Rana, Aniket and Kumar, Amit and Vashistha, Nikita and Garg, Kuldeep K. and Chand, Suresh and Singh, Rajiv K. (2020) Origin of depressed fill factor in organic solar cells due to S-shape current-voltage characteristics. Journal of Applied Physics , 127 (5). 053101-053108. ISSN 0021-8979

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Often, a depressed fill factor is observed in organic solar cells (OSCs), which is usually known as S-shaped current-voltage (J-V) characteristics. To investigate the origin of the depressed fill factor further, a poly[N-9-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2,1,3-benzothiadiazole)]:[6,6]-phenyl C71 butyric acid methyl ester based OSC has been characterized through impedance spectroscopy. In addition, the photocurrent vs the applied effective bias plot reveals that the S-shaped J-V characteristics primarily reduce the diffusion current of the device. The present study shows that the diffusion current dominated section of photocurrent reduces with a slope of 2 in the depressed fill factor section given that the slope may further increase as per the impact of the S-shape. The reduction in the diffusion constant (D-n) in the S-shaped region supports the decrease in the diffusion current, which is observed through the photocurrent analysis. It is observed that, in the S-shaped section of the current-voltage characteristics, the transport time for free carriers increases up to 443 mu s. The larger Urbach energy for the active layer of an S-shaped device demonstrates higher subbandgap disorder. Therefore, it is concluded that the accumulation of the charge carriers within the device and disorder in the active layer leads to the S-shaped current-voltage characteristics as well as poor carrier extraction.

Item Type: Article
Additional Information: Copyright for this article belongs to M/s American Institute of Physics.
Subjects: Applied Physics/Condensed Matter
Depositing User: Mr. Yogesh Joshi
Date Deposited: 08 Apr 2022 06:07
Last Modified: 08 Apr 2022 06:07
URI: http://npl.csircentral.net/id/eprint/4840

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