Hagstrom Anna L, Weon Seunghyun, Choi Wonyong, Kim Jae-Hong
Department of Chemical and Environmental Engineering , Yale University , New Haven , Connecticut 06511 , United States.
Division of Environmental Science and Engineering , Pohang University of Science and Technology (POSTECH) , Pohang 37673 , Republic of Korea.
ACS Appl Mater Interfaces. 2019 Apr 10;11(14):13304-13318. doi: 10.1021/acsami.9b01945. Epub 2019 Apr 1.
Upconversion (UC) of sub-bandgap photons extends the effective light absorption range of photovoltaic and photocatalytic devices, allowing them to reach higher conversion efficiencies. Recent advances in polymer host materials make it possible to translate triplet-triplet annihilation (TTA)-UC, the UC mechanism most suitable for this purpose, to solid films that can be integrated into devices. The promise of these films is currently limited by the narrow light absorption of TTA-UC sensitizer chromophores, but incorporating multiple sensitizers into layered film systems presents a promising strategy for producing UC materials with broadened light absorption. This strategy is herein applied for photocatalytic air purification, demonstrating its use in a real-world application for the first time. We superimpose optimized red-to-blue and green-to-blue UC films within dual-layer systems and develop a new photocatalyst compatible with their fluorescence emission. By integrating the dual-layer UC film systems with films of this photocatalyst, we produce the first devices that use TTA-UC to harness both red and green sub-bandgap photons for hydroxyl radical generation and photocatalytic degradation of gaseous acetaldehyde, a model volatile organic compound (VOC). Under white light-emitting diode excitation, the dual-layer film systems' broadened light absorption enhances their devices' photocatalytic degradation efficiency, enabling them to degrade twice as much acetaldehyde as their single-sensitizer counterparts. We show that as a result of the different absorption profiles of the two sensitizers, the film order significantly impacts UC fluorescence and VOC degradation. By probing the influence of the excitation light source, excitation geometry, and chromophore spectral overlap on the film systems' UC performance, we propose a framework for the design of multilayer TTA-UC film systems suitable for integration with a variety of photovoltaic and photocatalytic devices.
亚带隙光子的上转换（UC）扩展了光伏和光催化器件的有效光吸收范围，使其能够达到更高的转换效率。聚合物主体材料的最新进展使得将三重态-三重态湮灭（TTA）-UC（最适合此目的的UC机制）转化为可集成到器件中的固体薄膜成为可能。目前，这些薄膜的前景受到TTA-UC敏化剂发色团窄光吸收的限制，但将多种敏化剂纳入层状薄膜系统是生产具有拓宽光吸收的UC材料的一种有前景的策略。本文将该策略应用于光催化空气净化，首次展示了其在实际应用中的用途。我们在双层系统中叠加优化的红到蓝和绿到蓝UC薄膜，并开发出一种与其荧光发射兼容的新型光催化剂。通过将双层UC薄膜系统与这种光催化剂的薄膜集成，我们制造出了首批利用TTA-UC来利用红色和绿色亚带隙光子生成羟基自由基并光催化降解气态乙醛（一种典型的挥发性有机化合物（VOC））的器件。在白色发光二极管激发下，双层薄膜系统拓宽的光吸收提高了其器件的光催化降解效率，使其能够降解的乙醛量是其单敏化剂对应物的两倍。我们表明，由于两种敏化剂的吸收谱不同，薄膜顺序对UC荧光和VOC降解有显著影响。通过探究激发光源、激发几何结构和发色团光谱重叠对薄膜系统UC性能的影响，我们提出了一个适合与各种光伏和光催化器件集成的多层TTA-UC薄膜系统设计框架。
