Study On The Influence Of Substrate Conductivity On The Performance Of Large Area Solar Cell Device

With the improvement of science technology and development of society,under the effect of environment pollution and energy crisis,organic solar cells become the new next type green energy instead of traditional fossil fuel.It comes into people’s vision step by step.Up to date,small scale organic solar cells（effective area about 0.1 cm²）makes a spurt of progress.By synthetizing new efficient organic photoelectric materials,designing electrode structure,regulating of interface modification layer,power conversion efficiency has got a qualitative leap,getting close to 15%of the happy results.Compared with traditional inorganic silicon solar cell,organic solar cells have so many advantages,such as,lower cost of production,simple preparation process,roll to roll processing,good flexibility,adjustable absorptive spectrum and so on.The research on small scale devices is relatively perfect,and it has the potential for small-scale commercial applications.But the research on large scale organic solar cell devices is still in the starting step.According to the existing experimental results,the results show that after simplifying enlarge the effective area of the device,the performance parameters of the device appears a large cut.The reason of the power conversion efficiency losing is that:1.When the effective area of the device is magnified,conductivity of the transparent electrode ITO declines quickly,making the resistance of the transparent electrode rise obviously,increasing the heat loss of the device.Due to the decrease of the conductivity of the substrate and the distance between the charge and the electrode is further,charge collection efficiency is decreased;2.Due to the effective area of the device is magnified,the thickness of the organic active layer and the interface modified layer is thinner（the thickness only has several hundred nanometers）,in the process of spin-coating,the difference of centrifugal force in different positions makes the film uniformity,and pinholes and burrs make the quality of the films have so many defects.In the second chapter,we study using PTB7-Th:PCBM as organic active layer to make different effective area（0.16 cm²—0.97 cm²—2 cm²）organic solar cells,and using impedance spectroscopy and simulating equivalent circuit of device to analyze the reason of decrease of large scale organic solar cells power conversion efficiency:Parallel resistance（Rp）of the devices become smaller,when the effective area of the devices turns to large;then,we solve the problem of substrate conductivity of large scale organic solar cells by using high conductivity transparent electrode ITO and special patterned electrode structure.At last,we improve the performance parameter of large scale organic solar cells.Power conversion efficiency improved from 4.75%to 6.54%.In the third chapter,we use PCDTBT:PCBM as active layer to make organic solar cells using UTMF-Ag as transparent conductive electrode.Firstly,we confirmed to use 15 nm Ag film as transparent conductive electrode by comparing the Transmittance and conductivity of different thickness Ag film.In the consideration of metal film transmittance and conductivity,we prepared organic solar cells device based on ultra-thin metal Ag film.Photoelectric performance parameters of the OPV is:Voc=0.93 V;current density Jsc=8.25 mA/cm^-2;filling factor FF=50%;Power conversion efficiency PCE=3.75%.In general through the above research,we find that the poor performance of large area devices is due to poor conductivity of ITO substrates.When the effective area of the device increases,the series resistance of the electrode increases.Further studies have shown that the use of highly conductive ITO and special patterned electrode structures can improve the performance of large area devices in varying degrees.At the same time,by using metal silver film instead of ITO as a transparent electrode to produce organic solar cell devices,it also solves the problem of substrate conductivity in large area to a certain extent.