Application Of Active Layer Doping And Cathode Modification In Polymer Solar Cells

This work is focused on the polymer solar cells based on the blend of poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM). The main contents include three parts:polycyclic aromatic hydrocarbons doping active layer, graphdiyne doping active layer, and the effect of small organic molecules modification layer on photovoltaic devices. The main results are shown as follows.1.Four kinds of polycyclic aromatic hydrocarbons (pentacene, perylene, phenanthrene, pyrene) doped in the P3HT:PCBM active layer with various ratio (doping range from0%-1.5%).Improved short-circuit current and other properties were obtained in appropriate doping ratio. The doping ratio has strong impact on Jsc of photovoltaic devices, the infulence to the open circuit voltage and fill factor is relatively small. It was found that the morphology of active lyare after doping is nearly unchange under small doping ratio (less than1%). The improved efficiency due to the level matching which lead to higher efficiency of the photogenerated exciton dissociation in the active layer.2.Graphdiyne was introduced in P3HT:PCBM active layer, when graphdiyne replace PCBM as acceptor, there is no obvious photoelectric response, when graphdiyne doping in P3HT:PCBM active layer, Jsc can be enhanced by varying the doping ratio. By analyzing the absorption spectra, external quantum efficiency and dark current, It is found that stable two-dimensional sheet of graphdiyne has no energy transfer with P3HT. The improvement in the performance is due to high charge transport capability of graphdiyne and the formation of good charge transport channels in P3HT:PCBM network.3.Cathode modification with small organic molecules in polymer photovoltaic devices have been studied. Three small organic molecular materials (PBD, Alq3, Zn (BTZ)2), which have high electron transport properties, were introduced in photovoltaic devices. By analyzing current-voltage curve, energy level, dark current, cathode modification with small molecules can make the device's built-in potential increased, lead to Voc increased. The decline of Jsc is due to electrons and holes recombination in small molecules layer.The effect of cathode modification with these three small molecules have been compared, also the reasons has been discussed.