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.

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.…”

Stability Of Non‐Fullerene Electron Acceptors and Their Photovoltaic Devices

“…that T1:IT-4F solar cells could maintain 78% PCE after storing in ambient with continuous illumination for more than 1000 h (Figure 18e), and Han et al [116] demonstrated that PM6:Y6:PC 70 BM devices with appropriate interfacial layer allows only 20% PCE decrease after 480 h storing in air with illumination. Very recently, Zhang et al [117] applied an additive strategy to enhance the molecular stacking of Y6-BO molecules in the PM6:Y6-BO OSC, and improved its operational stability to a T 80 of 523 h, outperforming the reference device (without any additive treatment) with a T 80 of 66.2 h as well as the DIO treated OSC with T 80 of only 6.6 h.…”

“…Very recently, Zhang et al. [ 117 ] applied an additive strategy to enhance the molecular stacking of Y6‐BO molecules in the PM6:Y6‐BO OSC, and improved its operational stability to a T 80 of 523 h, outperforming the reference device (without any additive treatment) with a T 80 of 66.2 h as well as the DIO treated OSC with T 80 of only 6.6 h.…”

“…e) Normalized PCE of inverted PM6:Y6-BO device as a function of time upon photon-illumination under ambient. Reproduced with permission [117]. Copyright 2019, Wiley-VCH.…”

Balancing the Molecular Aggregation and Vertical Phase Separation in the Polymer: Nonfullerene Blend Films Enables 13.09% Efficiency of Organic Solar Cells with Inkjet‐Printed Active Layer

“…[38] Nevertheless, the NFA-based OSCs usually required quick dry, otherwise excessive aggregates would form and lead to poor performance. [31,[39][40][41] Thus, it would be more difficult to control the nanostructure and phase separation morphology of the NFA-based blend films, and is extremely challenging to achieve reasonable nanomorphology with weak aggregation that ensure efficient charge separation and transport. [42] As far as we know, there is rather limited research focused on the investigation of morphology characteristics and manipulation of the inkjet-printed NFA blend films.…”