A study of TiO2 particle deposition via Laser-assisted NPDS (Nano Particle Deposition System) for the application of flexible DSSC (Dye-Sensitized Solar Cell)

Abstract

레이저 이용 나노 입자 적층 시스템 (Laser assisted nano particle deposition system, La-NPDS)을 이용하여 염료감응형 태양전지(Dye-sensitized solar cell)의 광전극을 제작하고 그 특성을 분석했다. La-NPDS는 노즐을 통해 초음속으로 가속된 분말이 운동에너지에 의해 기판에 적층이 이루어지는 시스템이다. 또한, 분말 적층과 동시에 이루어지는 레이저 처리로 인해 기존의 고온 열처리를 대체할 수 있다는 장점을 가진다. 따라서, 액상 용매가 포함된 Paste 제조가 요구되는 스크린 프린팅이나 닥터 블레이드와 같은 기존 방식을 대체할 수 있다. La-NPDS에 의해 15 nm 크기의 TiO2 입자가 ITO-PET 기판 위에 균일하게 적층이 이루어졌다. 형성된 TiO2의 패턴 두께는 염료감응형 태양전지의 광전극 두께로써 적합한 10.55 μm 로 측정되었다. 레이저 처리된 DSSC의 효율은 1.92 %로, 레이저 처리하지 않은 DSSC의 효율인 1.05 %에 비해 비교적 높은 수치를 보였다. 또한, 레이저 처리 시 형성되는 TiO2 입자들간의 네킹으로 인해 전류 밀도와 fill factor가 상승했다. 본 연구에서는 레이저 처리의 효과를 확인하기 위해 구조적인 분석을 실시했다. 레이저 처리 시 입자들간의 네킹으로 인해 비표면적이 줄었으며, 직렬 저항이 감소했다. 또한, 레이저 처리한 샘플의 염료흡착량이 처리하지 않은 샘플보다 증가함을 확인할 수 있었다. 이러한 결과를 통해 La-NPDS를 통한 TiO2 광전극 형성의 가능성을 확인할 수 있었다. La-NPDS를 통해 제작된 DSSC의 최대 전력에 가까운 실제 활용 전력을 도출하기 위해 Power management unit (PMU) 시스템을 도입하였다. 기본적인 PMU 시스템의 전력을 충족시키기 위해 제작된 DSSC 샘플 세 개를 직렬로 연결하여 모듈로 구성했다. PMU를 적용했을 때의 모듈의 Operating voltage (VPV)가 PMU 시스템을 적용하지 않았을 때보다 2배 정도로 안정되었음을 확인할 수 있었다. 또한, 빛의 세기의 변화에도 안정적으로 VPV가 유지되었다. 이를 통해 La-NPDS로 제작된 유연 DSSC의 에너지 활용 가능성을 확인할 수 있었다. |Unique way of fabricating flexible and translucent dye-sensitized solar cell (DSSC) was demonstrated by forming TiO2 layer for photo-electrode via laser assisted nano particle deposition system (La-NPDS). La-NPDS is a system where powders are accelerated through the nozzle with supersonic velocity to be deposited on the substrate by kinetic energy while laser sintering step was applied to replace its heat treatment. Therefore, this method of deposition can replace conventional fabrication method of photo-electrode which is screen printing and doctor-blade. 15 nm-sized TiO2 particles were uniformly deposited onto indium tin oxide-polyethylene terephthalate (ITO-PET) via La-NPDS for fabrication of DSSC. Thickness of TiO2 pattern was approximately 10.55 μm, which is a proper thickness for photo-electrode of DSSC. Laser sintered DSSC was found to have better efficiency compared to that of no laser treated sample. Efficiency of laser treated sample was measured to be 1.92%, which is higher than the efficiency of the sample without laser treatment (1.05%). Moreover, short circuit current density and fill factor of DSSC with laser treatment dramatically increased due to improvement in necking among adjacent particles. Further, structural properties of laser sintering have been studied. It was found that the surface area of the laser treated sample decreased due to particle necking, resulting in decrease of the series resistance. Amount of dye absorption of the sample with laser treatment was found to be three times larger than that of the sample without laser treatment. Therefore, the possibility of forming TiO2 layer for photo-electrode via La-NPDS was successfully demonstrated. Finally, power management unit (PMU) system has been introduced to induce the higher operating point close to maximum power of flexible DSSC fabricated via La-NPDS. Flexible DSSCs were connected in series as a module to satisfy the power requirements of PMU system. The measured operating voltage (VPV) from module with PMU moved to the maximum power point of the module. Moreover, the Vpv from flexible DSSCs module with PMU system was proven to be more stable than that from flexible DSSC without PMU system at varying light intensities. Therefore, energy harvesting capability of flexible DSSC fabricated by La-NPDS was successfully demonstrated.; Unique way of fabricating flexible and translucent dye-sensitized solar cell (DSSC) was demonstrated by forming TiO2 layer for photo-electrode via laser assisted nano particle deposition system (La-NPDS). La-NPDS is a system where powders are accelerated through the nozzle with supersonic velocity to be deposited on the substrate by kinetic energy while laser sintering step was applied to replace its heat treatment. Therefore, this method of deposition can replace conventional fabrication method of photo-electrode which is screen printing and doctor-blade. 15 nm-sized TiO2 particles were uniformly deposited onto indium tin oxide-polyethylene terephthalate (ITO-PET) via La-NPDS for fabrication of DSSC. Thickness of TiO2 pattern was approximately 10.55 μm, which is a proper thickness for photo-electrode of DSSC. Laser sintered DSSC was found to have better efficiency compared to that of no laser treated sample. Efficiency of laser treated sample was measured to be 1.92%, which is higher than the efficiency of the sample without laser treatment (1.05%). Moreover, short circuit current density and fill factor of DSSC with laser treatment dramatically increased due to improvement in necking among adjacent particles. Further, structural properties of laser sintering have been studied. It was found that the surface area of the laser treated sample decreased due to particle necking, resulting in decrease of the series resistance. Amount of dye absorption of the sample with laser treatment was found to be three times larger than that of the sample without laser treatment. Therefore, the possibility of forming TiO2 layer for photo-electrode via La-NPDS was successfully demonstrated. Finally, power management unit (PMU) system has been introduced to induce the higher operating point close to maximum power of flexible DSSC fabricated via La-NPDS. Flexible DSSCs were connected in series as a module to satisfy the power requirements of PMU system. The measured operating voltage (VPV) from module with PMU moved to the maximum power point of the module. Moreover, the Vpv from flexible DSSCs module with PMU system was proven to be more stable than that from flexible DSSC without PMU system at varying light intensities. Therefore, energy harvesting capability of flexible DSSC fabricated by La-NPDS was successfully demonstrated.