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Reversible Structural Transformation and Enhanced Performance of PEDOT:PSS-Based Hybrid Solar Cells Driven by Light Intensity

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journal contribution
posted on 15.04.2015 by Joseph Palathinkal Thomas, Saurabh Srivastava, Liyan Zhao, Marwa Abd-Ellah, Donald McGillivray, Jung Soo Kang, Md. Anisur Rahman, Nafiseh Moghimi, Nina F. Heinig, Kam Tong Leung
Hybrid solar cells made of poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS) and appropriate amounts of a cosolvent and a fluorosurfactant on planar n-type silicon substrates showed a photoconversion efficiency (PCE) of above 13%. These cells also exhibited stable, reproducible, and high external quantum efficiency (EQE) that was not sensitive to light-bias intensity (LBI). In contrast, solar cells made of pristine PEDOT:PSS showed low PCE and high EQE only under certain measurement conditions. The EQE was found to degrade with increasing LBI. Here we report that the LBI-sensitive variation of EQE of the low-PCE cells is related to a reversible structural transformation from a quinoid to a benzoid structure of PEDOT.