Abstract
In this thesis, we focus on the fabrication and characterization of solution-processed bulk heterojunction and Schottky junction small molecule organic solar cells (SMOSCs). In the first chapter, we briefly review the development of modern photovoltaics, expecially the history of SMOSCs and polymer solar cells. In the second chapter, the operation principles and characteristics of organic solar cells are described, followed by the details of material analysis, device fabrication, and characteristics measurements. In the third part of the thesis, we have studied a series of tailor-made compounds with donor-acceptor-acceptor (D-A-A) molecular structures as donor materials for solution-processed SMOSCs. Spin-coated and blade-coated devices were fabricated and the performance of the devices were further improved by manipulating the donor:acceptor blend ratios. In the fourth chapter, a series of organic A-A-D-A-A compound as donor material has been studied. Solution-processed inverted bulk heterojunction cells were fabricated from the blends of the donors and PC71BM. The opitimized cells showed VOC of 0.99 V, JSC of 8.3 mA/cm2, FF of 0.40, and efficiency up to 3.3%. In the penultimate chapter, we demonstrate a series of small molecule-grafted graphenes as donor material for solution-processed SMOSCs. The opitimized cells showed VOC of 0.72 V, JSC of 8.6 mA/cm2, FF of 0.43, and efficiency as high as 2.7%. This efficiency is among the highest ever reported for organic solar cells based on graphene derivatives as solar active materials. In the last chapter, the solution-processed C70-based organic Schottky junction devices have been fabricated using blade-coating technique. We adopted the co-solvent method in our blade-coated organic Schottky junction devices and the opitimized cells which showed VOC of 0.86 V, JSC of 12.6 mA/cm2, FF of 0.48, and efficiency as high as 5.2% were demostrated.