Unlocking Photoluminescence in 6,13-Bis(triisopropylsilylethynyl)pentacene: Singlet Fission Mitigation by 2D Material-Controlled Molecular Packing.

Organic photoluminescent semiconductors hold significant potential for bioimaging, sensing, and light emitting devices. However, their practical use in optoelectronics is often limited by aggregation-caused quenching (ACQ) that drastically reduces the photoluminescence (PL) quantum yields in densely packed solids. Here we report the controlled molecular packing of 6,13-bis(triisopropylsilylethynyl)pentacene (TPn), a model organic semiconductor that typically exhibits negligible PL due to ultrafast singlet fission in its crystalline form. Using monolayer WS2 (ML-WS2) as a growth substrate, we induced a transition from a standing-up to a reclining molecular orientation of TPn interfacial layers, effectively suppressing singlet fission and unlocking its PL emission. The type-I energy level alignment at the TPn/ML-WS2 heterointerface further enhances TPn emission by exciton energy transfer from ML-WS2. This work provides an effective approach for tailoring the molecular packing of weakly emitting π-conjugated solids using two-dimensional nanomaterials, facilitating their application in optoelectronic devices.