Morphological and electrical control of fullerene dimerization determines organic photovoltaic stability
Morphological and electrical control of fullerene dimerization determines organic photovoltaic stability
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DOI：
10.1039/c5ee02912k
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发表时间：
2016-01-01
影响因子：
32.5
通讯作者：
Brabec, Christoph J.
中科院分区：
文献类型：
--
作者：
Heumueller, Thomas;Mateker, William R.;Brabec, Christoph J.
富勒烯二聚化与由某些聚合物-富勒烯系统组成的有机太阳能电池中的短路电流（J（sc））损失有关。我们调查了几个聚合物富勒烯系统，目前J（SC）损失到不同程度，以确定在何种条件下发生二聚。通过将二聚体重新引入到新的器件中，我们证实了光诱导的二聚体确实是J（SC）损失的起源。我们发现，薄膜的形态和电偏压影响的光二聚化过程，从而相关的J（SC）的损失。在普通富勒烯膜中，较高的结晶度可以抑制二聚反应，如通过高效液相色谱（HPLC）测量所观察到的。在共混膜中，二聚的量取决于聚合物和富勒烯之间的混合程度。对于具有非常无定形的聚合物的高度混合的系统，没有观察到二聚化。在具有纯聚合物和富勒烯域的太阳能电池中，我们通过热退火将富勒烯形态从非晶调整为结晶。类似于纯富勒烯薄膜，我们观察到改善的光稳定性与结晶富勒烯域的设备。将所研究的太阳能电池的操作条件从V-oc改变为J（sc）也显著降低了与二聚化相关的J（sc）损失的量;活性层的HPLC分析表明，如果电池保持在V-oc而不是J（sc），则形成更多的二聚体。偏压对二聚化的影响，以及PL淬灭和减少二聚化之间的明确相关性后，加入少量的无定形聚合物到PC60 BM膜，表明通过激子的反应机制。
Fullerene dimerization has been linked to short circuit current (J(sc)) losses in organic solar cells comprised of certain polymer-fullerene systems. We investigate several polymer-fullerene systems, which present J(sc) loss to varying degrees, in order to determine under which conditions dimerization occurs. By reintroducing dimers into fresh devices, we confirm that the photo-induced dimers are indeed the origin of the J(sc) loss. We find that both film morphology and electrical bias affect the photodimerization process and thus the associated loss of J(sc). In plain fullerene films, a higher degree of crystallinity can inhibit the dimerization reaction, as observed by high performance liquid chromatography (HPLC) measurements. In blend films, the amount of dimerization depends on the degree of mixing between polymer and fullerene. For highly mixed systems with very amorphous polymers, no dimerization is observed. In solar cells with pure polymer and fullerene domains, we tune the fullerene morphology from amorphous to crystalline by thermal annealing. Similar to neat fullerene films, we observe improved light stability for devices with crystalline fullerene domains. Changing the operating conditions of the investigated solar cells from V-oc to J(sc) also significantly reduces the amount of dimerization-related J(sc) loss; HPLC analysis of the active layer shows that more dimers are formed if the cell is held at V-oc instead of J(sc). The effect of bias on dimerization, as well as a clear correlation between PL quenching and reduced dimerization upon addition of small amounts of an amorphous polymer into PC60BM films, suggests a reaction mechanism via excitons.