Date of Award

2022

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Materials Science & Engineering

First Advisor

Shu Yang

Second Advisor

Christopher Murray

Abstract

Conventional cooling technologies not only consume substantial energy but increase the heat-trapping gases in the atmosphere. Passive cooling technologies such as radiative cooling and building envelope require little or no additional power input. Thus, they offer the most promising alternatives to address the ever-hot planet by efficiently reducing the energy consumption without adverse environmental impacts. In this dissertation, I have developed two types of passive cooling materials, including solar transparent and mid-infrared (MIR) radiative cooling mesoporous silica nanoparticles (MSNs) and kirigami-based dynamic shading envelope, for solar cells and building applications, respectively. The thermal stress decreases the photovoltaic performance and long-term stability because it induces critical and irreversible damage to the materials of the devices. Conventional cooling methods have been used to decrease the temperature of solar cells. However, they increase the cost because of the external energy input or increase in the system complexity. Here, I develop the innovative radiative cooler to efficiently decrease the temperature of perovskite solar cells (PSCs). In this part, MSNs of different pore diameters are synthesized to fine-tune the refractive index. The diameter of MSNs is controlled by pH, temperature, and reaction time. To manipulate pore diameter and volume, the ratio of the swelling agents and surfactants is controlled. MSNs with different pore diameters are stacked by solution process to fabricate the graded refractive index (GRI) structure on the PSCs, which shows high transmission in the solar wavelength region and high emission in the MIR region. The outdoor test over 20 days shows little change of the crystal structures of the perovskite, methylammonium lead iodide (MAPbI3), or change of the solar performance, whereas that without the coating is completely degraded. This strategy may open the new possibility for efficient cooling of PSCs. In the second approach, I fabricate kirigami-based dynamic shading envelopes with linear cuts from polyethylene naphthalate (PEN) film and analyze the light management of them in the real working condition. The interspace between the cutting lines is varied to fine-tune the degree of the opening of the envelope. Due to different interspaces and variable strains, kirigami envelopes with different opening gap areas are obtained to modulate the amount of light entering the building. The simulation is performed to investigate the effect of kirigami based dynamic envelope on light modulation and hence temperature inside the space. Well-controlled measurement system and in-depth simulation result in high consistency between experimental and simulation data, within the acceptable level (±1.6 oC). This work suggests that kirigami structures have great potentials in the building energy savings.

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