Synthesis of Polymer Solar Cell using n-Type Perylene Bisimide Derivatives and p-Type Oligo(p-phenylene vinylene)s

Citation: Albertus P. H. J. Schenning, E. W. Meijer (2004/07/13) Synthesis of Polymer Solar Cell using n-Type Perylene Bisimide Derivatives and p-Type Oligo(p-phenylene vinylene)s. J. AM. CHEM. SOC. 2004, 126, 10021-10027 (RSS)
DOI (original publisher): 10.1021/ja048819q
Semantic Scholar (metadata): 10.1021/ja048819q
Sci-Hub (fulltext): 10.1021/ja048819q
Internet Archive Scholar (search for fulltext): Synthesis of Polymer Solar Cell using n-Type Perylene Bisimide Derivatives and p-Type Oligo(p-phenylene vinylene)s
Download: http://pubs.acs.org/doi/pdf/10.1021/ja048819q
Tagged: Chemistry (RSS)

Summary

A polymer solar cell is a type of flexible solar cell made with polymers, that produce electricity from sunlight by the photovoltic effect. Currently, most commercial solar cells are made from a refined highly purified silicon crystal, similar to the material used in the manufacture of integrated circuits and computer chips (wafer silicon) The high cost of these silicon solar cells and their complex production process has generated interest in developing alternative photovoltaic technologies. Polymer solar cells (PSC) is one of the possible replacements. These solar cells add some very interesting properties to the solar cell as well as reducing the price considerably. Polymer solar cell generally consist of five layers: Glass, ITO, PEDOT: PSS, active layer, calcium and aluminium. The glass serves as a supporting layer for the solar cell and the only demand glass has to fulfil is that it does not absorb light in the visible area, since the solar cell uses this light to generate power. Other and more flexible types of supporting layers, like transparent polymers, can also be used. ITO (indium tin oxide) and aluminium serves as the electrodes in the solar cell. Beyond that, the ITO and aluminium are also used to generate a built-in electric field caused by the difference in the metals’ work functions. This electric field is used dissociate the excitons, which are generated when the active layer absorbs light, and afterwards to pull the charge carriers out from the active layer. Like glass the ITO layer is transparent in the visible area. PEDOT:PSS (poly[3,4-(ethylenedioxy)-thiophene]:poly(styrene sulfonate)) and calcium are two materials which are introduced into the solar cell in order to increase the built-in electric field and thereby improve the performance of the solar cell. The active layer in this polymer solar cell consists of a donor-acceptor system. Different types of systems are present like P3HT, MEH-PPV, CN-PPV, OPV, FT8BT are being used as donor and PCBM , perylenebisimide , diketopyroll are being used as acceptor. For donor system OPV (oligo(p-phenylene vinylene)) is well reported . In active layer made from OPV, OPV is the donor part of the active layer and perylene derivative is acceptor. In the simplest polymer solar cell, the polymer layer is sandwiched between two metals forming a hetro-junction. The two metals establish an electric field inside the polymer caused by their asymmetrical work functions.Four different (chiral) electron-deficient (n-type) perylene bisimides containing aliphatic, aromatic, or ethyleneoxide side chaines can be used. All of them form supramolecular stacks in apolar methylcyclohexane (MCH) solution as demonstrated by concentration- and temperature-dependent absorption, circular dichroism, and fluorescence studies. One derivative was investigated in more detail in the solid state and proven to be liquid crystalline and capable of forming nanometer-sized fiberlike networks when drop-cast from MCH. Optical spectroscopy techniques show that perylene bisimide and an oligo(p-phenylene vinylene) (p-type) derivative orthogonally self-assemble into separate nanosized p-and n-type stacks in MCH. In contrast in toluene only molecularly dissolved species are present. In films deposited from MCH as well as from toluene photoinduced electron transfer takes place from the p-type material to the n-type material. As a result of the orthogonal self-assembly process, in films from MCH an ordered network of fibers was formed, whereas in films from toluene no ordering was observed. However, probably due to the lateral orientation on the surface and the presence of long aliphatic chains pointing toward the electrodes, efficient bulk heterojunction solar cells could not be constructed. Supramolecular stacks of perylene bisimides have been obtained in a polar solution as demonstrated by concentration and temperature-dependent absorption, circular dichroism, and fluorescence studies in methylcyclohexane (MCH). Furthermore these derivatives are capable of forming nanometer-sized fiberlike networks when drop-cast from MCH. By optical spectroscopy techniques, it was demonstrated that in MCH separate stacks of perylene bisimides and oligo(p-phenylene vinylene) (p-type) can be formed, whereas in toluene only molecularly dissolved species are present. In the solid state, charges were created in films deposited from MCH as well as from toluene. In films from MCH an ordered network of fibers was formed, whereas in films from toluene no ordering was observed. Bulk heterojunction solar cells of these mixed films show poor performance, which is probably due to the lateral orientation of the stacks on the surface. Therefore, for improving the device characteristics, it seems essential to vertically align the supramolecular stacks in thin films.