Augmented Photoluminescence in a Conjugated Polymer by the Incorporation of CdSe/CdS Quantum Dots

Abstract

We investigated the photophysical interactions between CdSe/CdS quantum dots (QDs) and a conjugated polymer (CP, P3HT). The photoluminescence intensity of P3HT in the QDs/P3HT hybrid system is significantly enhanced compared to that of the neat P3HT system. We found via transient absorption spectroscopy that the energy level differences at the interfaces between P3HT and QDs resulted in delayed relaxation dynamics of the P3HT singlet (S 1 ) excitons and suppressed polaron formation. Thus, the radiative recombination of the S 1 excitons occurs frequently in the hybrid system than in the neat P3HT system. Our findings on the CPbased hybrid system may provide important information to improve the efficiencies of optoelectronic devices, such as organic light-emitting diodes.

Fluorination-Induced Conversion of the Quasi- to the Normal Interchain Packing in Push–Pull Conjugated Polymer Aggregates

“…Push–pull conjugated polymers (CPs) have emerged as alternative electron donor materials, replacing first-generation CPs like poly­(3-hexylthiophene), and have become the mainstream materials in the field of bulk heterojunction (BHJ) organic solar cells (OSCs). − Extensive research has been conducted on exciton dynamics in various push–pull CP systems, where the chain backbone consists of alternating electron-rich and electron-deficient units. − In the organic CP aggregate systems with low dielectric constants, singlet (S 1 ) excitons with excess energy can give rise to excited-state species such as polaron pairs (loosely bound charge carriers) and separated polarons (free carriers), referred to as quasi-charge-transfer (CT) states with lower binding energy compared to Frenkel excitons. ,− The formation mechanisms of polaron states, i.e., exciton dissociation, are influenced by chain rigidity, length, and aggregation pattern. , Furthermore, CP chains at the interfaces with electron acceptors exhibit more disorder than the chains in pure CP domains away from the interfaces within the BHJ blends . Therefore, unraveling the exciton dynamics dependent on these factors within the push–pull CP aggregates is crucial for understanding the exciton dissociation and carrier diffusion dynamics in high-efficiency BHJ OSCs.…”