the development of photosensitive organic materials has attracted tremendous attention during recent years [1-5]. Indeed, as these materials are mostly composed of polymers, they can essentially be deposited by low cost solution-based processes, such as spin coating, dip coating, or inkjet printing [1][3]. The earliest and potentially most significant applications of these materials are photovoltaic cells [1-5] and, to a lesser extent, organic photodetectors [6-7]. These organic devices have shown great potential to become flexible, printable, low-cost and light-weight products. Moreover, these organic materials can be deposited on large surfaces, which is usually not possible using more conventional crystalline semiconductors. Similarly, a considerable effort has been dedicated to the analysis and modelling of the operation, performances and limitations of these devices. The aim of this paper is twofold: first, the state of the art and main trends of the understanding, modelling and simulation of such devices, focusing on the Bulk HeteroJunction (BHJ) polymer based devices, will be reviewed. In a second part, recent finding, combining experiments and modelling (numerical as well as analytical) will also be presented.