Interfacial Engineering And Stablility Study For Solution-Processed Organic And Perovskite Solar Cells

Comparing with slicon materials, solution processed solar materials attracted growing interesting for the advantage of flexible, light weight, low temperature fabrication, wide range colour and certain transparency. More and more people are turning to solution processed solar cell. As is known to all, polymer solar cell and perovskite solar recently play a key role in the solution processed solar cell field. The photo conversion efficiency(PCE) of organic solar cell has reached about 11.5%. Meanwhile, PCE over 20% has been reported for perovskite solar cells. However, problems are still exist with the rapid advance of the PCEs. Such as the hygroscopicity and corrison nature of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS) lead to the degradation of the device. It is urgent to find a stable materials as interfacial layer.Firstly, graphene oxide nanoribbion(GONR) hybridized with carbon nanotubes(CNTs)(GONR/CNTs) were used as interfacial layer in organic solar cells. Solution processible GONR with continuously one-dimensional length and remaining CNTs have been synthesized by partially unzipping from multiwalled carbon nanotubes(MWCNTs). Such low-cost GONR/CNTs show solution processibility as well as tunable work function and multifunctional interfacial modification in the organic solar cells due to well-defined nanoribbons containing CNTs with continuously onedimensional length and promoting the charge transporting, different from the GONR unzipped from single-walled carbon nanotubes tending to form large amount of graphene oxide pieces. Incorporation of the GONR/CNTs into the solution processed organic solar cells as ETL and HTL simultaneously delivers a high device performance with long-term stability. The results demonstrate that the multifunctional GONR/CNTs unzipped from MWCNTs would be a promising interfacial materials for solution processed high performance organic solar cells.Moreover, low-work-function PEDOT:PSS modified with polyethylenimine(PEIE) was used as an ETL for organic solar cells to investigate the study of decline the corrison of ITO by PEDOT:PSS.. A thin layer of PEIE film was spin-coated onto the surface on the PEDOT:PSS films, thus substantially changing their charge selectivity from supporting hole transport to supporting electron transport. It was also found that the PEDOT:PSS/PEIE ETL exhibited higher interfacial contact, a more favorable active morphology, and improved charge mobility. By virtue of these beneficial properties, inverted organic solar cells based on low-bandgap semiconducting photoactive layers achieved a notably improved PCE of 7.94%, superior even to the corresponding performance of devices with only a ZnO layer. Surpassing our expectations, compared with the extreme degradation of device stability observed when pure PEDOT:PSS is used, PEIE-modified PEDOT:PSS can considerably suppress device degradation because of the hydrophobic and alkaline nature of PEIE, which not only reduces the hygroscopicity of the PEDOT:PSS but also neutralizes the acidic PEDOT:PSS and thus prevents the corrosion of the ITO cathode. These results demonstrate the potential of PEIE-modified PEDOT:PSS for use as an efficient ETL in commercial printed electronic devices.In order to investigate simple perovskite solar cell structure, HTL-free CH3NH3PbI3/PC61 BM planar heterojunction perovskite solar cells were fabricated with the configuration of ITO/CH3NH3PbI3/PC61BM/Al. The devices present a remarkable PCE of 11.7%(12.5% best) under AM 1.5G 100 mW cm-2 illumination. Moreover, the HTL-free perovskite solar cells on flexible PET substrates are first demonstrated, achieving a power conversion efficiency of 9.7%. The element distribution in the HTLfree perovskite solar cell was further investigated. The results indicated that the PbI2 enriched near the PC61 BM side for chlorobenzene treatment via the fast deposition crystallization method. Without using HTL on the ITO, the device is stable with comparison to that with PEDOT:PSS as HTL. In addition, the fabricating time of the whole procedure from ITO substrate cleaning to device finishing fabrication only cost about 3 hours for our mentioned devices, which is much more rapid than other structure devices containing other transporting layer. The high efficient and stable HTL-free CH3NH3PbI3/PC61 BM planar heterojunction perovskite solar cells with the advantage of saving time and cost provide the potential for commercialization printing electronic devices.In addition, the grain size and the grain boundary is crucial for perovskite film. We find that the grain size of perovskite was enhanced and the grain boundary was filled with sulfonate carbon nanotubes(s-CNTs) during the CH3NH3PbI3 perovskite precursor solution spin-coating process with the incorporation of s-CNTs. The s-CNTs incorporated perovskite solar cells performance remarkably increased from 10.3% to 15.1%(best) compared with pristine CNTs incorporated perovskite solar cell.