Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA.
Nat Commun. 2012;3:1043. doi: 10.1038/ncomms2057.
Recently, much effort has been devoted to improve the efficiency of organic photovoltaic solar cells based on blends of donors and acceptors molecules in bulk heterojunction architecture. One of the major losses in organic photovoltaic devices has been recombination of polaron pairs at the donor-acceptor domain interfaces. Here, we present a novel method to suppress polaron pair recombination at the donor-acceptor domain interfaces and thus improve the organic photovoltaic solar cell efficiency, by doping the device active layer with spin 1/2 radical galvinoxyl. At an optimal doping level of 3 wt%, the efficiency of a standard poly(3-hexylthiophene)/1-(3-(methoxycarbonyl)propyl)-1-1-phenyl)(6,6)C(61) solar cell improves by 18%. A spin-flip mechanism is proposed and supported by magneto-photocurrent measurements, as well as by density functional theory calculations in which polaron pair recombination rate is suppressed by resonant exchange interaction between the spin 1/2 radicals and charged acceptors, which convert the polaron pair spin state from singlet to triplet.
最近，人们致力于提高基于本体异质结结构的给体和受体分子混合物的有机光伏太阳能电池的效率。有机光伏器件的主要损耗之一是在给体-受体域界面处极化子对的复合。在这里，我们提出了一种通过在器件活性层中掺杂自旋 1/2 自由基半醌来抑制给体-受体域界面处极化子对复合，从而提高有机光伏太阳能电池效率的新方法。在最佳掺杂浓度为 3wt%时，标准聚(3-己基噻吩)/1-(3-(甲氧基羰基)丙基)-1-1-苯基)(6,6)C(61)太阳能电池的效率提高了 18%。提出了一种自旋翻转机制，并通过磁光电流测量以及密度泛函理论计算得到了支持，其中自旋 1/2 自由基和带电受体之间的共振交换相互作用抑制了极化子对复合速率，从而将极化子对的自旋态从单态转换为三重态。
