Light-Matter Interactions in High-Efficiency Photovoltaics, Light-Emitting Devices, and Strongly Coupled Microcavities

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.

Name thesis:degree_name

Doctoral

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2022

Author dc:creator

• Laitz, Madeleine Reynolds

Advisor dc:contributor.advisor

• Bulović, Vladimir

Statement dc:rights

• In Copyright - Educational Use Permitted
• Copyright MIT

Licence dc:rights.uri

• http://rightsstatements.org/page/InC-EDU/1.0/

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/144595

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/144595