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Side-chain engineering of medium bandgap polymer donors for efficient polymer solar cells
Organic Electronics ( IF 3.2 ) Pub Date : 2019-12-24 , DOI: 10.1016/j.orgel.2019.105603
Fei Pan , Chenkai Sun , Haijun Bin , Indunil Angunawela , Wenbin Lai , Lei Meng , Harald Ade , Yongfang Li

Polymer solar cells (PSCs) have received widespread attentions recently due to the significant innovations of narrow bandgap n-type organic semiconductor (n-OS) acceptors. To obtain efficient PSCs, it is crucial to employ suitable donor/acceptor pair with matched electronic energy levels, complementary absorption spectra, appropriate molecular self-assembly behavior and preferred blend film morphology, which can be achieved by rational molecular structure optimization. Here we develop three D-A copolymer donors J55, J65 and J75 based on identical building blocks of bithienyl-benzodithiophene (BDTT) D-unit and bifluorine substituted benzotriazole A-unit with different flexible side-chains on BDTT unit to regulate the molecular electronic energy levels and molecular aggregation features, for further improving photovoltaic performance of the PSCs. The three D-A copolymers showed similar absorption profiles due to the identical building blocks. In comparison with the alkyl side-chain substituted polymer J55, the polymers J65 and J75 with alkylthio side-chain and alkylsilyl side-chain showed gradually down-shifted highest occupied molecular orbital energy levels (EHOMO) of −5.38 and −5.43 eV, respectively, which is beneficial for obtaining high open-circuit voltage (Voc). The favorable morphology with preferred face-on orientation and stronger integrated intensity of the π-π stacking peak was formed in J75 blend, which contributes to charge transport, thus enhancing the fill factor (FF) and Jsc. The PSC with J75 as donor and ITIC as acceptor exhibits an efficient PCE of 11.07%, with a Voc of 0.94 V, an enhanced Jsc of 16.99 mA cm−2 and a high FF of 69.29%.



中文翻译:

用于高效聚合物太阳能电池的中带隙聚合物供体的侧链工程

由于窄带隙n型有机半导体(n-OS)受体。为了获得有效的PSC,至关重要的是采用具有匹配的电子能级,互补的吸收光谱,适当的分子自组装行为和优选的共混膜形态的合适的供体/受体对,这可以通过合理的分子结构优化来实现。在此,我们基于相同的联苯基-苯并二噻吩(BDTT)D单元和双氟取代的苯并三唑A-单元(在BDTT单元上具有不同的柔性侧链)开发了三个DA共聚物供体J55,J65和J75,以调节分子电子能级和分子聚集特征,以进一步提高PSC的光伏性能。由于相同的结构单元,这三种DA共聚物显示出相似的吸收曲线。E HOMO)分别为-5.38 eV和-5.43 eV,这对于获得高开路电压(V oc)是有利的。在J75共混物中形成了具有良好的面朝上取向和π-π堆积峰更强积分强度的良好形态,这有助于电荷传输,从而提高了填充因子(FF)和J sc。以J75为供体,ITIC为受体的PSC的有效PCE为11.07%,V oc为0.94 V,增强的J sc为16.99 mA cm -2,高FF为69.29%。

更新日期:2019-12-25
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