P3HT. The OPVs incorporated with70nm UC NPs exhibit a higher performance with enhancement factors of9.9%for short-circuitcurrent density and8.2%for PCE over the control devices, compared to8.9%and6.5%in20nmUC NPs-incorporated OPVs. Both the influences of the UC NP’s emission, scattering, andresolvent on cell’s performances are investigated and results reveal that NP’s photoluminescencecontributes little to device performance enhancement. In contrast, the main impact factors onperformance include UC NP’s resolvent, scattering, the UC NPs-induced roughness andelectrical conductivity change of PEDOT:PSS. The higher performances in UCNPs70-incorporated OPVs are mainly attributed to a larger scattering, the rougher surface ofPEDOT:PSS and a negligibly negative effect of the ethanol resolvent.