Abstract
Herein, an insulating biopolymer is exploited to guide the controlled formation of micro/nano-structure and physical confinement of α-δ mixed phase crystalline grains of formamidinium lead iodide (FAPbI3) perovskite, functioning as charge carrier concentrators and ensuring improved radiative recombination and photoluminescence quantum yield (PLQY). This composite material is used to build highly efficient near-infrared (NIR) FAPbI3 Perovskite light-emitting diodes (PeLEDs) that exhibit a high radiance of 206.7 W/sr*m2, among the highest reported for NIR-PeLEDs, obtained at a very high current density of 1000 mA/cm2, while importantly avoiding the efficiency roll-off effect. In depth photophysical characterization allows to identify the possible role of the biopolymer in i) enhancing the radiative recombination coefficient, improving light extraction by reducing the refractive index, or ii) enhancing the effective optical absorption because of dielectric scattering at the polymer-perovskite interfaces. Our study reveals how the use of insulating matrixes for the growth of perovskites represents a step towards high power applications of PeLEDs.
Highlights
Halide perovskites are currently explored as active materials in light-emitting diodes (LEDs) with very promising outcomes[1,2]
Near-infrared LEDs, exploiting the peculiar prerogatives of perovskite FAPbI3/starch active layer, was successfully developed reaching an impressive radiance value of 206.7 W/sr*m2 obtained at very high currents density of ~1000 mA/cm[2], a value never yet reported for IR emitting PeLEDs12
Though X-ray diffraction we found that starch leads to the formation of mixed domains of α and δ FAPbI3 phases, a crystalline scenario that have been proven to reduce the local dielectric landscape and the material average grain size, increasing the exciton binding energy and the spatially confinement of the excitons[24], eventually leading to PLQY enhancement and to blue shift of the emission peak upon starch addition with respect to the reference
Summary
Halide perovskites are currently explored as active materials in light-emitting diodes (LEDs) with very promising outcomes[1,2]. The increased spatial confinement tends to increase Auger recombination rates, so that strategies that boost emission of PeLEDs at low current densities end up in causing an efficiency roll-off at high currents[12] Preventing this phenomenon is of paramount importance and presently only few work have tried to address it, among those the most successful strategy resulted to be the tuning of the quantum well width, in 2D/3D, leading to a reduction in the local carrier density[12]. We report a simple method to engineer the phase composition and to finely tune the grain sizes of perovskite with the precise scope of sustaining high radiance at elevated current density regimes, restraining the roll-off effect This was achieved by using starch biopolymer as templating agent for the growth of formamidinium lead iodide (NH2CH2NH3PbI3 or FAPbI3) 3D perovskite grains[20,21]. The better coverage of the substrate obtained with polymer improves the active interfaces leading to high current densities
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
