Preparation And Improvement Of Flexible/Rigid Dye-Sensitized Solar Cells Based On ZnO Nanorods/Nanosheets

Dye-sensitized solar cells（DSSCs）are widely regarded as a potential device in commercial solar cells due to its advantages in cost,preparation process,working life and low-light working.With continuous research and improvement,DSSCs achieved 14.3%of highest power conversion efficiency（PCE）.However,its PCE is still insufficient compared/by contrast with the highest PCE of other solar cells.Therefore,many reviews on DSSCs have been complished and reported to help readers understand the research status of DSSCs.However,most of them just make a discussion on the single effect factor of DSSCs,ignoring the integrity,internal interrelation and individual differences.It may lead to unbalance between various performance in research and improvement of DSSCs.In order to solve this problem,the comprehensive analysis and discussion on DSSCs has been complished.This provides the possibility for a quick and comprehensive understanding on DSSCs.Moreover,the comprehensive analysis on DSSCs also provides effective guidance for the improvement of ZnO-based DSSCs.In terms of flexible DSSCs（FDSSCs）,FDSSCs based on ZnO nanorods（NRs）and stainless steel meshes（SSM）were prepared,shown PCE of 0.98%and poor long-term stability.In order to improve its performance,TiO₂ buffer layer was coated on the surface of ZnO NRs by economical and simple（NH₄）₂TiF₆ treatment.The results showed that PCE of2.84%was obtained by ZnO FDSSCs which was treated with（NH₄）₂TiF₆ for 6 minutes.Moreover,the reflecting film is used to reduce the loss of sunlight from the photoanode pore,thereby improving the PCE of FDSSCs.In addition,due to the poor mechanical stability of conductive plastic film-based platinum counter electrodes（Pt/PET CE）,SSM-based platinum counter electrodes（Pt/SSM CE）were prepared to replace Pt/PET CE.The PCE of FDSSCs increased to 3.12%after using reflecting film and PT/SSM CE,and maintained 70.4%of the initial PCE after bends of 800 times.Compared with the ZnO FDSSCs without improvement,ZnO FDSSCs with（NH₄）₂TiF₆ treatment,reflecting film and PT/SSM CE exhibited an increase of 212%in PCE and an improvement of 40%in long-term stability,respectively.In the ZnO rigid DSSCs（RDSSCs）with N719 dye and I^-/I₃^-liquid electrolyte,the functionalized multi-walled carbon nanotubes/polyvinylidene fluoride-hexafluoropropylene（FMWCNT/PVDF-HFP,denoted as FP）composite electrolytes with various mass fractions were synthesized for an alternative of the typical liquid electrolyte.The results shown that the0.5wt%-FP composite electrolyte has the ionic conductivity of 4.48×10^-4s/cm.ZnO RDSSCs based on 0.5wt%-FP composite electrolyte achieved PCE of 2.87%.Its efficiency reaches to95%of that of liquid electrolyte-based ZnO RDSSCs（3.01%）.In addition,ZnO RDSSCs were treated by O₃ plasma for different time.The results showed that PCE of 3.68%was obtained by ZnO RDSSCs with 0.5wt%-FP composite electrolyte and O₃ plasma treatment of10min.Moreover,it kept 86.65%of the initial conversion efficiency after 1008h.Compared with the ZnO RDSSCs typical based on liquid electrolyte,ZnO RDSSCs with 0.5wt%-FP composite electrolyte and O₃ plasma treatment achieved a relative increase of 22%in PCE and an improvement of 72%in long-term stability.The PCE and long-term stability of ZnO-based FDSSCs and RDSSCs were significantly enhanced by low-cost,low-process-requirements and easy-to-implement treatments.This research provides guidance for improving performance and reducing cost.In addition,some enhancements and competitive applications are also summarized,which will further promote the research of ZnO-based DSSCs.