φ ET1 = 100 × (neat PbS film emission-UC film PbS emission) Neat PbS film emission Equation Promisingly, we observed an increase in quenching efficiency with increasing TCA concentrations (see Figure ). For all concentrations of PbS, without the introduction of TCA, less than 80% of the PbS emission is quenched (orange bars in Figure ). In stark contrast, the PbS emission from 5 and 10 mg/mL PbS films are almost completely quenched when 3 or 6 mM TCA is introduced as an interlayer between PbS and rubrene (blue and yellow bars in Figure ). In particular, we note that for 50 mg/mL PbS films, the quenching efficiency rises from approximately 75% to over 85% upon the introduction of 6 mM TCA. This increased quenching efficiency with the introduction of TCA provides evidence of an increase in the Dexter energy transfer efficiency (φET1) from PbS to the organic layers.