三维多孔复合碳层对电极的制备及其光伏性能研究

Fabrication and photovoltaic performance of counter electrode of 3D porous carbon composite

基于TiO_2光阳极、Pt对电极的染料敏化太阳能电池(DSSC)因其优异的光电转换特性受到了广泛的关注,然而Pt昂贵的价格制约了其发展与应用.针对这一问题,本文设计、制备了一种由相对致密且高导电的石墨膜(PC层,底层)及多孔碳纳米颗粒膜(CC层,顶层)构成的低成本、高性能三维多孔复合碳层对电极.基于该CC/PC对电极的DSSC具有优异的光伏性能:在1.5标准太阳光照射下,其填充因子高达65.28%(较Pt对电极高4.1%)、光电转换效率高达5.9%(为Pt对电极的94.2%). CC/PC对电极的优异光伏性能主要归因于其独特的三维多孔导电结构,该结构有极高的比表面积和丰富的催化反应活性位,有利于电子的快速传输及离子的快速转移,在这些因素的协同作用下,其光电转换性能大大改善.

Dye-sensitized solar cell(DSSC) has been widely investigated due to its low cost, simple fabrication process, and excellent photoelectric conversion efficiency. Generally, the DSSC is composed of photoanode, electrolyte and counter electrode. At present, platinum(Pt) film delivers the highest photoelectric conversion efficiency in the available counter electrode materials. However, Pt film is very expensive and prepared by relatively complicated and high-cost magnetron sputtering, which seriously hinders the large-scale applications in DSSC. Therefore, it is of highly academic and engineering significance to develop novel counter electrode materials with low cost and high photoelectric conversion efficiency to replace expensive Pt counter electrode. Previous research shows that carbon-based nanomaterials such as graphene and carbon nanotubes ard promising to be used as highly efficient counter electrode materials. However, the high-cost and complicated fabrication process restrict their practical applications in DSSC. To address such issues, here in this work,we present and fabricate a highly efficient and low-cost three-dimensional porous carbon composite, which is constructed by the relatively dense and conductive graphite film as bottom layer(PC layer), and the porous carbon nanoparticle film as top layer(CC layer). Our fabricated DSSC consists of commercial TiO2photoanode(4 mm × 4 mm), and PC, CC,CC/PC composite, or Pt counter electrode with a size of 8 mm × 8 mm. The results show that under illumination(100mW/cm2) provided by a solar simulator, the short circuit current densities(open circuit voltages) of DSSCs with PC,CC, CC/PC, and Pt counter electrodes are 11.45 mA/cm2(0.72 V), 11.88 m A/cm2(0.73 V), 12.00 mA/cm2(0.75 V),and 13.46 mA/cm2(0.74 V), respectively. The filling factors of DSSCs with PC, CC, and CC/PC are 56.09%, 59.80%,65.28%, and 62.69%, respectively;the photoelectric conversion efficiencies of DSSCs with PC, CC, and CC/PC are4.61%, 5.20%, 5.90%, and 6.26%, respectively. It is noted that compared with CC layer or PC layer counter electrode,the CC/PC counter electrode delivers better photovoltaic performance. Particularly, the filling factor of DSSC with CC/PC(65.28%) is even 4.10% higher than that of DSSC with commercial Pt(62.69%), and the photoelectric conversion efficiency of the CC/PC-based DSSC is as large as 5.90%, which reaches 94.2% of the Pt-based DSSC(6.26%).The excellent performance of DSSC with CC/PC counter electrode is attributed to the unique three-dimensional porous structure, which can not only facilitate the transfer of electrons and ions, but also provide abundant catalytic sites;these synergistic effects greatly enhance the photovoltaic conversion performance of CC/PC-based DSSC.