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

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.