Organic thin-film solar cells are cheaper, lighter and more flexible than current solar cells, and are easily scaled up by utilizing wet processes such as ink-jet printing and roll-to-roll printing techniques. The inverted-type organic thin-film solar cells developed by Kanazawa University display high durability and resistance to corrosion. In order to enhance their potential to the level of commercial application, we strongly promote the basic researches on the novel organic materials (especially conjugated polymers) and the developments of device-processing techniques in the atmosphere, which can markedly restrain the process energy. In this presentation, we will introduce the current situation and challenges of organic thin-film solar cells focusing on our research.