Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA.
Langmuir. 2010 Apr 6;26(7):4839-47. doi: 10.1021/la903618x.
Sensitization of mesoporous nanocrystalline TiO(2) solar cells with quantum confined semiconductor nanocrystals (QDs) has some advantages over organic dyes or inorganic complex sensitizers, yet the reported efficiencies of laboratory devices are not currently competitive with those of dye sensitized cells. Several methods previously utilized to bind CdSe QDs to mesoporous TiO(2) films were investigated using low index faces of both anatase and rutile TiO(2) polytypes as model systems. The in situ ligand exchange method, where 3-mercaptopropionic acid (MPA) covered TiO(2) crystal surfaces are treated with trioctylphosphine (TOP)/trioctylphosphine oxide (TOPO) (TOP/TOPO)-capped CdSe QDs, resulted in very irreproducible and usually low sensitized photocurrents. The ex situ ligand exchange method, whereby MPA-capped QDs are synthesized and directly adsorbed onto bare TiO(2) single crystals, resulted in both reproducible sensitized photocurrents and surface coverages that are verified with atomic force microscopy (AFM). Purification of the nanocrystals and adjustment of the pH of the sensitization solution to >10.2 was found to prevent QD agglomeration and takes advantage of the dual chemical functionality of MPA to directly link the QDs to the TiO(2) surface. The spectral response of the incident photon to current efficiencies of CdSe QDs was directly compared to the commonly used sensitizer cis-di(thiocyanato)-bis(4,4;-dicarboxy-2,2'-bipyridine)ruthenium(II) (N3) on the same single crystals.
介孔纳米晶 TiO2 太阳能电池敏化量子限制半导体纳米晶（QDs）比有机染料或无机络合染料具有一些优势，但目前实验室器件的效率还无法与染料敏化电池相媲美。之前曾使用几种方法将 CdSe QD 结合到介孔 TiO2 薄膜上，本研究以锐钛矿和金红石 TiO2 多型体的低指数面作为模型系统进行了研究。原位配体交换法，即 3-巯基丙酸（MPA）覆盖的 TiO2 晶体表面用三辛基氧磷（TOP）/三辛基氧化磷（TOPO）（TOP/TOPO）封端的 CdSe QD 处理，导致非常不可重复且通常光电流很低。在体外配体交换法中，MPA 封端的 QD 被合成并直接吸附到裸露的 TiO2 单晶上，得到了可重复的敏化光电流和用原子力显微镜（AFM）验证的表面覆盖率。发现纳米晶体的纯化和敏化溶液 pH 值的调节至>10.2 可防止 QD 聚集，并利用 MPA 的双重化学功能将 QD 直接连接到 TiO2 表面。CdSe QD 的入射光子电流效率的光谱响应与相同单晶上常用的敏化剂顺式-二（硫氰根）-双（4,4′-二羧酸-2,2′-联吡啶）钌（II）（N3）进行了直接比较。
