【摘要】 a-Si:H薄膜中存在的无序结构和缺陷会大幅减小载流子扩散长度.因此,传统的二维平面叠层光伏器件需要在有效的载流子收集(较短的载流子分离距离)和足够的光吸收(较厚的光吸收层厚度)之间平衡.三维a-Si:H径向结薄膜光伏器件可以很好地解决传统平面结中这一难题,它是直接在气-液-固法生长的竖直站立的硅纳米线框架上构建.三维硅米线框架具有很强的光捕获能力,允许使用十分薄的光吸收层(<100 nm),有助于解除光学吸收长度与电学载流子收集路径之间的耦合.薄的吸收层有助于改善光致衰减,提升对材料质量的容忍程度,降低对高品质、成本贵的材料的需求.本文提出了将先进的叠层设计与独特的三维硅纳米线框架相结合的新策略,设计了具有高开启电位的光电阴极,以推动太阳能制氢的应用进程.提出了径向结叠层薄膜光电阴极,其直接在气-液-固法生长的硅纳米线上构筑,由两个径向堆叠的p-i-n结组成.外层p-i-n结的吸收层为非晶硅,用于吸收短波长的光;内层p-i-n结的吸收层则为非晶硅锗合金,用于吸收长波长的光.随机分布的硅纳米线框架具有优异的陷光效应,可允许使用非常薄的非晶硅(～50 nm)和非晶硅锗(～40 nm)吸收层.在100 m W/cm~2的太阳光照射下,该径向结叠层光阴极在覆盖2.5 nm厚的Pt催化剂后,在0.1 mol/L磷酸钾水溶液(KPi, p H=7)电解液中具有1.15 Vvs.RHE的高开启电位,零偏压下的光电流为2.98 m A/cm~2,外加偏压下的光电转换效率为1.72%.综上,本文展现了三维径向结叠层技术的独特潜力,有利于发展下一代高开启电位、高效、低成本、耐用、可大规模制备的光阴极.更多还原

【Abstract】 Combining a progressive tandem junction design with a unique Si nanowire(Si NW) framework paves the way for the development of high-onset-potential photocathodes and enhancement of solar hydrogen production. Herein, a radial tandem junction(RTJ) thin film water-splitting photocathode has been demonstrated experimentally for the first time. The photocathode is directly fabricated on vapor-liquid-solid-grown Si NWs and consists of two radially stacked p-i-n junctions, featuring hydrogenated amorphous silicon(a-Si:H) as the outer absorber layer, which absorbs short wavelengths, and hydrogenated amorphous silicon germanium(a-Si Ge:H) as the inner layer, which absorbs long wavelengths. The randomly distributed Si NW framework enables highly efficient light-trapping, which facilitates the use of very thin absorber layers of a-Si:H(～50 nm) and a-Si Ge:H(～40 nm). In a neutral electrolyte(p H = 7), the three-dimensional(3 D) RTJ photocathode delivers a high photocurrent onset of 1.15 V vs. the reversible hydrogen electrode(RHE), accompanied by a photocurrent of 2.98 m A/cm~2 at 0 V vs. RHE, and an overall applied-bias photon-to-current efficiency of 1.72%. These results emphasize the promising role of 3 D radial tandem technology in developing a new generation of durable, low-cost, high-onset-potential photocathodes capable of large-scale implementation.更多还原