Outdoor Stability of Triplet Generating and Triplet Harvesting Materials; Pentacene and Tetracene Electron Donors Merged with Boron Subphthalocyanines as Electron Acceptors

• Published in: ACS applied energy materials Vol. 6; no. 5; pp. 3061 - 3070
• Main Authors: Tetreault, Adam R., Mandlik, Ajinkya, Wojtkiewicz, Kacper, Nova, Kyle, Bender, Timothy P.
• Format: Journal Article
• Language: English
• Published: American Chemical Society 13.03.2023
• Subjects: outdoor; electronics; singlet; fission; testing; solar; cell; stability; organic; photovoltaics
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.2c04185

Triplet harvesting is a useful property that could enhance the performance of solar cells if applied in the right framework. There are currently few functional examples of organic solar cells (OSCs) capable of triplet harvesting, but materials are already under development. The improved current density output has already been realized, but the viability of working devices needs to be confirmed to advance this technology further. Here, we find that the outdoor stability of encapsulated devices can be improved significantly if triplet harvesting is enabled between the donor and acceptor. We compared the stability of pentacene/BsubPcs (boron subphthalocyanines) devices simultaneously and controlled the triplet harvesting capability by adjusting the peripheral chlorination on the BsubPcs. Pentacene/Cl–Cl12BsubPc devices which also exhibited the best triplet harvesting ability for this study experienced the least amount of degradation, not only was the stability improved when compared to other pentacene/BsubPc devices but these devices also had the highest stability of any that were tested including other singlet and triplet harvesting devices. This is promising for both the singlet fission donors and triplet harvesting acceptors involved and for triplet harvesting as a mechanism in totality. During this study, we also confirmed that some materials such as tetracene have insufficient thermal stability in devices. We also studied the relevant stability of single nanolayers of these materials. For example, single layer tetracene films seemed relatively stable without encapsulation even in harsh aging conditions but when incorporated into encapsulated OSC devices, the performance decreased quickly. Additional data acquired regarding tetracene also showed that even in the absence of light, OSC device performance decreased rapidly at elevated temperatures and may indicate that a nanomorphological change occurs; unless the nanomorphology can be passivated, we can conclude that tetracene may be difficult to incorporate into OSCs in the future.