期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 142, 期 5, 页码 2562-2571出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.9b12526
关键词
-
资金
- Australian Renewable Energy Agency within the Australian Centre for Advanced Photovoltaics
- Australian Renewable Energy Agency
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences Solar Photochemistry program [DE-SC0015429]
- U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering [DE-SC0012458]
- European Regional Development Fund
- Welsh European Funding Office
- Swansea University strategic initiative in Sustainable Advanced Materials
- National Science Foundation Graduate Research Fellowship [DGE-1656466]
- U.S. Department of Energy (DOE) [DE-SC0015429] Funding Source: U.S. Department of Energy (DOE)
Organic photovoltaic (OPV) efficiencies continue to rise, raising their prospects for solar energy conversion. However, researchers have long considered how to suppress the loss of free carriers by recombination-poor diffusion and significant Coulombic attraction can cause electrons and holes to encounter each other at interfaces close to where they were photogenerated. Using femtosecond transient spectroscopies, we report the nanosecond grow-in of a large transient Stark effect, caused by nanoscale electric fields of similar to 487 kV/cm between photo generated free carriers in the device active layer. We find that particular morphologies of the active layer lead to an energetic cascade for charge carriers, suppressing pathways to recombination, which is similar to 2000 times less than predicted by Langevin theory. This in turn leads to the buildup of electric charge in donor and acceptor domains-away from the interface-resistant to bimolecular recombination. Interestingly, this signal is only experimentally obvious in thick films due to the different scaling of electroabsorption and photoinduced absorption signals in transient absorption spectroscopy. Rather than inhibiting device performance, we show that devices up to 600 nm thick maintain efficiencies of >8% because domains can afford much higher carrier densities. These observations suggest that with particular nanoscale morphologies the bulk heterojunction can go beyond its established role in charge photogeneration and can act as a capacitor, where adjacent free charges are held away from the interface and can be protected from bimolecular recombination.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据