Simultaneously Enhanced Efficiency and Operational Stability of Nonfullerene Organic Solar Cells via Solid‐Additive‐Mediated Aggregation Control

Abstract

The additive strategy is widely used in optimizing the morphology of organic solar cells (OSCs). The majority of additives are liquid with high boiling points, which will be trapped within device and consequently deteriorate performance during operation. In this work, solid but volatile additives 2‐(4‐fluorobenzylidene)‐1H‐indene‐1,3(2H)‐dione (INB‐F) and 2‐(4‐chlorobenzylidene)‐1H‐indene‐1,3(2H)‐dione (INB‐Cl) are designed to replace the common 1,8‐diiodooctane (DIO) in nonfullerene OSCs. These additives present during solution casting but evaporate after moderate heating. Molecular dynamics simulations show that they can reduce the adsorption energy to improve π‐π stacking among nonfullerene acceptor (NFA) molecules, an effect that enhances light absorption and electron mobility. Both INB‐F and INB‐Cl enhance efficiency, with INB‐F achieving a maximum efficiency of 16.7% from 15.1% of the reference PBDB‐T‐2F (PM6):BTP‐BO‐4F (Y6‐BO) cell, and outperforming DIO. Remarkably, they can simultaneously enhance the operational stability, with the INB‐F‐treated OSC maintaining over 60% of the initial efficiency after 1000 h operation, demonstrating a T80 lifetime of 523 h, which is a significant improvement over T80 values of 66.2 h for the reference and 6.6 h for DIO‐treated OSC. The simultaneously enhanced efficiency and operational lifetime are also effective in PM6:BTP‐BO‐4Cl (Y7‐BO) OSCs, demonstrating a universal strategy to improve the performance of OSCs.

Achieving Record-Efficiency Organic Solar Cells upon Tuning the Conformation of Solid Additives

“… 24 − 26 The second type of SADs can effectively decrease the adsorption energy of acceptors to improve π–π stacking through the attractive interaction between the SADs and acceptors, thereby resulting in an enhancement of light absorption and electron mobility. 27 , 28 The last type of SADs with high crystallinity can form well-developed nanoscale phase separation by restricting the over self-aggregation of acceptors in the process of film formation and then facilitating the donors to access the remaining space of SADs during the TA process. 29 , 30 Although these new strategies of SADs have shown many attractive features, the fundamental understanding of the relationship of SAD structures, active layer morphology, and OSC performance is missing.…”

High‐Efficiency Sequential‐Cast Organic Solar Cells Enabled by Dual Solvent‐Controlled Polymer Aggregation

“…It appears that the dual solvent affected the crystalline order of D18-Cl. [38][39][40] The absorption spectrum of the D18-Cl/Y6 bilayers is detailed in Figure 2b, with the peak around 550 nm attributed to D18-Cl and the peak around 800 nm being the contribution of Y6. The films of D18-Cl(CB þ CF)/Y6 and D18-Cl(CB þ THF)/Y6 displayed increased absorption throughout the spectral range, mainly in 400-600 nm, further suggesting that the dual solvent improved the crystallization of D18-Cl, making it more ordered, while protecting D18-Cl from being washed out and improving photon utilization.…”

Solid additives in organic solar cells: progress and perspectives

“…Solvent additives accelerate the burn-in degradation process of the active layers, while the solid additives significantly suppress the process due to their volatility. The results indicated that the solid additive is a promising material in OSC manufacturing as it improves the photostability and PCE 76 It appeared that the D-A-type structure is not essential for small organic additives to have positive effects in OSCs. For instance, a dihalogenated indanone end group IC-FI (Fig.…”