Unclogging electron-transporting channels via self-assembly for improving light harvesting and stability of dye-sensitized solar cells

Abstract

Two nitrogen-rich heterocycle donor dyes, NP-2 and NP-3, have been strategically designed and synthesized to construct functionalized self-assembly layers. Through the formation of N⋯H hydrogen bonds between these nitrogen-rich heterocycle donors and 4-tert-butylbenzoic acid (PTBBA), the electron leak points (imine group (N)) may be plugged, thus blocking excited-state electron lateral transferring between the adsorbed dyes and electron leaking from electron-transporting channel into the electrolyte. Furthermore, the huge 3-dimensional sizes of such supramolecule sensitizers can not only suppress dye aggregation, but enhance the photoresponse capacity in visible region. Therefore, the devices based on NP-2@PTBBA and NP-3@PTBBA, which obtained by the cocktail sensitization procedures, can be improved by increasing the open-circuit photovoltage (Voc) without any loss of the short-circuit photocurrent density (Jsc) owing to the synergy effect between self-assembly and co-sensitization. Although the device based on NP-3/PTBBA via the stepwise sensitization procedure delivers lower efficiency, it can remain at 103.14% of the initial efficiency as a result of parallel increase in Jsc and Voc values. Overall, the design principles provide a clear road map of supramolecular dye-sensitized solar cells (SDSSCs) and demonstrate the potential of 1,3,5-triazine-based dyes in solar cells research.