Introducing a third component into organic bulk heterojunction solar cells has become an effective strategy to improve photovoltaic performance. Meanwhile, the rapid development of non-fullerene acceptors (NFAs) has pushed the power conversion efficiency (PCE) of organic solar cells (OSCs) to a higher standard. Herein, a series of fullerene-free ternary solar cells are fabricated based on a wide bandgap acceptor, IDTT-M, together with a wide bandgap donor polymer PM6 and a narrow bandgap NFA Y6. Insights from the morphological and electronic characterizations reveal that IDTT-M has been incorporated into Y6 domains without disrupting its molecular packing and sacrificing its electron mobility and work synergistically with Y6 to regulate the packing pattern of PM6, leading to enhanced hole mobility and suppressed recombination. IDTT-M further functions as an energy-level mediator that increases open-circuit voltage (V OC ) in ternary devices. In addition, efficient Förster resonance energy transfer (FRET) between IDTT-M and Y6 provides a non-radiative pathway for facilitating exciton dissociation and charge collection. As a result, the optimized ternary device features a significantly improved PCE up to 16.63% with simultaneously enhanced shortcircuit current (J SC ), V OC , and fill factor (FF).
[9406][9407][9408][9409][9410] adsorption the contribution of double-layer charging may be removed via background subtraction where the background is estimated from the same voltammetric response prior to the onset of the faradaic current. This eliminates the need for additional experiments to determine the contribution of double-layer capacitance.Furthermore, the potential of semiintegral analysis to determine surface concentration in the presence of fast surface phenomena suggests that its use may be extended to other areas of electrochemical interest. The thin-layer model discussed herein is one such example which can be extended to the study of thin films where the concentration of redox species within the film is affected by partitioning into or out of the film. Of interest would be the use of semiintegral analysis for the identification and quantitation of strong adsorption involving more complex isotherms which take into consideration interactions between adsorbed species, and the use of semiintegration analysis for kinetic and mechanistic studies in the presence of weak adsorption and thin films.
Acknowledgment.The spatial monitoring of ion diffusion into an ultrathin film sample was demonstrated by our depth profiling method using variable observation angle fluorescence spectroscopy under normal incidence conditions. A 143-nm-thick LB multilayer model sample was prepared in which the fluorophore rhodamine B was homogeneously distributed in each layer. The model sample was then immersed into an aqueous solution of sodium tungstate, where the tungstate ion diffused into it and r e a d with rhodamine B to form a nofluorescent complex. Because of this chemical quenching effect, the homogeneous concentration distribution of rhodamine B was changed by the tungstate ion diffusion. Changes in concentration depth profiles of rhodamine B with diffusion time were measured by the variable observation angle fluorescence depth profiling method based on the reciprocal theory, which has a spatial resolution of the monolayer thickness level in the depth direction. As a result, the diffusion behavior of tungstate ion was monitored, and its diffusion coefficient in LB multilayers was obtained as (1.2 -1.7)x 10-l' cm2/s.
The fabrication of organic solar cells (OSCs) by a layer‐by‐layer (LBL) method has attracted growing attention in recent years. As already known, the pre‐aggregates of conjugated polymers in solution have a profound impact on their microstructure morphology in films. Herein, by simply controlling the solution temperature and annealing processes, the pre‐aggregation behavior of D18 polymer in solution can be fine‐tuned and the microstructure of D18 bottom layer is well manipulated. The optimized D18 bottom layer can effectively regulate L8‐BO upper‐layer‐forming suitable networks for efficient charge transportation. In addition, a vertical phase separation with a special D/D:A/A structure (P‐i‐N‐type component distribution) is also formed. As a result, compared to the 16.43% power conversion efficiency (PCE) of the bulk heterojunction devices, such control enables bilayer OSC devices based on the polymer D18 and L8‐BO to deliver an enhanced PCE of 18.02% with simultaneously improved short‐circuit current density, open‐circuit voltage, and fill factor. It is also demonstrated in these results that the LBL deposition process utilizing the pre‐aggregation of polymer and its fiber‐network‐forming ability is a very promising approach to improve charge dynamics, suppress carrier recombination, and fabricate highly efficient OSCs.
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