LAUSR

The layer-by-layer (LbL) solution-processed active layer of organic solar cells (OSCs) is conductive to achieve vertical phase separation, tunable donor/acceptor (D/A) interfaces and favorable charge-transport pathways. This technique also enables facile film morphology adjustment to enhance device performance by introducing a volatile additive or a third component to the D/A system. In this work, we add a wide-bandgap component poly(9-vinylcarbazole) (PVK) into the upper electron acceptor layer to improve the performance of LbL-processed OSCs. Results show that the PVK component can adjust the film morphology, dope the electron acceptor, increase the electron concentration and improve charge transport. Such an n-type doping is verified by Seebeck coefficient measurement, ultraviolet photoelectron spectroscopy and electron paramagnetic resonance characterization. In addition, the fluorescence intensity and exciton lifetime of the PVK-doped acceptor film are increased, thus being beneficial for exciton diffusion to the D/A interface. As a result, the power conversion efficiency (PCE) of LbL OSCs increases from 16.02% to 17.00% when 2.50 wt% PVK is employed in the electron acceptor layer for the PM6/BTP-eC9-4F active layer and from 18.70% to 19.05% for the D18/L8-BO system when 0.50 wt% PVK is introduced. The role of PVK played in the active layer is different from those of additives and ternary components reported previously, so our results provide an alternative way to enhance the device performance of LbL-processed OSCs. This article is protected by copyright. All rights reserved.