Tuning the polarity of organic magnetic field effects in polymer light-emitting diodes by incorporating a colloidal quantum dots thin layer

Organic magnetic field effects (MFEs) have attracted a lot of interests in foundation research and practical applications. In this work, a thin layer of colloidal quantum dots QDs was incorporated into the planar heterojunction-based polymer light-emitting diodes (PLEDs) as a sensitizer to tune the organic MFEs. As a result, the magneto-electroluminescence (MEL) and magneto-conductance (MC) in the poly[2-(4-(3',7'-dimethyloctyloxyphenyl)-1,4-phenylene vinylene)] (P-PPV)-based PLEDs can be tuned synchronously from positive to negative. The current and temperature dependences of the negative MEL and MC were studied elaborately, showing normal and anomalous dependences compared to those of typical positive MEL and MC, respectively. The underlying mechanism of negative MEL and MC was examined. It is revealed that efficient Forster energy transfer between P-PPV and QDs is responsible for the effective tuning of MEL and MC via promoting the reverse intersystem crossing between electron-hole pairs.