9种树叶生物炭作为染料敏化太阳电池对电极的光电性能

Photovoltaic properties of 9 natural leaves derived biochars as counter electrodes for dye-sensitized solar cells

将9种由树叶经单步热解获得的生物炭作为对电极催化材料引入染料敏化太阳电池（DSSC）,并在分析生物炭的组织结构和电化学性能的基础上,着重探讨了引起器件光电性能差异的内在原因。结果表明：9种树叶热解获得的生物炭组装的DSSC的转换效率在1.00%～1.85%之间,其中棕叶最佳,樟树叶和杨树叶其次,三者的转换效率均高于1.3%,随后依次为枫叶、红继木叶、椿树叶、杉树叶和松针,桂叶最低。生物炭的孔隙结构是引起相应器件光电性能各异的主要原因。由于棕叶生物炭具有独特的取向孔隙,能缩短电解质扩散距离以及提升催化活性,因此其器件的转换效率最佳。此外,9种生物炭器件的转换效率均高于石墨器件（0.77%）。更优的光电性能主要归功于生物炭具有的多级孔结构和玻璃态碳骨架。

The biochars derived from nine kinds of leaves by one-step pyrolysis were employed as counter electrodes in dye-sensitized solar cells（DSSCs）. Based on comprehensive analysis on the microstructure, crystal structure and electrochemical properties of biochars, the intrinsic causes to induce the difference of the photovoltaic properties of the biochars based DSSCs were investigated emphatically. The results indicated that the conversion efficiencies of DSSCs consisting of biochars counter electrodes derive from various leaves ranged from 1.00% to 1.85%. Among them, the palm leaf bring about the best efficiency, followed by camphor leaf, poplar leaf, maple leaf, red after-wood leaf, toona leaf, firry leaf and pine needles, and the cassia leaf with the least efficiency. The pore structure of biochars was believed as one of key factors to induce the difference of the photovoltaic properties of the DSSCs. Since the biochar prepared from palm leaf possessed unique oriented pore structure which could shorten the diffusion length of electrolyte and improve the catalytic activities, the DSSC with the best efficiency was obtained. Especially, all the biochars based DSSCs showed higher efficiency than the graphite based device. The efficiency of the graphite based DSSC is 0.77%. The high performance of biochars based DSSCs can be attributed to the favorable characteristics of the biochars, such as hierarchical pore structure and glassy carbon skeleton. The low temperature（120℃） treatment process can be employed to fabricate a low-cost counter electrode for both glass based DSSCs and flexible DSSCs.