Organic photodiodes (OPDs) have attracted great attention for potential applications in organic optocouplers, image sensors, immune detection and optical communication, due to their advantages of low cost, plenty of functional materials, tunable absorption wavelengths and compatibility with flexible substrates. This article presents an overview of organic photosensitive materials widely used in OPDs, with response spectra regioning from UV to near infra-red. Researches on structure optimization, interface modification, carriers transmission mechanism and internal optical distribution of OPDs are summarized. Some practical applications of the OPDs in optoelectronic fields are also introduced. Finally, an outlook on future development of OPDs is briefly brought up.

Contents
1 Introduction
2 The progress of materials on organic photodiodes
2.1 The materials used in organic photodiodes for visible light
2.2 The materials used in organic photodiodes for UV light
2.3 The materials used in organic photodiodes for near infra-red light
3 The structural optimization and interface modification for the organic photodiodes
3.1 The organic photodiodes with planar heterojunction structure
3.2 The organic photodiodes with bulk heterojunction structure
3.3 The organic photodiodes with other structure
3.4 The research of interface mechanism in organic photodiodes
3.5 The calculation of optical distribution in organic photodiodes
3.6 The stability of organic photodiodes
4 Outlook on future development of organic photodiodes