| Summary: | The interactions of light and matter drive many of today’s devices, from electricity generation and consumption to manipulation. Within electricity generation, emerging thin film photovoltaics now rival traditional silicon-based solar cells in terms of power conversion efficiency (PCE) due to dramatic improvements to optoelectronic material properties and device architectures. Within electricity consumption, quantum dot light emitting diodes (QD-LEDs) are a high-efficiency, high color purity, versatile material candidate. Recent efforts to develop heavy metal-free QD-LEDs have led to high external quantum efficiencies in InP- and ZnSebased QDs rivaling the performance of the colloidal archetype of Cd-based QD-LEDs. Within energy manipulation, the emergence of photonics from electronics presents opportunities to engineer low-loss, low-threshold information transmission and computation by all-optical means and matter-mediated hybrid electronic/photonic processes.
In this work, we investigate light-matter interactions in emerging thin film perovskite photovoltaics, heavy metal-free QD-LEDs and microcavities, and two-dimensional perovskite microcavity exciton-polaritons.
First, we quantify the PCE enhancements due to photon recycling in high-efficiency Cs₀.₀₅(MA₀.₁₇FA₀.₈₃)₀.₉₅Pb(I₀.₈₃Br₀.₁₇)₃ (triple-cation) perovskite thin film photovoltaics as a function of material properties such as non-radiative recombination and the probability of photon escape. We determine that a perovskite active layer material with non-radiative rates k₁< 1x10⁴ s⁻¹ can result in practical PCE improvements of up to 1.8% due to photon recycling alone, and present material and device design principles to harness photon recycling effects in next-generation perovskite solar cells.
Next, we investigate energy and charge transfer in InP/ZnSe/ZnS QD thin films and QDLEDs as a function of increasing electric field strength. We probe the voltage-controlled photoluminescence (PL) modulation of a QD-LED in reverse bias and achieve 87% PL quenching, which is, to our awareness, the highest reported quenching efficiency in InP-based QDs. We also demonstrate amplified spontaneous emission processes in QD metallic microcavities by spectral coincidence of a three-dimensional confined photon mode and photon recycling-enhanced gain region.
Finally, we form exciton-polaritons (polaritons) at room-temperature in 2D perovskite microcavities resulting in, to the best of our knowledge, a record exciton-photon coupling strength for planar (C₆H₅(CH₂)₂NH₃)₂PbI₄ microcavities of ℏΩ subscript Rabi = 260 ± 5 meV. By utilizing wedged microcavities in which the cavity detuning is changed as a function of excitation position, we probe the temperature-dependent polariton photophysics for varying polariton exciton/photon character. In this way, we reveal material-specific polariton relaxation mechanisms and intracavity pumping schemes from the interplay of 2D perovskite excitonic states.
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