The Effects of Improved Photoelectric Properties of PEDOT:PSS by Two-Step Treatments on the Performance of Polymer Solar Cells Based on PTB7-Th:PC₇₁BM

In this paper, we present a smart two-step treated method to simultaneously improve the work function, conductivity, and transmittance of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) ( PEDOT: PSS). With the two-step treated PEDOT: PSS, the short-circuit current density of polymer solar cells (PSCs) based on PTB7-Th:PC71BM increases from 13.41 to 22.10 mA/cm(2), and the power conversion efficiency increases from 7.35% to 9.82% with 33% improvement. The underlying mechanisms on performance improvement of PSCs can be summarized as follows: (1) two-step treated PEDOT: PSS with the improved work function and the conductivity, which contributes significantly to the charge collection of PSCs; and (2) two-step treated PEDOT: PSS with higher transmittance, which is of benefit to the light absorption of the active layer in PSCs.