Korea Center for Artificial Photosynthesis, Center for Nano Materials, Department of Chemistry, Sogang University, Seoul 121-742, Korea.
Langmuir. 2011 Dec 6;27(23):14678-88. doi: 10.1021/la2025395. Epub 2011 Nov 3.
Zeolite Y films (0.35-2.5 μm), into which CdS and PbS quantum dots (QDs) were loaded, were grown on ITO glass. The CdS QD-loaded zeolite Y films showed a photovoltaic effect in the electrolyte solution consisting of Na(2)S (1 M) and NaOH (0.1 M) with Pt-coated F-doped tin oxide glass as the counter electrode. In contrast, the PbS QD-loaded zeolite Y films exhibited a negligible PV effect. This contrasting behavior was proposed to arise from the large difference in driving force for the electron transfer from S(2-) in the solution to the hole in the valence band of QDs, with the former being much larger (2 eV) than the latter (1 eV). In the case of CdS QD-loaded zeolite Y with a loaded amount of CdS of 6.3 per unit cell, the short circuit current, open circuit voltage, fill factor, and efficiency were 0.3 mA cm(-2), 423 V, 28, and 0.1%, respectively, under the AM 1.5, 100 mW cm(-2) condition. This cell was stable for more than 18 days of continuous measurements. A large (3-fold) increase in overall efficiency was observed when PbS QD-loaded zeolite Y on ITO glass was used as the counter electrode. This phenomenon suggests that the uphill electron transfer from ITO glass to S in the solution is facilitated by the photoassisted pumping of the potential energy of the electron in ITO glass to the level that is higher than the reduction potential of S by PbS QDs. Under this condition, the incident-photon-to-current conversion efficiency (IPCE) value at 398 nm was 42% and the absorbed-photon-to-current conversion efficiency (APCE) value at 405 nm was 82%. The electrolyte-mediated interdot charge transport within zeolite films is concluded to be responsible for the overall current flow.
负载 CdS 和 PbS 量子点 (QD) 的沸石 Y 薄膜（0.35-2.5 μm）生长在 ITO 玻璃上。CdS QD 负载的沸石 Y 薄膜在由 Na(2)S（1 M）和 NaOH（0.1 M）组成的电解质溶液中表现出光伏效应，而 Pt 涂覆的 F 掺杂氧化锡玻璃作为对电极。相比之下，PbS QD 负载的沸石 Y 薄膜表现出可忽略不计的 PV 效应。这种对比行为被认为源于从溶液中的 S(2-)到 QD 价带中的空穴的电子转移的驱动力的巨大差异，前者比后者大得多（2 eV）（1 eV）。在 CdS QD 负载的沸石 Y 中，当负载量为每个单元 6.3 个 CdS 时，在 AM 1.5、100 mW cm(-2)条件下，短路电流、开路电压、填充因子和效率分别为 0.3 mA cm(-2)、423 V、28 和 0.1%。该电池在连续测量 18 天以上仍保持稳定。当 ITO 玻璃上负载 PbS QD 的沸石 Y 用作对电极时，整体效率提高了 3 倍。这一现象表明，从 ITO 玻璃到溶液中的 S 的上坡电子转移是由光辅助将 ITO 玻璃中电子的势能泵送到高于 PbS QD 还原 S 的还原电位的水平来促进的。在这种情况下，398nm 的入射光子到电流转换效率（IPCE）值为 42%，405nm 的吸收光子到电流转换效率（APCE）值为 82%。结论是沸石薄膜内的电解质介导的点间电荷输运负责整体电流流动。
