With apparent advantages of low cost, low weight, high flexibility, high efficiency, and high processability in large size device manufacture, organic solar cells (OSCs) have aroused a great deal of attention in current studies of organic electronics all over the world. Especially, the interface structure investigations of acceptor and donor materials in the active layer of OSCs are of particular attraction due to the great influence of micro/nano structures on the photovoltaic performance. The micro/nano structured donor/acceptor interface leads to the enlarged interface area, the reduced distance between acceptor and donor, and the enhanced sunlight absorption, which are favorable to increase the molecular excitation, promote the efficient charge separation and effective exciton dissociation, produce the continuous paths for efficient charge transport, and finally improve the power conversion efficiency (PCE) in OSC applications. In this review, we summarize the recent development of micro/nano interface structured organic solar cells made by various methods in controlling the structures of donor/acceptor interface through nanoimprint lithography, self-assembly technology, solvent evaporation and template methods. The basic principles of these fabrication techniques in producing various micro/nano interface structures, including nano-textured interface, nano-gratings, nanorods array, nanoparticle mediated layer, rough interface and some special patterns, are discussed in detail with particular attention on the effects of the resulted nanostructures on the photovoltaic performance. Further, the current difficulties and future research directions of the micro/nano-structured OSCs are also discussed to give an outlook of the prospect trends and application potentials in modulating photovoltaic devices for high PCEs.

Contents
1 Introduction
2 Effects of micro/nano structures on photovoltaic properties
3 Methods to construct micro/nano interface structures
3.1 Nanoimprint lithography
3.2 Self-assembly technology
3.3 Solvent evaporation
3.4 Template methods
4 Applications of micro/nano structures on solar cells
4.1 Nano-textured interface
4.2 Nano gratings structure
4.3 Nanorods arrays
4.4 Nanoparticles
4.5 Rough interface
4.6 Special patterns
5 Conclusions and perspectives