Influence of Phase Segregation on Recombination Dynamics in Organic Bulk-Heterojunction Solar Cells
Influence of Phase Segregation on Recombination Dynamics in Organic Bulk-Heterojunction Solar Cells
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DOI：
10.1002/adfm.201002358
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发表时间：
2011-05-10
影响因子：
19
通讯作者：
Deibel, Carsten
中科院分区：
文献类型：
--
作者：
Baumann, Andreas;Savenije, Tom J.;Deibel, Carsten
研究了以供体-受体比例分别为1:1和1:4的聚(2,5-二（3-十二烷基噻吩-2-基）噻吩[2,3-b]噻吩（pBTCT-C-12）：[6,6]-苯基- c -61-丁酸甲酯（pc61bm）共混体系制备的有机体积异质结（BHJ）太阳能电池中载流子的重组动力学。采用线性增压提取载流子技术（光- celiv）和时间分辨微波电导率作为局部探针技术。在photoceliv实验中，两种混合物在最初提取的电荷载流子浓度之间存在一个数量级的差异，这可以归因于1:1 pBTCTC(12):PC61 BM BHJ太阳能电池中通过具有隔离相区的精细互穿网络产生的增强的双相重组。相反，在1:4混合器件中，广泛的相分离导致极化子的高效产生，从而导致太阳能电池的短路电流密度增加。利用互补实验发现，两种比例的极化子都存在双分子重组。在低于300k的温度下，以上两个载流子的衰变顺序可以用捕获电荷的释放来解释。这种机制导致延迟的双分子重组过程。实验结果可以推广到所有允许相分离的聚合物：富勒烯共混体系。
The recombination dynamics of charge carriers in organic bulk-heterojunction (BHJ) solar cells made of the blend system poly(2,5-bis(3-dodecylthiophen-2-yl) thieno[2,3-b] thiophene) (pBTCT-C-12):[6,6]-phenyl-C-61-butyric acid methyl ester (PC 61 BM) with a donor-acceptor ratio of 1:1 and 1:4 are studied here. The techniques of charge-carrier extraction by linearly increasing voltage (photo-CELIV) and, as local probe, time-resolved microwave conductivity are used. A difference of one order of magnitude is observed between the two blends in the initially extracted charge-carrier concentration in the photo-CELIV experiment, which can be assigned to an enhanced geminate recombination that arises through a fi ne interpenetrating network with isolated phase regions in the 1:1 pBTCTC(12):PC61 BM BHJ solar cells. In contrast, extensive phase segregation in 1:4 blend devices leads to an efficient polaron generation that results in an increased shortcircuit current density of the solar cells. For both studied ratios a bimolecular recombination of polarons is found using the complementary experiments. The charge-carrier decay order of above two for temperatures below 300 K can be explained on the basis of a release of trapped charges. This mechanism leads to delayed bimolecular recombination processes. The experimental fi ndings can be generalized to all polymer:fullerene blend systems allowing for phase segregation.