Magnetoconductance Study on Nongeminate Recombination in Solar Cell Using Poly(3-hexylthiophene) and [6,6]-Phenyl-C61-butyric Acid Methyl Ester
Magnetoconductance Study on Nongeminate Recombination in Solar Cell Using Poly(3-hexylthiophene) and [6,6]-Phenyl-C61-butyric Acid Methyl Ester
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DOI：
10.1021/acsomega.8b01746
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发表时间：
2018-08
期刊：
影响因子：
4.1
通讯作者：
Ryota Shoji;T. Omori;Yusuke Wakikawa;Tomoaki Miura;T. Ikoma
中科院分区：
文献类型：
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作者：
Ryota Shoji;T. Omori;Yusuke Wakikawa;Tomoaki Miura;T. Ikoma
以聚（3 - 己基噻吩）（P3HT）为给体（D）和[6,6] - 苯基 - C61 - 丁酸甲酯（PCBM）为受体（A），对单结（SJ）和体结（BJ）两种类型的有机太阳能电池的磁电导（MC）效应进行了研究。在暗态和光照条件下测量的MC效应的磁场依赖性中，观察到三种半峰全宽（B1/2）分别为4 ± 1、20 ± 15和>400 mT的成分，以下依次称为MCS、M、B。MCS、M、B成分的大小不仅对电池的结结构敏感，而且对入射光的有无也敏感。SJ电池在暗态下MC效应的偏压（V）依赖性在暗电流的开启电压（VON）附近达到最大，此时活性层达到平带条件。SJ电池的MCM成分的B1/2随V超过VON而增加。在光照下，BJ电池表现出MC效应，而SJ电池未检测到效应。光照下BJ电池的MCS、M成分随入射光功率增加。使用纳秒脉冲激光测量的BJ电池的瞬态MCS、M成分随闪光后的延迟时间增加。综合这些现象以及MC效应的相位，可以得出结论：所有MC成分均源于磁场对非孪生电子（e） - 空穴（h）对自旋转换的影响，在D/A界面存在自旋相关的电荷复合。MCS、M、B的B1/2值分别可由超精细相互作用导致的自旋转换、自旋弛豫以及e（PCBM - ）和h（P3HT + ）的g因子差异来解释。对光照下短路条件下观察到的BJ电池的MCS、M成分进行动力学模拟，得出非孪生复合的效率约为40%，同时伴随着三线态激子的产生以及弛豫到基态单重态。适度三线态复合的损耗机制表明通过收集三线态激子来提高功率转换效率具有重要的可能性。
The magnetoconductance (MC) effect was investigated for two types of organic solar cells with single junction (SJ) and bulk junction (BJ) of poly(3-hexylthiophene) (P3HT) as donor (D) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as acceptor (A). Three components with different half-field-at-half-maximums (B1/2) of 4 ± 1, 20 ± 15 and >400 mT, hereafter referred to MCS,M,B in a sequence, were observed in the magnetic field dependence of the MC effects measured under dark and light conditions. The magnitude of the MCS,M,B components is sensitive to not only the junction structure of the cell but also the presence or absence of incident light. The bias voltage (V) dependence of the MC effect in the dark for the SJ-cell is maximized around the turn-on voltage (VON) of the dark current, where a flat band condition of the active layer is achieved. The B1/2 for the MCM component of the SJ-cell increases with V beyond VON. In light, the BJ-cell exhibits the MC effect, whereas no effect is detected for the SJ-cell. The MCS,M components for the BJ-cell in light increase with the incident light power. The transient MCS,M components for the BJ-cell measured using a nanosecond pulse laser increases with the delay time after the flash. By integrating these phenomena and the phase of the MC effect, it is concluded that all of the MC components arise from the magnetic field effect on the spin conversion of nongeminate electron (e)–hole (h) pairs with spin-dependent charge recombinations at the D/A-interface. The B1/2 values for MCS,M,B are, respectively, understood by the spin conversion due to the hyperfine interaction, the spin relaxation, and the g-factor difference for e (PCBM–) and h (P3HT+). Kinetic simulations of the MCS,M components for the BJ-cell observed at the short-circuit condition in light yield an efficiency of ca. 40% for the nongeminate recombination, which is accompanied by the generation of triplet excitons as well as relaxation to a ground singlet state. The loss mechanism of moderate triplet recombination suggests an important possibility to improve the power conversion efficiency by harvesting of the triplet excitons.