Metal Nanowire Based Composite Transparent Electrodes and
Semi-transparent Perovskite solar Cells
■ Date: 2017. 03. 29(Wed) , 17:00 ~ 18:15
■ Place: Science BuildingⅠ, Room.202 Multimedia Room
■ Speaker: Prof. Jooho Moon (Yonsei University)
■ Host of a Seminar: Prof. Jang-Sik Lee
※ Speaker Language: KOREAN
Low cost and high efficient photovoltaics have been persistently pursued during the past decade for renewable solar energy conversion. However, the noble metal counter electrodes are typically prepared by thermal evaporation and vacuum sputtered FTO or ITO films are commonly used as a transparent electrode. In this regards, alternative solution method to replace the vacuum processed electrodes is highly demanding to achieve an ultimate goal of the solar cells; inexpensive, high efficient photovoltaic system. Here, we report all-solution-processed transparent conductive electrodes based on Ag nanowire (AgNW)-embedded metal oxide composite films for photovoltaic applications. Transparent electrodes composed of random AgNW networks can be readily achieved by simple and scalable solution processing. However, the AgNWs film is easy to undergo local oxidation and melting on a heated substrate in the atmosphere, which adversely affects the conductivity of the AgNWs film. The metal oxide underlayer acts as an n-type buffer layer as well as a surface flattener against the absorber layer, while the upper layer prevents the AgNWs from local melting-induced disconnection. As a result, the thermal stability of the AgNWs was enhanced and the adhesion of AgNWs to the substrate was improved. Such a composite electrode is also capable of effective charge carrier collection due to filling the empty space unoccupied by AgNWs with metal oxides as well as resulting in a better surface smoothness.
Organic-inorganic hybrid perovskite solar cells have demonstrated huge potential as next generation solar cells with low cost and efficient performances due to solution processability and their excellent photovoltaic characteristics. Several nanostructures such as planar heterojunction, mesoporous metal oxides, or 1-D TiO2 or ZnO nanorod array have been studied to enhance efficiencies of the solar cells. Here, we report semitransparent, highly efficient, one-dimensionally nano-structured perovskite solar cells employing anodized aluminium oxide (AAO) as scaffold layer. The parallel nano-pillars in the perovskite layer enable construction of haze-free semitransparent devices without any hysteresis behavior. By controlling the pore size in the AAO, the volume occupied by the perovskite layer can be precisely varied, and the colour neutrality of the resulting devices can be achieved. With the incorporation of a transparent cathodic electrode (indium tin oxide, ITO) with a buffer layer (MoOx), a highly efficient semitransparent nano-pillared perovskite solar cell is achievable with a power-conversion efficiency of ~10% (7.5%) and a whole device average visible light transmittance of ~30% (38.2%). To determine the role of the scaffold layer in improving the photo-electrical properties of the cell, impedance spectroscopy analyses were performed, revealing that the AAO-structured perovskite layer suppresses internal ion diffusion and enables critical improvements in long-term stability under continuous illumination.
Department of Materials Science and Engineering