Synthesis and Photosensitizing Properties of Sublimable Rhenium Diimine Complexes

This dissertation, "Synthesis and Photosensitizing Properties of Sublimable Rhenium Diimine Complexes" by Hei-ling, Wong, 黃喜玲, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled SYNTHESIS AND PHOTOSENSITIZING PROPERTIES OF SUBLIMABLE RHENIUM DIIMINE COMPLEXES Submitted by Wong Hei Ling for the degree of Doctor of Philosophy at The University of Hong Kong in January 2007 Two series of rhenium diimine complexes based on bis(phenylimino)acenaphthene-derived and benzothiazole-derived ligands were synthesized and their uses in fabricating highly efficient photovoltaic devices are presented. The electronic absorption bands, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of these rhenium complexes could be modified easily by changing the structure of ligands. These rhenium complexes were used as the photosensitizers in photovoltaic cells. A series of multilayer bulk heterojunction photovoltaic devices with the device structure ITO/CuPc/Complex: C /C /Al (ITO = indium tin oxide coated glass, 60 60 and CuPc = copper phthalocyanine) based on different rhenium complex photosensitizers co-deposited with C in the active layer was fabricated. ITO 60 serves as the anode and Al as the cathode. CuPc and C were used as the hole and 60 electron transport materials, respectively. The complexes are thermally stable and can be processed by thermal evaporation under high vacuum. Multilayer thin films with very good optical quality and smooth surface morphology were prepared. The effects of varying the hole transport material, thickness of hole transport material, rhenium complex photosensitizer, mixed layer thickness, active layer composition, and light intensity to the performance of the photovoltaic cells were studied systematically. It was found that the short-circuit current (I ) and SC fill-factor (FF) could be significantly affected by varying the device configuration. However no significant change in the open-circuit voltage (V ) was observed., OC For the devices fabricated from rhenium diimine complexes based on bis(phenylimino)acenaphthene-derived ligands, it was found that the highest power conversion efficiency (η ) was achieved for the bulk heterojunction photovoltaic device ITO/CuPc(10 nm)/Complex: C [3:7](125 nm)/C (10 60 60 nm)/Al(60 nm), in which bis(phenylimino)acenaphthene rhenium tricarbonyl chloride was used as the photosensitizer. The highest I and η were measured to SC p be 5.97 mA/cm and 1.40 %, respectively under air mass (AM) 1.5 simulated solar light illumination (100mW/cm ). For the devices fabricated from rhenium diimine complexes based on benzothiazole-derived ligands, it was found that the optimized device structure was ITO/CuPc(10 nm)/Complex: C [4:6](150 60 nm)/C (10 nm)/Al(60 nm), in which 1-(2-benzothiazolyl)isoquinoline rhenium 60 tricarbonyl chloride was used as the photosensitizer. The highest I and η were SC p measured to be 5.71 mA/cm and 1.72 %, respectively. The role of these rhenium complexes in the photosensitization process was studied by measuring the incident photon to current efficiency (IPCE) at different wavelengths. The photocurrent response agreed well with the absorption spectra of the rhenium complexes, CuPc, and C . This suggests that all these compounds are playing important roles as the 60 photosensitizers in the photovoltaic cell and essential to the photovoltaic process. DOI: 10.5353/th_b3786589 Subjects: Rhenium compounds - Synthesis Photosensitizing compounds Photovoltaic