Understanding morphology effects on fill factor losses in dilute-donor organic solar cells
Understanding morphology effects on fill factor losses in dilute-donor organic solar cells
复制标题
了解形态对稀供体有机太阳能电池填充因子损失的影响
DOI：
10.1016/j.nanoen.2022.107793
复制
发表时间：
2022
期刊：
影响因子：
17.6
通讯作者：
Vandenberghe, William G.
中科院分区：
文献类型：
--
作者：
Kramer, Aaron;Kaiser, Waldemar;Zhang, Boya;Murthy, Lakshmi N.S.;Gagliardi, Alessio;Hsu, Julia W.P.;Vandenberghe, William G.
与具有聚合物供体的稀释供体太阳能电池（DDSC）相比，使用小分子供体的具有低供体浓度的有机太阳能电池的实验结果显示出显著更低的填充因子（FF）。我们进行实验和动力学Monte Carlo模拟，以了解所观察到的FF差异以及如何改进FF。我们的研究结果表明，小分子DDSC收集从附近的阳极，而聚合物DDSC收集从更深的体积内的活性层的区域的空穴的活性层。从阳极延伸到活性层中的聚合物链的形态促进了这种扩大的收集区域。这些链允许空穴沿着施主位置跳跃到阳极，没有势垒。相比之下，小分子DDSC需要大的电场来将空穴从隔离的供体位点转移回到受体基质以到达阳极。因此，小分子DDSC中的收集受限于阳极附近供体上的光生空穴。我们提出的策略，以增加DDSC FF的水平相媲美的本体异质结有机太阳能电池，通过减少供体-受体最高占据分子轨道能量偏移，或通过工程的活性层形态，使更高密度的供体接近/接触阳极。
Experimental results of organic solar cells with low donor concentrations using small molecule donors have displayed significantly lower fill factors (FFs) compared to dilute-donor solar cells (DDSCs) with polymer donors. We perform experiments and kinetic Monte Carlo simulations, to understand the observed FF discrepancy and how FF can be improved. Our results reveal that small molecule DDSCs collect holes from the region of the active layer near the anode whereas polymer DDSCs collect holes from a deeper volume inside the active layer. This enlarged collection region is facilitated by the morphology of polymer chains extending from the anode into the active layer. The chains permit holes to hop along the donor sites to the anode with no barrier. Small molecule DDSCs, in contrast, require a large electric field to transfer holes from isolated donor sites back to the acceptor matrix to reach the anode. Collections in small molecule DDSCs are thus constrained to photogenerated holes on donors near the anode. We propose strategies to increase DDSC FF to levels comparable to bulk-heterojunction organic solar cells by decreasing the donor-acceptor highest occupied molecular orbital energy offset, or by engineering the active layer morphology so that a higher density of donors are in proximity/contact with the anode.