Controlling the Spin Exchange Energy through Charge Transfer for Triplet State Management in Organic Semiconductors

Abstract

Optoelectronic devices fabricated from organic semiconductors, such as organic light emitting diodes (OLEDs) and photovoltaics (OPVs), have reached the point of viability in real-world applications. However, despite the rapid recent progress in the field, open questions remain around the role and management of spin-triplet states in these systems. In this perspective, we discuss recent advances in the manipulation of triplet states, with a particular focus on strategies that involve modulating the spin exchange energy through tuning the degree of charge transfer character in the excited state. We explore the equivalence between the localized and delocalized electronic excited state manifolds in OLEDs and OPVs and propose strategies for aligning the designs of OPVs with those of OLEDs. We consider that lessons from the successful triplet management strategies in the OLED field hold the key for improving the radiative efficiency of OPVs, which is necessary to drive power conversion efficiencies toward the important milestone of 20% and beyond.

Pt(II)-Bisacetylide ‘Roller Wheels’: Molecular Engineering towards Small Bandgap, High Crystallinity, and Controlled Triplet Exciton Processes

“…This large bathochromic shift also suggests efficient electronic delocalization of singlet excited states in the solid state that is an effective means of reducing singlet–triplet energy gaps. 42 Preliminary calculation results for RWPt-4 are shown in Figure 8 . The presence of strongly electron-withdrawing DCI units leads to spatially separated HOMO and LUMO, respectively, concentrated at the Pt-benzenedithiophene core and DCI units.…”