Design Of Transparent Nanofibrous Film Electrode And Application For Solar Cells

In recent years,it has been great development in wearable electronic devices.Various kinds of wearable devices have been applied in our life,which is improving our working quality and living standard.However,the wearable power source cannot meet such as lightweight,comfortable,high endurance and many other requirements.Therefore,the wearable power source is is one of the key constraints of the wearable electronic devices.Solar cells can convert solar energy into electric energy without geographical restrictions,and the energy is convenient and green.Fabric is the best wearable carrier.As a result,it has great development potential to assemble the wearable power source by the solar cell loading on the fabric.However,it is difficult for the current wearable flexible solar cells to meet the requirements of high efficiency,stability and flexibility.The key is that the photoconductive electrode of the fabric solar cell must have the properties of electrical conductivity,light transmittance and flexibility.This directly affects the performance and quality of the solar cells fabricated using the photoelectrode.Therefore,it is fundamental and important to develop flexible transparent electrode for wearable photovoltaic devices.Now,the conventional indium tin oxide（ITO）electrode is always used as flexible electrode for solar cells.However,the ITO electrode is not suitable for flexible solar cells as ITO forms cracks easily by small stretching or bending.Therefore,the flexible transparent electrode has attracted much attention.In this paper,flexible Ag/PI/PU nanofibrous film electrode was prepared by electrospinning and magnetron sputtering.The average diameter of PU nanofibers is about 427nm,and that of PI nanofibers is about 167nm.With the increase of PI proportion in the nanofibers,the diameter of the nanofibers is gradually decreased.For PI/PU=10/90,the average diameter of PI/PU nanofibers is about 353nm.After deposited silver particles of 520s by magnetron sputtering,the average diameter of the nanofibers is 346nm.With the increase of PI,the elongation at break is decreased,the tensile strength and the initial modulus are increased.When the proportion of PI is10%,the tensile strength and elongation of the Ag/PI/PU nanofibrous film is 15.4MPa and 161%,respectively.Besides,the nanofibrous film has the largest strain energy.With increase of electrospinning duration and magnetron sputtering time,both the transmittance and sheet resistance are decreased.After optimization of electrospinning duration and magnetron sputtering time,when electrospinning duration is 60s,magnetron sputtering time is 520s,the transmittance and sheet resistance of the flexible electrode is 80.8%and 21.8Ω/□.Besides,the flexible electrode demonstrated well mechanical stability with the resistivity of 24.6Ω·cm under tensile strain of 160%.With 100%tensile strain,the transmittance is decreased to 77.2%,and the relative resistivity is increased to 0.11 over 49 tensile cycles.To optimize incident light spectrum in solar cells,Y₂O₃:Eu³⁺and Y₂O₃:Tb³⁺phosphor nanoparticles were introduced into the nanofibers.With addition of phosphor,the morphology of the nanofibrous film is not changed,but the nanofibrous film performs fluorescent effect of converting ultraviolet（UV）light to visible light.With the increased weight of phosphor in the nanofibers,the peaks intensity performs parabolic change.After optimization of the proportion of Y₂O₃:Eu³⁺and Y₂O₃:Tb³⁺,when(Y₂O₃:Eu³⁺)/(Y₂O₃:Tb³⁺)/（polymer）=0.2/0.2/1,the fluorescence intensity of the nanofibrous film is largest.When electrospinning duration is 60s,magnetron sputtering time is 520s,the transmittance and sheet resistance of the flexible fluorescencent electrode is 80.3%and 22.1Ω/□,respectively.With tensile strain of 100%,the transmittance is decreased to 76.8%.When the tensile strain is 140%,the resistivity is increased to 20.5Ω·cm.The perovskite solar cells were fabricated on different flexible electrode.The surface morphology of perovskite layer is not significantly different deposited on different nanofibrous film substrates,and the average diameter of the perovskite particles is about 430nm.Besides,the PV parameters are almost same of the solar cells fabricated on the flexible electrode without phosphor:the open circuit voltage is about 0.8V,the short circuit current is about 6.1m A/cm²,the filling factor is about 44%～48%,and the power conversion efficiency（PCE）is about 2.3%.With addition of phosphor,the short-circuit current and PCE are improved to 7.2 m A·cm^-2and2.65%,respectively.Furthermore,both the current output stability and electrochemical impedance of the solar cells have been improved and optimized.However,both the solar cells fabricated on Ag/PI/PU and Ag/phosphor/PI/PU flexible electrode have terrible bending stability.As bending radius of 1mm,after 8 cycles,PCE of both the solar cells are less than 1%.