Energy transfer in ternary blend organic solar cells: recent insights and future directions

Abstract

Resonance energy transfer (RET) can potentially improve the device efficiencies of ternary blend organic solar cells (TBSCs). However, several parameters, such as domain morphology, exciton lifetime, energy and charge transfer, influence the resulting photophysics. Owing to this, spectroscopic studies on TBSCs have not unambiguously deconvolved the role of RET in the observed enhancement of photocurrent densities, often downplaying the mechanistic aspects of the RET associated enhancement. In this perspective, we discuss and analyse the role of RET in enhancing the device efficiency by taking a few recent examples of TBSCs. Taking analogy from natural photosynthetic systems, we argue that deviations in the observed RET rates from a Förster type mechanism may be at play. We suggest new strategies to systematically correlate the Förster critical distance (R₀) with increments in current density (ΔJ_SC) in order to gain mechanistic insights to optimize RET enhanced photocurrent for high efficiency organic solar cells.