Structure And Properties Of The Active Layer In Organic Polymer Solar Cell

In the past few years, the conjugated polymer: small molecular bulk heterojunction solar cells have been subject to increasing interest. Since the discover of the morphology of conjugated polymer: small molecular blends film being crucial to the efficient of organic polymer solar cells in 2001, a lot of effort towards studying between morphology and efficiency in the conjugated polymer: small molecular bulk heterojunction solar cells has been made.In this paper, we reviewed the progress on organic polymer solar cell, discussed the mechanism and structure of organic polymer solar cell, then we also introduced the progress on morphology and efficiency of organic polymer solar cell. The morphology of MEH- PPV: EP-PTC blend films has been comprehensively studied using AFM. The results show that the phase separation in the blend film based on non-aromatic solvents is in micron size, while the phase separation in the blend film based on aromatic solvents is in nano-size; the dimension of the phase separation increases with the increase of the EP-PTC content and the total solution concentration; and increasing the annealing temperature the coalescing extent of the EP-PTC clusters is improved.To study the relation between the morphology and device properties, the solar cells based on MEH-PPV: EP-PTC as the active layer with different solvent and blending ratio was prepared. Compared to non-aromatic solvents, the phase separation in the blend film based on aromatic solvents is in nano-size, which increases the interface area of the two phases obviously and subsequently increases the efficiency of charge separation.The power conversion efficiency of solar cells based on MEH-PPV: EP-PTC blend film from chlorobenzene solvent is 0.0621%, which is improved 20 times of magnitude comparing with that of solar cell based on the blend film from tetrahydrofuran solvent.To improve the performance of the bulk heterojunction solar cells, we combining the high efficiency of charge transport of the bilayer heterojunction with the high efficiency of charge generation of the bulk heterojunction, interpenetrating heterojunction devices based on MEH-PPV: PCBM has been designed and manipulated. The results from AFM, UV-vis and PL show, for the active layer (the thickness is 150nm) of interpenetrating heterojunction devices, the surface between MEH-PPV and PCBM is that PCBMs are interpenetrated into MEH-PPV matrix and the thickness of the interpenetrating layer is about 110nm, but not interpenetrated completely, while the surfaces between the active layer and electrodes is the MEH-PPV and PCBM domains comparatively. So the interpenetrating heterojunction devices consist of a large interface area between the donor and acceptor with connecting paths to the respective electrodes for both D/A materials at the same time, which ensure effectively separating of exciton and the high efficiency of charge transport and charge collection to enchance the performance of the interpenetrating heterojunction devices. The power energy efficiency of the interpenetrating heterojunction device is to 2.68%, which is improved 14 times of magnitude comparing with that of solar cell based on double layer and 3.4 times of magnitude comparing with that of bulk heterojunction solar cell based on MEH-PPV: PCBM(1:1) and 2 times of magnitude comparing with that of bulk heterojunction solar cell based on MEH-PPV: PCBM(1:4).