Over 19.2% Efficiency of Layer‐By‐Layer Organic Photovoltaics by Ameliorating Exciton Dissociation and Charge Transport

Abstract Layer‐by‐layer (LbL) organic photovoltaics (OPVs) are fabricated with polymer PM1 as donor and small molecule L8‐BO as acceptor by employing sequential spin‐coating technology. The small molecule BTP‐eC9 and polymer PTAA are deliberately selected for individually incorporating into PM1 layer and L8‐BO layer, resulting in the power conversion efficiency (PCE) increased from 18.22% to 19.23%. The improvement of performance is attributed to the synergistically increased short circuit current density (J_SC) of 27.78 mA cm⁻² and fill factor (FF) of 78.23%. The introduction of BTP‐eC9 into PM1 layer can promote the photogenerated exciton dissociation, especially for the excitons near the anode. Meanwhile, molecular crystallinity of PM1 is also enhanced by incorporating appropriate BTP‐eC9 into PM1 layer. The incorporation of PTAA into L8‐BO layer can provide hole transport channels to effectively improve the transport of holes generated by the self‐dissociation of L8‐BO, resulting in the enhanced FFs from 77.40% to 78.23%. The synergistic effects of BTP‐eC9 and PTAA incorporation in donor and acceptor layers result in a 19.23% PCE of the optimized LbL‐OPVs. This work demonstrates that there is great room to hierarchically optimize donor and acceptor layers for achieving highly efficient LbL‐OPVs.