Application of a Multifunctional Liquid Crystal Material in Colorful PEDOT:PSS/Si Heterojunction Solar Cells

PEDOT:PSS/Si heterojunction solar cells (HSCs) with simple preparation process and low production costs has attracted a lot of attention. The adjustable color and good stability of devices will greatly expand their application scenarios. In this work, a liquid crystal molecule, 5,5'-bis(9-(3,4,5-tris(tetradecyloxy)benzyl)-9H-carbazol-3-yl)-2,2'-bithiophene (DT), is used as the additive and coating to fabricate colored and stable PEDOT:PSS/Si HSCs. The DT as the additive into PEDOT:PSS films can improve the conductivity of films and the junction quality of devices, leading to enhanced power conversion efficiency (PCE) of 13.24% for the uncolored devices. On based of PEDOT:PSS films adding DT, DT films with different thickness as coatings were spin-coated on the top surface of the uncolored devices, fabricating multi-color devices with the higher PCE, compared to the control devices. DT coatings can isolate air and absorb ultraviolet (UV) light, obtaining the enhanced stability for colorful devices in the air and under extreme UV irradiation. In addition, it was found that DT coatings can effectively avoid the poor uniformity of PEDOT:PSS films and disrupted linear structure of PEDOT chains under UV illumination. The work provides promising strategies for the preparation of colored and stable PEDOT:PSS/Si HSCs with high efficiency.