A Study On Laser Selectively Sintering Working Electrode For Flexible DSSCs

Dye sensitized solar cells（DSSCs） have been intensively studied all over the worldduring the last decade due to its low cost,easy to fabricate,and wide applications prospects.The flexible DSSCs show so many advantages such as light weight, good flexibility,andimpact resistance, continuous production by a roll-roll, rapid coating technology, largearea production etc. which reduce production costs. But the flexible conductive substratecould not afford a high temperature treatment, which leads to a low photoelectricconversion efficiency because TiO₂nanocrystalline porous film electrode can not besintered. In this paper, we use laser to selectively sinter TiO₂nanocrystalline porous filmof the flexible photoanode in order to improve the flexible DSSCs Photoelectricconversion efficiency, which is a method of easy operation and fast facture as well asindustrialization continuous production.The effects of the different wavelengths of laser on the absorption, transmission andreflection of flexible substrate, the mechanism of ITO and TiO₂film have beeninvestigated respectively by using the laser selectively sintering technology. We studiedthe effects of the laser sintering parameters such as laser energy density, the scanningspeed,the defocus and overlap,processing methods on the photoelectric conversionefficiency of the flexible optical anode. Finaly, a group of optimized process parameterswas achieved by experiments. Transmittance and surface resistance, morphology, cellphotovoltaic performance testing, transient photocurrent/photovoltage spectroscopycharacterization techniques were used to analyzed and discussed the mechanism of laserselectively sintering flexible photoanode.The experimental results and analysis show:1064nm laser could be used to sinter theTiO₂nanoporous photoanode with flexible PEN substrate, UV355nm laser could beused to sinter TiO₂nanoporous photoanode with flexible PET substrate. After1064nm laser selectively sintering flexible PEN TiO₂working photoanode, the entire fimethickness of the anode became more uniform and compact, which increased the diffusioncoefficient of electrons Dn, reduced load transfer resistance, so that the photoelectricconversion efficiency was improved into3.84%,which is32%higher than the original. For355UV laser selectively sintering flexible PET TiO₂working anode, the effect of lasersintering from photoanode back is better than that from front.After laser sintered flexiblephotoanode, the connection between TiO₂nonaparticles and between TiO₂nonaparticlesand conductive film ITO were changed from the physical contact into neck-typechemical connection, thereby the short-circuit current density of the cells wasenhanced,and the efficiency of the cell photovoltaic was improved into2%,which is twicethat of the original.