Global energy demand and climate change necessitates the rapid adoption of sustainable energy technologies. However, current systems often depend on scarce, toxic, or expensive materials such as tellurium and indium that bottleneck such advancements. This thesis addresses these limitations by developing Earth-abundant alternatives for thermoelectric and photovoltaic applications, focusing on three areas: magnesium pnictide thermoelectrics, indium-free transparent conductive oxides, and light management in photovoltaics via surface texturing. Thermoelectric materials convert temperature gradients into electricity via the Seebeck effect. Their performance is defined by the figure of merit (𝑍𝑇), which depends on high electrical conductivity, high Seebeck coefficient, and low thermal conductivity. This thesis explores undoped Mg3Bi2 and Mg3Sb2 thin films as tellurium-free alternatives to the current state-of-the-art Bi2Te3. The thermal co-deposition of Mg and Bi enables the tuning of stoichiometry between p-type (Mg-deficient) and n-type (Mg-rich) conduction, a characteristic essential in thermoelectric generators. Mg3Bi2 reveals strong performance: p-type films exhibit high carrier concentration but limited mobility, while n-type films achieve significantly higher mobility, lower thermal conductivity, and a 𝑍𝑇 up to 0.19. Mg3Sb2 reveals p-type conduction with inferior performance due to stoichiometric limitations but remains promising with further optimization. Photovoltaics convert light into electricity through charge generation and separation in semiconductors. Perovskites are emerging as next-generation materials for efficient thin-film solar cells because of their tunable bandgaps and strong optical absorption. However, this rapidly developing technology, similar to the display industry, still relies on indium tin oxide (ITO) as the transparent conductive oxide, which is limited by indium scarcity. This thesis demonstrates aluminum zinc oxide (AZO) as a viable alternative using room-temperature pulsed laser deposition (PLD). Optimized AZO films exhibit high conductivity exceeding 1 × 105 S m−1 and over 80% optical transparency in the visible spectrum. The AZO films remain stable under prolonged thermal stress in air and prove to successfully replace ITO in perovskite solar cells, achieving efficiencies up to ~19.4% across multiple architectures (superstrate, substrate and semitransparent), with long-term stability comparable to ITO-based devices. These thin-film solar cells suffer from optical losses within the device architecture. Therefore, we introduce the wet-chemical etching of AZO films using ammonium hydroxide to create nanoscale surface textures, effectively reducing reflection losses at the AZO/perovskite interface. These textures reduce reflection by forming an effective refractive index gradient that improves light coupling into the absorber. Additionally, the textured surface modifies perovskite growth, increasing layer thickness and enhancing absorption. As a result, short-circuit current density improves substantially (from ~22.4 to 24.6 mA cm−2), leading to power conversion efficiencies up to 20.1% in indium-free solar cells, surpassing flat-reference devices. This thesis combines thermal co-deposition and PLD with comprehensive material characterization techniques, including thermoelectric and photovoltaic measurements. Overall, we demonstrate that sustainable, high-performance alternatives to critical materials are achievable. Magnesium pnictides offer tellurium-free thermoelectrics with tunable properties through thermal co-deposition and PLD-AZO can be employed as a scalable replacement for indium-based transparent conductive electrodes, while surface texturing enhances photovoltaic efficiency of perovskite solar cells through improved light management. Together, these advances contribute to the development of cost-effective, environmentally benign energy technologies capable of supporting future global energy demands.
2026-09-18
