Relating Recombination, Density of States, and Device Performance in an Efficient Polymer: Fullerene Organic Solar Cell Blend
Relating Recombination, Density of States, and Device Performance in an Efficient Polymer: Fullerene Organic Solar Cell Blend
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DOI：
10.1002/aenm.201300194
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发表时间：
2013-09-01
影响因子：
27.8
通讯作者：
Durrant, James R.
中科院分区：
文献类型：
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作者：
Hawks, Steven A.;Deledalle, Florent;Durrant, James R.
我们探索了高效聚[4,8-二-（2-乙基己氧基）-苯并[1,2-b:4,5-b']二噻吩-2,6-二基-4-（2-乙基己氧基-1- 1）噻吩[3,4-b]噻吩-2,6-二基]:[6,6]-苯基- c -71-丁酸甲酯（PBDTTT-C:PC71BM）块状异质结有机太阳能电池的态密度、重组动力学和器件性能之间的相互关系。我们通过在一个小范围内改变聚合物：富勒烯组成来调节活性层的状态密度，该比例可以导致最大的太阳能电池效率（50-67 wt% PC71BM）。利用瞬态和稳态技术，我们发现非共轭复合限制了器件效率，此外，增加PC71BM含量同时增加了载流子寿命和漂移迁移率，这与Langevin复合的预期行为相反。随着富勒烯含量的增加，电子性质的变化伴随着局域态密度的大小或能量分离的显著变化。我们理解器件性能的综合方法在理解限制这些高效聚合物：富勒烯体系的因素方面取得了重大进展。
We explore the interrelation between density of states, recombination kinetics, and device performance in efficient poly[4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-4-(2-ethylhexyloxy-1-one)thieno[3,4-b]thiophene-2,6-diyl]:[6,6]-phenyl-C-71-butyric acid methyl ester (PBDTTT-C:PC71BM) bulk-heterojunction organic solar cells. We modulate the active-layer density of states by varying the polymer:fullerene composition over a small range around the ratio that leads to the maximum solar cell efficiency (50-67 wt% PC71BM). Using transient and steady-state techniques, we find that nongeminate recombination limits the device efficiency and, moreover, that increasing the PC71BM content simultaneously increases the carrier lifetime and drift mobility in contrast to the behavior expected for Langevin recombination. Changes in electronic properties with fullerene content are accompanied by a significant change in the magnitude or energetic separation of the density of localized states. Our comprehensive approach to understanding device performance represents significant progress in understanding what limits these high-efficiency polymer:fullerene systems.