Application of a multifunctional liquid crystal material in colored PEDOT:PSS/Si heterojunction solar cells†

PEDOT:PSS/Si heterojunction solar cells (HSCs) with a simple preparation process and low production costs have attracted significant attention. The adjustable color and good stability of the 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), was used as an additive and coating to fabricate colored and stable PEDOT:PSS/Si HSCs. The addition of DT to PEDOT:PSS films improved the conductivity of the films and the junction quality of the devices, leading to an enhanced power conversion efficiency (PCE) of 13.24% for the uncolored devices. Based on the addition of DT to PEDOT:PSS films, DT films with different thicknesses were spin-coated onto the top surface of the uncolored devices, fabricating multi-colored devices with higher PCE compared to the control devices. DT coatings could isolate air and absorb ultraviolet (UV) light, enhancing the stability of colored devices in the air and under extreme UV irradiation. In addition, it was found that DT coatings effectively prevented the poor uniformity of PEDOT:PSS films and the 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.