Department of Chemistry and ‡Department of Physics, Colorado State University , Fort Collins, Colorado 80523, United States.
ACS Appl Mater Interfaces. 2016 Feb;8(7):4911-7. doi: 10.1021/acsami.5b11037. Epub 2016 Feb 9.
Poor charge transport in Cu2ZnSnS4 (CZTS) nanocrystal (NC) thin films presents a great challenge in the fabrication of solar cells without postannealing treatments. We introduce a novel approach to facilitate the charge carrier hopping between CZTS NCs by growing a stoichiometric Cu2Se shell that can be oxidized to form a conductive Cu2-xSe phase when exposed to air. The CZTS/Cu2Se core/shell NCs with varying numbers of shell monolayers were synthesized by the successive ionic layer adsorption and reaction (SILAR) method, and the variation in structural and optical properties of the CZTS NCs with varying shell thicknesses was investigated. Solid-phase sulfide ligand exchange was employed to fabricate NC thin films by layer-by-layer dip coating and a 2 orders of magnitude rise in dark conductivity (∼10(-3) S cm(-1) at 0 monolayer and ∼10(-1) S cm(-1) at 1.5 monolayers) was observed with an increase in the number of shell monolayers. The approach described herein is the first key step in achieving a significant increase in the photoconductivity of as-deposited CZTS NC thin films.
在不进行后退火处理的情况下，Cu2ZnSnS4 (CZTS) 纳米晶体 (NC) 薄膜中电荷输运性能差，这给太阳能电池的制造带来了巨大的挑战。我们引入了一种新方法，通过生长化学计量比的 Cu2Se 壳来促进 CZTS NC 之间的电荷载流子跳跃，当暴露于空气中时，Cu2Se 壳可以被氧化形成导电的 Cu2-xSe 相。通过连续离子层吸附和反应 (SILAR) 法合成了具有不同壳层数的 CZTS/Cu2Se 核/壳 NC，研究了不同壳厚度下 CZTS NC 的结构和光学性质的变化。采用固相硫代配体交换法通过层层浸涂法制备 NC 薄膜，并观察到随着壳层数的增加，暗电导率提高了 2 个数量级（在 0 单层时约为 10(-3) S cm(-1)，在 1.5 单层时约为 10(-1) S cm(-1)）。本文所述的方法是实现沉积 CZTS NC 薄膜光电导显著提高的关键步骤之一。
