Spray-pyrolysis Deposited NiO_x Thin Film With Low Temperature And The Corresponding Application In Flexible Perovskite Solar Cells

As facing the future challenge of energy demand,solar energy is one of most promsing renewable energeis.Due to the excellent photoelectrical properties of the perovskite materials and the low-cost manufacture,Perovskite solar cells?PSC?has beconmed a rising photovoltaic technology with great potential In the last ten years,the efficiency of PSC is increasing exponentially,and has ready been up to 23%^[1].Flexible PSC has the high power-weight retio,good resistance to bending and reduced cost,and they are also suitable for roll-to-roll technology,which let them show a great potential for all kind of applications,like integrated with unmanned aerial vehicle.However,the manufactures of PSC are usually related to high-temperature process,which can not be applied onto normal plastic substrate.In addiation,when exposured by the organic-inorganic hybrid perovskite materials,which usually be used in PSC,are easily decomposed.That leads to the need to use an efficient method to encapsulate the devices.In this work,a low-temperature method to deposite the NiO_x thin film will be discussed,and applied into flexible PSC:?1?Firstly,this work has introduced the combustion method to reduce the temperature of the NiO_x film prepared by spray pyrolysis,and then improved the performance of the NiO_x film by Mg doping.The NiO_x films prepared by low-temperature spray pyrolysis show good crystallinity,optical transparency and flatness.And by a small amount of doping Mg?5 at%?,the valence band edges of NiO_x has been deepened which promotes the carrier extraction and transport capability between the NiO_x film and the perovskite film.Then,the NiO_x films deposited by low-twmperature spray pyrolysis have been applied into the inverted PSC with the structure of Glass/ITO/Mg:NiO_x/MAPbI₃/PCBM/BCP/Ag.It can be seen that with the increase of Mg doping amount,the open circuit voltage of the devices are gradually increased.When the doping amount is 5 at%,the device has the highest power conversion efficiency?PCE?reaches 17.68%,with the highest short-circuit current density.?2?Then,the Mg:NiO_x films deposited by low-twmperature spray pyrolysis have been applied into the flexible PSC.The Mica/ITO substrate exhibits a similar light transmittance as the Glass/ITO substrate and the superior temperature resistance compared to the plastic flexible substrate.The flexible PSC show a little reduced efficiency compared to the rigid devices,but still has obtained the open circuit voltage of 1.046 V,and the short circuit current density of 21.03 mA/cm²,the fill factor of 77%and the PCE of 16.9%.The flexible devices prepared in this work can maintain relatively high PCE even after multiple bendings.In addiation,after efficient encapsulation,the flexible devices can maintain high stability under long-term continuous illumination and high relative humidity condition.It is indicated that the encapsulated flexible devices can effectively overcome the eroding from the external environment,and have a long-term physical and chemical stability.