Response to “Comment on ‘Open-circuit voltage dependency on hole-extraction layers in planar heterojunction organic solar cells’” [Appl. Phys. Lett. 100, 266101 (2012)

Abstract

Yow-Jon Lin 1 had commented that our explanation on Voc relationship as a function of leakage current density in our paper 2 is not completely accurate. In this paper, we have not fully described the tendency of Voc increase in relation to reduction of leakage current density. Seeing inset of Fig. 3 at a glance gives the feeling that there is some tendency of Voc increase with reduction of leakage current density. But, we believe that this is not accurate analysis. Inset of Fig. 3 shows that only two or three data points are closer to the slope. A large deviation on the Voc relationship had existed with leakage current density values using our hole extraction layers; and this was our research motivation. Then, we investigated what could be the other parameters showing such tendency. It can be seen in the inset of Fig. 3, TAPC and NPB have high leakage levels as 10 4 mA/cm 2 range, their devices have high Voc values upto 1.1V. As a comparison 2-TNATA has a bit lower leakage level than TAPC and NPB, however, its Voc is about 0.95V. Therefore, these data could not explain the exact relationship between Voc and leakage current levels. Then, it was difficult to say as results showed somewhat deviation from a real diode. So, we analyzed more sensitive parameters to explain Voc variation. Mobility values and HOMO levels of hole extraction layers were revealed as such parameters to explain more accurately about the variation of Voc values rather than leakage current in our devices. Hence, in our paper, we said about the little tendency of VOC increase with reduction of leakage current density. There may have a little contributions to Voc by leakage current levels, our experimental results showed that leakage current cannot be a significant factor to determine the Voc values in our devices. The other parameters such as mobility values and HOMO levels should be given important consideration in determining the Voc of the devices. 1 Y.-J. Lin, Appl. Phys. Lett. 100, 266101 (2012). 2 C. Kulshreshtha, J. W. Choi, J. Kim, W. S. Jeon, M. C. Suh, Y. Park, and J. H. Kwon, Appl. Phys. Lett. 99, 023308 (2011).