Research On Optimization Method Of Device Based On The Novel DPP Polymer Thick Film Solar Cells

Solar energy is one of the cleanest renewable energy sources and the development of solar photovoltaic industry is very important to solve the energy crisis and ecological environment.Especially,polymer solar cells(PSCs)have the potential advantages in the photoelectric conversion efficiency and large-scale applications due to its low cost,light weight,high tunability,and easy fabrication over large and flexible substrates.PSCs have developed rapidly and energy conversion efficiency(PCE)has exceeded 10%,so commercialization of PSCs is imminent.At present,BHJ solar cells research is the most extensive,which is because the active layer blended with polymer donor and fullerene derivatives acceptor can effectively promote exciton dissociation.However,the thickness of optimized PSCs active layer is usually around 100 nm.The thin active layer not only affects the light absorption efficiency of the material,also its small changes in thickness have great influence on the efficiency and stability of the devices.As a result,the printing or roll-to-roll process in the production of large areas has been limited and also restricts PCE of the PSCs.In this paper,the effect of the traditional device optimization methods on the thickness of the active layer is studied by using the new DPP-type polymer material with wide spectral and high carrier mobility.It is expected to discuss the best active layer PSCs optimization process and analysis the mechanism of optimization process in thick BHJ films.The main research work is as follows:1.The effects of optimization process,including donor/acceptor ratio,additives and SVA on the photoelectric properties of PSCs were investigated by using PBDT-FB-DPP polymer materials.The results showed that the best active layer thickness of the PSCs devices based on PBDT-FB-DPPPC60 BM is around100 nm,the PCE can reach 2.73%,the optimal donor/acceptor ratio of PSCs is1:2,the optimum concentration of DIO is 5 vol%,and the best time for methanol vapor annealing is 30 s.In addition,we found that additive DIO and methanol vapor annealing have improved the photoelectric properties of the devices,while their mechanism of action are not the same.2.Combined with PDPP-T-TT polymer materials,four BHJ optimization processes including solvent additives,mixed solvents,solvent vapor annealing and solid additive BPO were studied in thick active layer PSCs.We found that solvent additives,mixed solvents and solvent vapor annealing can effectively improve the photoelectric properties of the device,through a series of process optimization the PCE can be increased from 1.41% to 3.47%,Jsc increased from2.97 mA·cm-2 to 9.90 mA·cm-2.What’s more,the solvent additives DIO and CN can increase the thickness of active layer from about 90 nm to nearly 300 nm,while the effect of solvent vapor annealing on improving the thickness of the active layer is much lower,which can improve the thickness of the film from250 nm to 270 nm.In addition,the effects of solvent vapor annealing on the optical and electrical properties were investigated to analysis the root causes for the improvement of Jsc.3.The ternary blend PSCs were prepared by adding the novel random polymer PBDT-DFB-DPP as the component to the binary P3HT: PC60 BM devices,expected that the absorption spectrum of the device will be broadened.Although the results were not as good as expected,the electrical properties of the devices in the ternary blend cells were analyzed through hole-only devices and hole mobilities.It was found that the addition of PBDT-DFB-DPP result a significant decrease in the hole mobility of the ternary blend devices,and the more the component was added,the more the hole mobility would decline,which is the direct cause of the decrease of photoelectric performance.