Cyano-functionalized pyrazine: an electron-deficient unit as a solid additive enables binary organic solar cells with 19.67% efficiency

The morphology of the photoactive layer plays an important role in both the photoelectric effect and device performance of solution‐processed organic solar cells (OSCs). Optimizing the morphology requires precise control over the complex film formation kinetics, which are influenced by a range of factors from the solution state to the solid‐film state. This review delves into the in situ characterization technologies employed to understand the active layer formation process and explores strategies for controlling film formation during key stages, including solution aggregation, nucleation, crystal growth, and phase separation. Special attention is given to the mechanism by which these strategies enable real‐time morphology control during the printing process and their potential to facilitate direct printing of active layers with optimized morphology. The goal is to offer valuable insights and guidance for managing film formation kinetics in solution‐processed OSCs, ultimately addressing the challenges of real‐time morphology control in scale‐up printing and paving the way for high‐throughput production of post‐processing‐free devices.

In Situ Morphology Control for Solution‐Printable Organic Photovoltaics

Bi,

Liu,

2024

17.2% Efficiency for Completely Non‐Fused Acceptor Organic Solar Cells Via Re‐Intermixing Strategy in D/A Stratified Active Layer

Xie,

Ma,

Zhang

et al. 2024

Pursuing power conversion efficiency (PCE) is the priority of developing organic solar cells (OSCs) based on low‐cost completely non‐fused ring acceptors. Herein, a donor/acceptor re‐intermixing strategy to enhance the photon capturing process, based on a previously established well‐stratified active layer morphology is reported. By adding 20 wt% PTQ10 (polymer donor) into the acceptor's precursor, the device PCE is increased to 16.03% from 15.11% of the D18/A4T‐16 control system, which is attributed to the additional charge generation interface and suppressed bimolecular recombination. On the contrary, using the equal ratio of PM6 leads to significant efficiency loss, indicating the importance of considering vertical distribution from the perspective of thermodynamics. Moreover, a cutting‐edge level of 17.21% efficiency for completely non‐fused ring acceptor systems is realized by altering the active layer to PBQx‐TF/TBT‐26 and PTQ11, via the identical processing strategy. This work thus presents attractive device engineering and solar cell performance, as well as in‐depth vertical morphology understanding.

Asymmetric π‐Bridge Strategy Regulating Film‐Forming Kinetics for Over 19% Efficiency Organic Solar Cells

Wang,

Bi,

Jiang

et al. 2024

Blending morphologies are critical to bulk‐heterojunction (BHJ) organic solar cells (OSCs) to realize satisfactory photovoltaic performance. Therefore, rationally manipulating film‐forming kinetics is of great importance to building suitable phase‐separations to balance exciton dissociation and charge transport. Herein, by employing a unilateral π‐bridge approach, a new acceptor, WA6 is reported to optimize the film‐forming process of active layers and their microstructures. Meanwhile, the possible influencing factors are proposed, including intermolecular electrostatic interactions and donor/acceptor compatibility in the vital solution‐to‐film transformation stage. Beneficial from the appropriate fibrous phase‐separation, the PM6:WA6 based solar cells refined exciton/charge properties, leading to 15.39% high efficiency and much greater than the control device based on the counterpart acceptor without π‐bridge. Furthermore, the WA6 can serve as efficient guest component as well, and achieved 19.21% efficiency in the resultant ternary solar cells. This study provides a feasible approach to modulate the molecular aggregation and film‐forming procedure, for the construction of high‐performance OSCs with eligible blending morphologies.