Highly volatile solid additives have attracted much attention recently because they enhance molecular packing order and possibly solve the problems of poor reproducibility and instability of polymer solar cells (PSCs) with solvent additives. The shortcoming is that existing solid additives require thermal annealing (TA) to remove them from the active layer, leading to an increase in the complexity of the device fabrication process and morphology rearrangement problems. This study introduces a commercially available, low-cost, and highly volatile material, naphthalene (NA), as a solid additive used in PSCs based on PM6: Y6. NA is well mixed with a non-fullerene acceptor and can restrict excessive aggregation of the donor and acceptor, producing efficiencies comparable to PSCs processed by 1-chloronaphthalene (CN) solvent additive. As a result, a maximum power conversion efficiency (PCE) of 16.52% for NA-processed PSC is achieved, higher than that of a PCE of 16.07% for CN-processed PSC with TA. NA-processed PSCs exhibit comparable efficiencies (PCE of 16.10%) without TA treatment and higher reproducibility/stability than CN-processed PSCs. This study demonstrates a low-cost and excellent volatile solid additive to improve the device performance and the potential for exploring new solid additives that can readily be made volatile without TA.

Volatile solid additives are an effective strategy for optimizing morphology and improving the power conversion efficiencies (PCEs) of organic solar cells (OSCs). Much research has been conducted to understand the role of solid additives in active layer morphology. However, it is crucial to delve deeper and understand how solid additives affect the entire morphology evolution process, from the solution state to the film state and the thermal annealing stage, which remains unclear. Herein, the use of a highly crystalline solid additive, phenoxathiin (Ph), in D18‐Cl:N3‐based OSCs and study its impact on morphology formation and photovoltaic performance is presented. Owing to its good miscibility with the acceptor N3, Ph additive can not only extend the time for the active layer to form from the solution state to the film state, but also provide sufficient time for acceptor aggregation. After thermal annealing, Ph solid additive volatilizes better aligned the N3 molecules and formed a favorable hybrid morphology. Consequently, the D18‐Cl:N3–based OSC exhibited an outstanding PCE of 18.47%, with an enhanced short‐circuit current of 27.50 mA cm−2 and a fill factor of 77.82%. This research is spurring the development of high‐performance OSCs using solid additives that allow fine control during morphology development.

Modifying the end-capping groups in nonfullerene acceptors (NFAs) is an effective strategy for modulating their properties and that of the entire NFAs. This study reports the synthesis of a novel γ-ester-functionalized IC end-capping group (IC-γe) and its incorporation into the benzothiadiazole-fused central core, yielding isomer-free IC-γe end-capped NFAs, such as Y-IC-γe, Y-FIC-γe, and Y-ClIC-γe. The resultant NFAs exhibited similar absorption profiles but upshifted the lowest unoccupied molecular orbital energy level compared with those of the ester-free analogues, such as Y6 and Y7. Without thermal annealing, an excellent power conversion efficiency (PCE) of 16.4% is realized in the annealing-free OSC based on Y-FIC-γe with the PM6 donor polymer, which outperforms the OSCs based on Y-IC-γe and Y-ClIC-γe. In addition, the OSCs based on asymmetric Y-FIC-γe and Y-ClIC-γe have higher thermal stability with more than 83% PCE retention at an elevated temperature after 456 h than the symmetric Y-IC-γe case. In this study, we not only establish the structure–property relationship regarding the ester functionality and symmetricity tuning on the NFAs but also diagnose the reasons for the best-performing Y-FIC-γe-based OSCs, providing useful information for a novel high-performing NFA design strategy.

Layer-by-layer (LBL) processing approach is recently under intensive investigation to fabricate efficient polymer solar cells (PSCs) reconsidering its many positive aspects over bulk-heterojunction configuration. Moreover, with recently reported successful solid...

A simultaneous further increase in the power conversion efficiency (PCE) and device stability of organic solar cells (OSCs) over the current levels needs to be overcome for their commercial viability. Herein, a bay‐area benzamide‐functionalized perylene diimide‐based electron transport layer, namely H75 is developed, to obtain the aforementioned characteristics. The advantages of H75‐employed OSCs include a notable PCE up to 18.26% and outstanding device stabilities under conditions of varying severity (>95% PCE retention after 1500 h upon long‐term aging and exceptional T80 lifetimes (the time required to reach 80% of initial performance) of over 1000 h in light‐soaking, 500 h in thermal stress at 85 °C, 72 h in 85% high relative humidity, and 100 h in atmospheric‐air conditions without encapsulation in conventional architecture). The excellent performance of H75‐employed OSC can be attributed to its various beneficial features derived from the bay‐area benzamide functionalities (e.g., excellent film‐forming ability, suitable energy level, reduced aggregation, and intrinsic high structural stability). The findings of this work provide further insights into the molecular design of electron transport layers  for realizing more efficient and stable OSCs.