Influence Of Plasmonic Silver Nanoprisms On Performance Of Organic Photovoltaic Devices

Organic solar cells (OSCs) are attractive due to the advantages of low cost, light weight,mechanical flexibility and suitability for large-area fabrication. However, there are still a fewdisadvantages in OSCs related with the organic photoactive materials. One majordisadvantage is the longer optical absorption lengths compared with charge-carrier diffusionlengths. Although increasing the thickness of the active layer can absorb more light, the powerconversion efficiency usually decreases due to the short charge-carrier diffusion lengths.Introducing plasmonics by incorporating metal nanostructures into organic matrix is apromising approach to solve this problem. Plasmonic structures can improve the absorptionefficiency of the active layers by preferentially scattering and exciting localized surfaceplasmonic resonance (LSPR). The main achievements obtained are summarized as follows:Firstly, we used a two-step sunthesis technique to synthesize silver nanosprisms (AgNPs).The findings suggest that the morphology and size of the AgNPs are key factors with the addquantity of seed solution. Different shapes and sizes of AgNPs were also with differentplasma resonance absorption.Secondly, the AgNPs were adsorbed on the ITO to assemble a complete solar cell with astructure of ITO/AgNPs/PEDOT:PSS/P3HT:PCBM/LiF/Al. We used the AgNPs for twogroups of experiments: differernt resonance absorption peak and different adsorption timesrespectively. The results show that AgNPs can improve the PCE of OSC which is notmodulated by optical-field distribution but is ascribed to their SPRs. We study the Effects ofthe position of AgNPs on the performance of organic solar cells. The results suggest that weshould think over the following three factors when considering the function of silverplasmons:(1) Whether or not they produce absorption shadows to affect the absorption oflight in the active layer;(2) whether or not they affect the carrier transport; and (3)whether ornot they impact the interfacial contact. Only when all these factors are considered can wemake out the effect of metal plasmons ondevice performances.Thirdly, we study the influence of1nm thickness gold layer on the performance of thedevice. The structure is ITO/Au (with and without nanosheets)/PEDOT:PSS/P3HT:PCBM/LiF/Al. After incorporated the gold particles, the light transmittance were not affected. But,the nanosheets array were uneven growth to increased surface roughness and the devicepreformance were reduced.