Khlyabich Petr P, Rudenko Andrey E, Street Robert A, Thompson Barry C
Department of Chemistry and Loker Hydrocarbon Research Institute, University of Southern California , Los Angeles, California 90089-1661, United States.
ACS Appl Mater Interfaces. 2014 Jul 9;6(13):9913-9. doi: 10.1021/am502122a. Epub 2014 Jun 27.
The evolution of the open-circuit voltage (Voc) with composition in ternary blend bulk heterojunction (BHJ) solar cells is correlated with the miscibility of the polymers. Ternary blends based on poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) and poly(3-hexylthiophene-thiophene-diketopyrrolopyrrole) (P3HTT-DPP-10%) with phenyl-C61-butyric acid methyl ester (PC61BM) acceptor were investigated. The Voc is pinned to the lower value of the P3HTT-DPP-10%:PC61BM binary blend even up to 95% PCDTBT in the polymer fraction. This is in stark contrast to the previously investigated system based on P3HTT-DPP-10%, poly(3-hexylthiophene-co-3-(2-ethylhexyl)thiophene) (P3HT75-co-EHT25), and PC61BM, where the Voc varied regularly across the full composition range, as explained by an organic alloy model, implying strong physical and electronic interaction between the polymers. Photocurrent spectral response (PSR) and external quantum efficiency (EQE) measurements indicate that the present system does not exhibit the hallmarks of alloy formation. Measured values of the surface energies of the polymers support miscibility of P3HTT-DPP-10% with P3HT75-co-EHT25 but not with PCDTBT. Surface energy is proposed as a figure of merit for predicting alloy formation and compositional dependence of the Voc in ternary blend solar cells and miscibility between polymers is proposed as a necessary attribute for polymer pairs that will display alloy behavior.
三元共混体异质结（BHJ）太阳能电池中开路电压（Voc）随组成的变化与聚合物的混溶性相关。研究了基于聚[N-9'-十七烷基-2,7-咔唑-alt-5,5-(4',7'-二-2-噻吩基-2',1',3'-苯并噻二唑)]（PCDTBT）和聚(3-己基噻吩-噻吩-二酮吡咯并吡咯)（P3HTT-DPP-10%）与苯基-C61-丁酸甲酯（PC61BM）受体的三元共混物。即使在聚合物组分中PCDTBT含量高达95%时，Voc仍固定在P3HTT-DPP-10%:PC61BM二元共混物的较低值。这与先前研究的基于P3HTT-DPP-10%、聚(3-己基噻吩-co-3-(2-乙基己基)噻吩)（P3HT75-co-EHT25）和PC61BM的体系形成鲜明对比，在该体系中，Voc在整个组成范围内呈规律变化，如有机合金模型所解释的那样，这意味着聚合物之间存在强烈的物理和电子相互作用。光电流光谱响应（PSR）和外量子效率（EQE）测量表明，当前体系不具有合金形成的特征。聚合物表面能的测量值支持P3HTT-DPP-10%与P3HT75-co-EHT25的混溶性，但不支持与PCDTBT的混溶性。表面能被提议作为预测三元共混太阳能电池中合金形成和Voc组成依赖性的品质因数，聚合物之间的混溶性被提议作为将显示合金行为的聚合物对的必要属性。
