Investigation Of Semi-transparent Perovskite Solar Cells With Silver Nanowires Top Electrode

The highest power conversion efficiency（PCE）for inorganic–organic halide perovskite solar cells（PSCs）reported has increased to 24.2%from initial 3.8%in less than a decade.For PSCs,the application prospects are extremely broad,and the building integrated photovoltaic including windows,rooftops or glass curtains that can generate electricity is one of the most important applications.These will inevitably increase the demand for the preparation of efficient and stable semi-transparent perovskite solar cells（ST-PVSCs）.For the preparation of ST-PVSCs,the selection of top electrode is crucial.Untill now,multitudinous transparent conductive electrodes have been widely used in PSCs.Among various transparent electrodes,silver nanowires（AgNWs）electrode is an ideal transparent electrode material because of its excellent photoelectric properties,good flexibility,low cost,and good solution processibility.The preparation of AgNWs electrode by solution method can not only avoid the problems of complicated process,high energy consuming,waste of materials and high cost caused by vacuum evaporation,but also realize large-area preparation of PSCs,which is an excellent choice for the preparation of top electrode of PSCs.However,there are some problems with AgNWs top electrode,such as the poor contact between AgNWs which makes insufficient conductivity,the mismatching work functions between hole transporting layer and AgNWs electrode and poor stability of devices owing to the oxidation and reaction with iodide of silver and so on.Our work takes regular planar structure PSCs,AgNWs and graphene prepared by spraying method as the research objects.By optimizing fabrication parameters of partial functional layers and composite parameters of AgNWs and graphene,we prepared highly efficient and stable ST-PVSCs,and applied them to flexible devices and tandem devices.The specific content includes the following aspects:（1）In the preparation of ST-PVSCs（Structure:FTO/SnO₂/KCsFAMA/Spiro-OMeTAD/AgNWs）,we invesgated the influence of the spray volume of AgNWs dispersion,the concentration of perovskite precursor solution and the spin speed of Spiro-OMeTAD on the transmission and PCE of devices.To balance the transmittance and PCE,the relevant parameters were determined as follows:the spray volume was50μL,the concentration of perovskite precursor solution was 0.7 M and the spin speed of Spiro-OMeTAD was 3000 rpm.Based on these parameters,we obtained a ST-PVSC with an efficiency of 12.28%and an average visible light transmittance（AVT）of22.59%.（2）The effects of reduced graphene oxide（rGO）as modified layer and protective layer on the photoelectric performance of devices were systematically studied.The research shows that the rGO modified layer can play a role in regulating the function between the AgNWs electrode and Spiro-OMeTAD,and connect partially non-overlapping AgNWs to improve the conductivity.In addition,it can also reduce AgI generation as a blocking layer.As for the rGO protective layer,it can not only enhance the contact between AgNWs and greatly improve the conductivity of AgNWs electrode,but also act as a barrier to isolate water and oxygen and effectively inhibit the oxidation of AgNWs.The combined effects have significantly improved the photoelectric conversion efficiency and stability of these devices.A highest PCE of 14.69%with an AVT of 23.3%was achieved for the prepared devices.Moreover,the efficiency can still maintain about 80%of the initial value after 13 days at 40%RH/30℃without encapsulation.（3）Flexible ST-PVSCs with ITO/PET flexible substrate and rGO/AgNWs/rGO top electrode were prepared.The cell devices not only have excellent photoelectric properties,but also have strong bending resistance.In addition,the four-terminal perovskite/silicon tandem solar cells were prepared by mechanical stacking,and the overall efficiency of the tandem devices was up to 20.65%.