Cathode Interface Modification Of Organic Solar Cells

Recent years,organic photovoltaic(OPV)has become a hotspot in the field of solar cell technology owing to its advantages such as light weight,low cost,simple preparation process,application to flexible devices and flexible application.However,the practical application of OPVs still has some disadvantages,such as poor stability,relatively low efficiency and difficulty of preparing in large area.Cathode interface modification is one of the main ways to improve these weaknesses.Due to the high stability and efficiency,the inverted devices are more commonly.In inverted devices,ITO which has high work function,is used as cathode,therefore,the cathode interface modification is very important.In this paper,the effect of cathode interface modification in inverted devices on the performance and preparation process of OPVs was studied.Through the research on the material,preparation methods and treatment of the cathode interface modification layer,we designed interface modification methods with good device performance and low cost.The main research contents include the following three parts:(1)We fabricated devices of inverted structure with a film of C9 as cathode buffer layer.The mechanism of C9 interface layer were studied.The effect of preparation methods and treatment of the cathode interface modification layer were studied at the same time.The experimental results showed that C9 can reduce the work function of ITO cathode effectively,and the buffer layer can be fabricated by self assembly method,the preparing methods is simple.With a P3HT:PC61BM active layer,a 3.76% efficiency was achieved in glass devices,and a 1.57% efficiency was achieved in flexible devices.With a PBDTTT-EFT:PC71BM high-performance active layer,a 7.26% efficiency was achieved.(2)We fabricated devices of inverted structure with a film of H-T as cathode buffer layer.The mechanism of H-T interface layer were studied.The effect of preparation methods and treatment of the cathode interface modification layer were studied at the same time.The experimental results showed that H-T can reduce the work function of ITO cathode effectively,organic polar solvents are more suitable for solution preparation,solvent annealing during the process of self-assembly can improve the device performance.With a P3HT:PC61BM active layer,a 3.19% efficiency was achieved in glass devices,and a 1.46% efficiency was achieved in flexible devices.(3)We fabricated devices with a film of PbOx as cathode buffer layer using a method of UVO treatment after electroplating.The effect of output-current in this method on the performance ofdevices was studied.The experimental results showed that devices using 5mA output-current electroplating for 30 s achieved the best performance.The buffer layer was further treated with NaOH solution.The effect of the concentration of the treating solution on the performance of devices was studied.The experimental results showed that treating the buffer layer with 10mg/ml NaOH solution,can maximize the device performance.With a P3HT:PC61BM active layer,a3.19% efficiency was achieved.