Design And Preparation Of Flexible Nanopaper-based Solar Cells

As a kind of renewable resource extract,cellulose nanofiber is prepared into nanopaper substrate by interweaving fibers.It has the advantages of flexibility,light weight,high strength and environmentally friendly.It has more excellent material compatibility and special optical properties,which is conducive to reducing the preparation difficulty of devices,improving the utilization of light for devices,and can replace the traditional flexible polymer PET,PEN and other materials which are applied to the preparation of flexible solar cells.However,the research of nanopaper based solar cells is relatively scarce,and there are some difficulties and challenges,which are mainly due to the low preparation efficiency of high-quality cellulose nanofiber,the high dependence of adjustment of the transmittance and haze of nanopaper substrate on materials,and the poor tolerance of nanopaper substrate to aqueous solution,which limit the research and development of nanopaper substrate in the field of flexible solar cells.Based on these advantages and challenges,this paper has studied and achieved the following results:?1?Efficient preparation of cellulose nanofiber by soluble etherification.After carboxymethylation pretreatment with solvent method,the modified fiber was washed with isopropanol to obtain high brittle micro-nano fiber powder with normal size distribution of 49.1?m,which could not only avoid high-pressure homogeneous blocking shutdown,reduce energy consumption to 694?925 k Wh/t,but also obtain 80?90%yield cellulose nanofiber?diameter between 10 and 16 nm?solution.?2?Preparation of controllable optical haze paper substrate.The strength of high transmittance?93%?nanopaper substrate was as high as 107.5 MPa.After the introduction of flocculation principle and physical controlling of the dispersion state of cellulose nanofiber,its transmittance range was expanded to 45?93%,with diffuse reflection capacity increased to225?1332%.After the treatment of epoxy resin,the transmittance was further focused on 80±2%.We also compared nanopaper substrate with epoxy resin enhanced transparent paper substrate,although the strength and transmittance of transparent paper were reduced to 25?35MPa and 10?53%,it still had the ultra-high diffuse reflectance,high definition at small spacing and stronger deformation resistance.?3?Preparation of flexible transparent electrode.A stable low-temperature sintering particle-free silver ink was developed.The silver ink as well as Ag NWs ink were both deposited on the surface of paper substrate respectively.The sintering temperature were controlled to80?120?.A further hot-pressing procedure enhanced the optical and conductivity.The resulting flexible transparent paper electrode with transmittance of 40?80%and square resistance of 10?120?/sq was prepared as well as the opaque paper electrode with resistance below 0.6?/sq.?4?Research and development of flexible paper solar cells.EVA was introduced to fix the paper electrode,with special single-layer or multi-layer structure design and ionic liquid treatment,the V_oc of multi-layer structure organic solar cell was 0.225 V with less than 10%loss after bending.Multi-layer structure lowered the preparing difficulty,but single-layer structure still showed higher efficiency.The efficiency of single-layer structure perovskite solar cells could reach as high as 5.36%.