Integration of Multiple-Photon Excitation of Quantum Dots and Singlet Fission of Pentacene Dimers in Inorganic and Organic Hybrid Systems

Singlet fission (SF) is a spin-allowed multiexciton generation (MEG) process, where one singlet exciton (S₁) splits into two triplet excitons (2T₁) in two nearby molecules (theoretical maximum triplet quantum yield: 2). In contrast, bi- and multiexciton states of quantum dots (QDs) have been generated by exciting them at high excitation density (multiple-photon excitation). Here, we propose combining these materials for the integrated MEG (iMEG) process using 6,13-bis­(triisopropylsilylethynyl)­pentacene (TP) dimer [(TP)₂]-modified CdSe QD (CdSeQD) hybrids. Upon photoexcitation of CdSeQD with multiple-photon excitation, a sequential photoinduced process from the multiexciton state (CdSeQD) to SF [(TP)₂] occurred through singlet–singlet energy transfer (EnT) from CdSeQD to TP. The number of triplet excitons generated per CdSeQD (N_T) increased up to ∼4.9 ± 0.7 at higher excitation intensities. Our proposed inorganic–organic hybrid system demonstrates a novel exciton amplification process for various future uses, such as solar energy conversion, optoelectronics, and biological applications.