TECHNICAL REPORT

Abstract

Cadmium selenide nanoparticles and nanoclusters were prepared and added to polymer solar cells to improve their photon capture ability. These nanoparticles did exhibit some beneficial effects on the photon conversion efficiencies of selected polymer solar cells. Ternary bulk heterojunction systems based on composites of methyl viologen-doped, CdSe nanoparticles blended with poly (3-hexothiopene) (P3HT) and 6, 6-phenyl C{sub 61}-butyric acid methyl ester (PCBM) were also tested. It was found that the devices with methyl viologen-doped CdSe nanoparticles do produce more photocurrent in a region surrounding the absorption peak of the particles (560 to 660nm) when compared to pristine P3HT:PCBM devices. Gold nanorods were also prepared and tested in some solar cells. These nanorods did produce a very small enhancement in photon absorbance, but the observed increase the photon conversion efficiency was not sufficient to make the effort worthwhile. Our goals were (1) to prepare cadmium sulfide and cadmium selenide clusters and nanoparticles to be tested as photon absorbers to enhance the photon conversion efficiency of polymer solar polymer solar cells and (2) to prepare gold and silver nanorods to be added to polymer solar cells to enhance their photon capture capability. The cadmium sulfide and cadmium selenide nanoparticles and some new nanoclusters were prepared. The cadmium selenide nanoparticles were also tested in solar cells and did exhibit some positive effects when they were combined with certain co-absorbing polymers. Due to solubility problems that were not solved in the available time, the new nanoclusters were not tested in solar cells. Ternary bulk heterojunction systems based on composites of methyl viologen doped, CdSe nanoparticles blended with poly (3-hexothiopene) (P3HT) and 6, 6-phenyl C61-butyric acid methyl ester (PCBM) have been examined in detail. The methyl viologen was added to promote charge separation of the initially formed excitons. It was found that the devices with CdSe produce more photocurrent in a region surrounding the absorption peak of the particles (560 to 660nm) when compared to a pristine P3HT:PCBM device. Gold nanorods were prepared and tested in some solar cells. These did show a very small enhancement in photon absorbance. However, the increase in short circuit current was negligible, which suggests that this antenna effect produces no significant increase in photocurrent generation. Efforts to synthesize niobium-doped zinc oxide nanoparticles for use in polymer solar polymer solar cells were also made. The nanoparticles were prepared, but they were not tested in the cells before the termination of the funding of the project.