近日，英国剑桥大学的Samuel D. Stranks及其研究小组与瑞士洛桑联邦理工学院的Michael Grätzel以及瑞典乌普萨拉大学的Anders Hagfeldt等人合作并取得一项新进展。经过不懈努力，他们发现Cu₂O光电极中沿[111]取向的高载流子迁移率。相关研究成果已于2024年4月24日在国际权威学术期刊《自然》上发表。

本文通过对单晶Cu2O薄膜中载流子复合和输运的新概念理解，展示了Cu₂O光电阴极的性能。研究人员利用环境液相外延，成功开发出一种生长具有三个晶体取向的单晶Cu₂O样品的新方法。宽带飞秒瞬态反射光谱测量用于量化各向异性光电特性，通过该测量，研究人员发现载流子沿[111]方向的迁移率比沿其他方向的迁移率高一个数量级。在这些发现的推动下，研究人员开发了一种多晶Cu₂O光电阴极，该阴极具备高度纯净的(111)取向和(111)端面。

这一创新技术不仅操作简单、成本低廉，而且在0.5V电压下能提供高达7mAcm^-2的电流密度，与最先进的电沉积器件相比，性能提升了70%以上。更重要的是，在空气质量1.5G的照明条件下，与可逆氢电极相比，该光电阴极能稳定运行至少120小时。

据悉，太阳能燃料提供了一种很有前途的方法，旨在通过利用阳光来提供可持续的燃料。经过十年的发展，Cu₂O光电阴极能够提供与现有光伏材料的光电电极相当的性能。然而，大量的载流子复合仍然限制了性能的进一步提升。

附：英文原文

Title: High carrier mobility along the [111] orientation in Cu₂O photoelectrodes

Author: Pan, Linfeng, Dai, Linjie, Burton, Oliver J., Chen, Lu, Andrei, Virgil, Zhang, Youcheng, Ren, Dan, Cheng, Jinshui, Wu, Linxiao, Frohna, Kyle, Abfalterer, Anna, Yang, Terry Chien-Jen, Niu, Wenzhe, Xia, Meng, Hofmann, Stephan, Dyson, Paul J., Reisner, Erwin, Sirringhaus, Henning, Luo, Jingshan, Hagfeldt, Anders, Gratzel, Michael, Stranks, Samuel D.

Issue&Volume: 2024-04-24

Abstract: Solar fuels offer a promising approach to provide sustainable fuels by harnessing sunlight. Following a decade of advancement, Cu₂O photocathodes are capable of delivering a performance comparable to that of photoelectrodes with established photovoltaic materials. However, considerable bulk charge carrier recombination that is poorly understood still limits further advances in performance. Here we demonstrate performance of Cu₂O photocathodes beyond the state-of-the-art by exploiting a new conceptual understanding of carrier recombination and transport in single-crystal Cu₂O thin films. Using ambient liquid-phase epitaxy, we present a new method to grow single-crystal Cu₂O samples with three crystal orientations. Broadband femtosecond transient reflection spectroscopy measurements were used to quantify anisotropic optoelectronic properties, through which the carrier mobility along the [111] direction was found to be an order of magnitude higher than those along other orientations. Driven by these findings, we developed a polycrystalline Cu2O photocathode with an extraordinarily pure (111) orientation and (111) terminating facets using a simple and low-cost method, which delivers 7mAcm^-2 current density (more than 70% improvement compared to that of state-of-the-art electrodeposited devices) at 0.5V versus a reversible hydrogen electrode under air mass 1.5G illumination, and stable operation over at least 120h.

DOI: 10.1038/s41586-024-07273-8

Source: https://www.nature.com/articles/s41586-024-07273-8