Performance Optimization Of Transparent Electrode In Organic Photovoltaics

Due to the high cost and pollution of conventional semiconductor silicon solar cells' preparation and it's process,prompting researchers put their sights on organic solar cells?OSCs?field.Organic solar cells is rich in raw materials,simple preparation process,roll to roll,massive preparation,etc,it has incomparable advantage with the traditional silicon solar cells.However,compared with inorganic solar cells,OSCs still has low power conversion efficiency.In order to improve the power conversion efficiency of the device,generally the research focus on solar energy photon absorption efficiency.One way is to increase the thickness of the active layer.Another way is to assemble other solar cells by making a translucent OSCs device and having different spectral responses.In this case,we can maximize the use of incident sunlight.At the same time,translucent organic solar cells?OSCs?can be applied to specific living scenes,such as windows with functions of photoelectric conversion.Based on this idea,the anode and cathode of this paper used transparent electrode structure,to prepare the highly efficient translucent organic solar cell devices based on PTB7: PC₇₀ BM structure.The main contents of this thesis are as follows:1.In order to prepare an efficient solar cell,the relationship between the properties of the silver transparent electrode and the preparation parameters was first optimized on the glass substrate,including:introduction of nucleation inducer,using tantalum boat thermal evaporation deposition film,silver deposition rate and the change of the thickness of the silver film.The results show that the critical value of the silver film decreases from 11 nm to 7 nm after introducing the nucleation inducer MoO₃,by this time the deposition rate is 0.9 nm/s and the surface resistance is 41± 8.51 ohm/sq.In addition,with the gradual increase of the deposition rate of silver,the optical and electrical properties of the silver thin films tend to be fine,the evaporation rate is above 0.7 nm/s,the film performance tends to be stable and the performance is not improved?When the thickness of silver thin film reaches 9 nm,the average light transmittance is 74.22% ± 2% in the range of visible light spectrum?400 nm-760 nm?,which is higher than that of other films' thicknesses in this range of the optical spectrum,Then the corresponding surface resistance is 19.68±1.77 ohm/sq?2.In the transparent device,the thickness of the transparent silver film anode is optimized first.The results show that the results of optical and electrical properties to achieve the best compromise when the thickness of the silver thin film is 9 nm?At this time,the efficiency is 2.76%(V_oc = 0.72 V,J_sc = 7.47 mA/cm²,FF = 51%,R_s = 23.42 ?*cm²,R_sh = 873.40 ?*cm²)when the light is incident from the silver transparent electrode;When the light is incident from ITO,the efficiency is 3.94%(V_oc = 0.74 V,J_sc = 8.67 mA/cm²,FF = 62%,R_s = 11.11 ?*cm²,R_sh = 904.65 ?*cm²);The efficiency of light from the silver film electrode is lower than that of the ITO incident,which is the difference in light transmission between the two?3.In order to further improve the transmittance of the film,the outermost layer of the transparent electrode is covered with different thickness of MoO₃,forming a transparent electrode of MoO₃/Ag/MoO₃,and the inner layer MoO₃?2 nm?was formed as a hole buffer layer and nucleation insoles,the outer layer of MoO₃??10 nm?as an light coupling layer to improve the transmission of light,besides that cover MoO₃ to avoid oxidation of the silver layer and prevent the oxidation of the device lead to the attenuation of the device efficiency?By optimizing the PTB7: PC₇₀ BM battery device with a 9nm silver film,the efficiency of the device is optimal when the thickness of the outermost MoO₃ is 20 nm?At this time,the efficiency of the light from the transparent electrode of MoO₃/Ag/ MoO₃ was 3.62%(V_oc = 0.73 V,J_sc = 8.00 mA/cm²,FF = 62%,R_s = 10.74 ?*cm²,R_sh = 1254.55 ?*cm²);When the light is incident from ITO,the efficiency is up to 3.95%(V_oc = 0.72 V,J_sc = 8.53 mA/cm²,FF = 64%,R_s = 10.20 ?*cm²,R_sh = 1246.11 ?*cm²)?The results show that the use of MoO₃/Ag/ MoO₃ as a transparent electrode in the device,effectively improve the efficiency and stability of the device.