Phase Separation to Improve the Conductivity and Work Function of the PEDOT:PSS Solution for Silicon Hybrid Solar Cells
Qi Geng, Zhe Wang, Zhongliang Gao, Ting Gao, Yingfeng Li, Lei Chen, Meicheng Li
Abstract
Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) is usually used as a hole-selective contact layer in photovoltaic and optoelectronic fields due to its good film-forming property and low cost. However, PSS as a dispersant is an insulating material that restricts the conductivity of PEDOT:PSS films. In this work, we modified the PEDOT:PSS solution by heat treatment to realize the double improvement of the conductivity and work function of the PEDOT:PSS film for PEDOT:PSS/Si hybrid solar cells (HSCs). It was found that phase separation occurs in the process of heat treatment of the PEDOT:PSS solution, which causes the dispersed PEDOT to agglomerate into strips to form a conductive grid. By optimizing the heat treatment temperatures, the electrical conductivity of the PEDOT:PSS film increased from 1090 to 1305 S/cm at 90 °C. In addition, the composition of the PEDOT:PSS solution was changed to increase the value of PEDOT/PSS by 55.12%, which increased the work function of the PEDOT:PSS film from 4.5 to 4.8 eV. After calculation with the finite volume method, the band bending at the Si surface of heterogeneous contact increased by 0.216 eV, which is more conducive to carrier separation. Finally, the power conversion efficiency of the heat-treated PEDOT:PSS solution applied to PEDOT:PSS/Si HSCs increased from 11.03 to 12.38% compared to that of nonheat-treated PEDOT:PSS/Si HSCs.