Achieving 20% Efficiency for Binary Organic Solar Cells with Suppressed Non-radiative Recombination via Triphenylamine Halides†

Abstract

Minimizing energy loss has been identified as an effective approach to achieve further efficiency breakthroughs in organic solar cells (OSCs), and the main loss channel can be attributed to non-radiative recombination loss (ΔEnr) that is determined by the electroluminescence external quantum efficiency (EQEEL) of the active layer. Despite tremendous efforts in understanding the luminescence properties, ΔEnr remains significantly large. In this work, a series of highly fluorescent triphenylamine halides are used as additives to enhance the luminescence properties of the PM6:L8-BO blends by reducing the static disorder of L8-BO. As a result, the photoluminescence quantum yield (PLQY) of the neat L8-BO film is enhanced from 2.5% to 3.2% upon chlorinated triphenylamine (ClPA) incorporation, and the corresponding EQEEL of the PM6:L8-BO blend is significantly increased from 1.72×10-4 to 2.80×10-4. Moreover, the interactions between ClPA and donor/acceptor molecules promote the formation of an excellent double-fibril network morphology, which facilitates the charge transport and extraction in OSCs. The ClPA-modified PM6:L8-BO and D18:L8-BO OSCs achieve efficiencies of 19.82% and 20.06% with high open-circuit voltages (Voc) of 0.915 V and 0.925 V, respectively. This work highlights the potential of luminescent additives in suppressing non-radiative recombination, creating a viable avenue for the realization of low-energy-loss and high-efficiency organic photovoltaics.