| Perovskite materials are widely used in the field of optoelectronics due to their advantages such as high extinction coefficient,bipolar transport and high carrier mobility.Perovskite solar cells(PSCs)have developed rapidly,and its photoelectric conversion efficiency has increased from 3.8%to 25.2%in a short period of ten years.Perovskite solar cells have become the main force of new photovoltaic technologies.Perovskite solar cells with regular structure have been widely studied for their mature preparation process and higher efficiency.Selecting a good electron transport layer is a common method to improve the efficiency and stability of perovskite solar cells.Traditional titanium dioxide(TiO2)is one of the most widely used electron transport layers due to its excellent electron transport properties and large charge transfer interfaces of its mesoporous structure.However,the preparation of Ti02 is complicated.What is more,the nano-particles of TiO2 have a strong photocatalytic effect which makes perovskite decompose easily under ultraviolet light and leads to the degradation of the stability of the battery.Therefore,researchers used other electron transport materials to replace TiO2.Tin dioxide(SnO2)has been widely used in perovskite solar cells because of its advantages of low temperature preparation.The carrier mobility of zinc oxide(ZnO)is higher than that of TiO2 and SnO2.The energy level of ZnO is also matched with the perovskite layer very well.ZnO has become a strong competitor for electron transport materials.Therefore,this thesis intends to prepare aluminum-doped zinc oxide nanowires(AZO NWs)with large specific surface area and high aspect ratio by electrospinning,which were used as composite electron transport layers with low-temperature SnO2 in the PSCs.The use of Al doping increases the carrier concentration of the transport layer,and the nanowire structure increases the contact area between the interfaces,which helps to improve the charge transport and extraction ability,thereby improving the efficiency of the battery.The details of this study are as follows:1.AZO NWs with different Al doping ratios(0-4 mol%)were prepared by optimizing the electrospinning and oxidation processes.The effects of electrospinning and oxidation parameters on the morphology of the nanowires were studied,including PVP concentration,voltage,injection rate,curing distance,relative humidity and temperature,as well as the temperature and time during the oxidation process.When the PVP is 0.7 g,voltage is 11 kV,injection rate is 0.09 mm/min,curing distance is 12 cm,relative humidity is 15%-25%,and temperature is 25℃,the as-spun nanofibers with good morphology were prepared.As-spun nanofibers were calcined at 475℃ for 2 hours,then AZO NWs with smooth and continuous surface,excellent orientation,large aspect ratio of 105 and average diameter of 170±40 nm were obtained.2.Different Al-doped AZO NWs and SnO2 were used as composite electron transport layers in the regular planar heterojunction perovskite solar cells.The effect of adding AZO NWs with different Al-doped ratios on the performance of the device was investigated.The structure of the device was FTO/AZO NWs:SnO2/Perovskite/Spiro-MeOTAD/Ag.The short circuit current density(Jsc)and filler factor(FF)of the perovskite solar cells were increased effectively by AZO NWs.When Al-doped ratio is 2 mol%,the optimal photoelectric conversion efficiency can reach 18.41%,with a 13.15%improvement compared to that of the pure SnO2 layer device.Meanwhile,the hysteresis and stability of the device have also improved.The performance enhancement can be ascribed to the increase of the electron concentration by Al-doping,and the larger interface area of the SnO2/perovskite layer that arises from the nanostructure.The AZO electron transport layer with nanostructures is an effective way to further improve performance of perovskite solar cells. |
PDF Full Text Request