Study On Interface Modification Effectting On The Performance Of Organic Solar Cells

As the environmental problems are getting worse today,organic solar cell gets more and more attention and has been developing rapidly in the recent 20 years.Organic solar cell has many advantages such as simple preparation process,low cost of preparation,easy to get flexible devices,etc.However,there are many unresolved problems such as low energy conversion efficiency,short lifetime and the unclear physical mechanism so that there will be a long way to put it into commercial production.The interface modification is one of the most important factors that affects the lifetime and photovoltaic performance of device.In order to improve the energy conversion efficiency of organic solar cell,this paper focuses on the structure design of device and the optimization of interface modification layer.The interface modification effect on performance of organic solar cells is systematically studied.The contents of this paper include the following four aspects:(1)The performance of small molecule organic solar cell with Mg:Ca:Al alloy cathode is studied and the energy conversion efficienciy of device is optimized by changing Mg doping ratio in alloy cathode.In order to study the effect on the performance of devices,whose cathode buffer layer is BPhen,the thickness of the cathode buffer layer is changed.Because of BPhen as cathode buffer layer,a good contact is formed between the active layer and the metal cathode,so the transmission ability of electron carrier ability and the collection ability of cathode have been improved,which will make the photoproduction excitons quenching reduce and the photovoltaic performance of devices improve.The organic solar cell with 10 nm BPhen as cathode buffer layer obtains the maximum energy conversion efficiency of 0.96%,which is 88.24% higher than that of the contrast devices.(2)The performance of bulk heterojunction organic solar cells with CuPc:C60 and NPB:C60 structures are studied.The experiments show that the bulk heterojunction device performs much better than the planar heterojunction organic solar cell.The performances of the devices are optimized by changing the doping ratio of CuPc and NPB in mixed layer.The influence of the heterojunction organic solar cells,whose cathode buffer layers are BPhen,is studied by changing thickness of the film.The experiments show that BPhen as cathode buffer layer plays an important role in blocking excitons,which will make photoproduction excitons quenching reduce and the performance of devices effectively improve.The introduction of the cathode buffer layer improves the energy conversion efficiency of bulk heterojunction organic solar cell with Cu Pc/CuPc:C60/C60 structure from 0.28% to 0.63%.The cathode buffer layer improves the energy conversion efficiency of bulk heterojunction organic solar cell with CuPc/NPB:C60/C60 structure from 0.24% to 0.40%.(3)The performance of organic solar cells with Alq3 as the cathode buffer layer is studied.Alq3 is verified having a good electron transfer capability by the experiments.The introduction of Alq3 as the cathode buffer layer makes the performance of organic solar cell better.A stable contact between the metal cathode and the active layer is formed and the work function of cathode is reduced,so that the transmission efficiency of the electronic is improved.The experiment result shows that with the 3 nm Alq3 film,the device achieves maximum energy conversion efficiency of 0.48%.The open circuit voltage of the device is 0.25 V;fill factor is 0.47;short circuit current is 4.03 mA·cm-2.(4)The performance of small molecule organic solar cells with NPB,MoO3 and V2O5 as the anode buffer layer is studied.The experiments results show that introduction of NPB and MoO3 do not improve photovoltaic performance of the devices.However,V2O5 film reduces the surface roughness of ITO and forms ohmic contact between the anode and the active layer so that the open circuit voltage of the device increases.At the same time,the V2O5 as anode buffer layer effectively restrains the leakage current and reduces the compound probability of carrier,thus the short circuit current of the organic solar cell is improved.The experiment result shows that when the thickness of V2O5 film is 5 nm,the organic solar cell achieves maximum energy conversion efficiency of 0.79%,which correspondes to a 25.4% increase compared with the device without adding anode buffer layer.