Asymptotic Efficiency in OLEDS

TL;DR

This paper extends the theoretical analysis of asymptotic efficiency in OLEDs to multi-mode devices with isotropic emitters, exploring various configurations and emission mechanisms affecting efficiency and droop.

Contribution

It provides a comprehensive theoretical framework for understanding efficiency limits in complex OLED structures with different emitter orientations and emission types.

Findings

Efficiency equations for isotropic emitters at anti-node and node locations

Identification of conditions leading to linear output or second order losses

Analysis of spontaneous and stimulated emission effects on device performance

Abstract

Asymptotic efficiency (high output without droop) was recently reported for OLEDS in which a thin emitter layer is located at the anti-node in a resonant microcavity. Here we extend our theoretical analysis to treat multi-mode devices with isotropic emitter orientation. We recover our efficiency equations for the limiting cases with an isotropic emitter layer located at the anti-node where output is linear in current, and for an isotropic emitter located at the node where output can exhibit second order losses with an overall efficiency coefficient that depends on loss terms in competition with a cavity factor. Additional scenarios are described where output is driven by spontaneous emission, or mixed spontaneous and stimulated emission, with stimulated emission present in a loss mode, potentially resulting in cavity driven droop or output clamping, and where the emitter layer is a host-guest system.