Aperiodic Porous Metasurface-Mediated Organic Semiconductor Fluorescence

Plasmonic metasurfaces exhibit localized electromagnetic properties that are highly relevant for light management in thin-film organic optoelectronic devices, such as organic light-emitting diodes and organic solar cells. However, the effectiveness of metasurfaces for light management in these devices is complicated by molecular orientation effects. Here, we study how the fluorescence emission from organic semiconducting polymers is modified by aperiodic porous metasurfaces. In particular, we identify the role that polymer molecular orientation plays in enhancing or diminishing the light management ability of the metasurface by comparing local- and large-area fluorescence intensity and fluorescence quantum efficiency enhancements, and by varying viewing angle, for three different semiconducting polymers. We find that the porous metasurfaces improve both the local and large-area quantum efficiency of semiconducting polymer films with more out-of-plane molecular chains by up to 414% and 53%, respectively, compared to planar metal surfaces, by extracting plasmonic surface waves and the Purcell effect. However, there are almost no enhancements to the fluorescence of semiconducting polymer films with predominantly in-plane chains. In fact, in this case, certain porous metasurfaces reduce local- and large-area quantum efficiency by up to 77% and 15%, respectively, due to enhanced ohmic losses. Experimental observations and supporting electromagnetic simulations show that fluorescence modification is also highly sensitive to viewing angle because the emission pattern of each semiconducting polymer is affected differently by the porous metasurfaces. Further, a local excitation enhancement factor of up to 65 is experimentally observed in the case of semiconducting polymer films with more out-of-plane chains and low extinction coefficient on the porous metasurfaces.