Reissig L, Mori K, Treadwell R, Dalgleish S, Awaga K
Department of Chemistry and Research Centre for Material Sciences, Nagoya Univeristy, Furo-cho, Chikusa-ku, 464-8602 Nagoya, Japan.
Phys Chem Chem Phys. 2016 Mar 7;18(9):6821-30. doi: 10.1039/c6cp00093b. Epub 2016 Feb 15.
The addition of an insulating layer (I) between one of the metal electrodes (M) and the photoactive semiconducting layer (S) in a standard organic MSM solar cell architecture changes the DC photocurrent response into a strong transient signal. Such a device can, in simple terms, be thought of as a charging voltage source (S) in contact with a charging capacitor (I). The magnitude of the photocurrent signal can be strongly enhanced through the intimate contact of the active layer with the insulating layer, if the various pre-polarizations within the device act synergically. In this study, the effect of the built-in potentials within the device on the polarity and magnitude of the photocurrent response is studied using the well-characterized bulk heterojunction blend system of poly(3-hexylthiophenone):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) as the semiconductor layer, and an ionic liquid as the insulating layer. This study shows that the polarity of the response is not simply determined by the energy level difference of the outer electrodes, but through a delicate interplay of all the energy levels in the device. Furthermore, these observations could be reproduced for devices with a solid-state insulator layer, where possible side-effects of the ionic liquid, such as swelling and doping, could be considered absent.
在标准的有机金属-半导体-金属（MSM）太阳能电池结构中，在其中一个金属电极（M）与光活性半导体层（S）之间添加绝缘层（I），会将直流光电流响应转变为强烈的瞬态信号。简单来说，这样一个器件可以被看作是一个与充电电容器（I）相接触的充电电压源（S）。如果器件内的各种预极化协同作用，通过活性层与绝缘层的紧密接触，光电流信号的幅度可以得到显著增强。在本研究中，使用表征良好的聚（3-己基噻吩）：[6,6]-苯基-C61-丁酸甲酯（P3HT:PCBM）体相异质结共混体系作为半导体层，以及离子液体作为绝缘层，研究了器件内的内建电势对光电流响应的极性和幅度的影响。这项研究表明，响应的极性并非简单地由外部电极的能级差决定，而是通过器件中所有能级的微妙相互作用来决定。此外，对于具有固态绝缘层的器件也能重现这些观察结果，在这种情况下，可以认为离子液体可能产生的副作用，如膨胀和掺杂，并不存在。
