There are still a lot of parameters to be optimized in the organic solar cells to become more economically efficient than silicon solar cells. We address in this book many effective points as a contribution for developing organic solar cells towards best performance. Our contributions in this book can lead to: 1) improvement in charge carrier transfer in the solar cell active layer through the use of 9,10-diphenylanthracene conjugated dye as a third material, 2) improvement in light harvesting and photocurrent of the solar cell through the use of coumarin 6 laser dye as a third material, 3) increasing the knowledge of properties and behavior of materials combined in new solar cell system, 4) understand the device physics and locate a relationship between production parameters and performance parameters of solar cell based on small-organic dye and fullerene derivative through investigation of device performance under different production parameters, and 5) illustration the pronounced impact of organic/organic interface on the absorption of active layer and therefore on the generated photocurrent of the organic solar cell.