Browsing by Author "Iyer, Abhishek Radhakrishna"
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Item Understanding and optimizing the performances of PEDOT:PSS based heterojunction solar cells(University of Delaware, 2021) Iyer, Abhishek RadhakrishnaClimate change is and will be one of the greatest challenges facing humankind. The effect of global warming is being felt on a day-to-day basis across the globe. Our energy mix still has a strong reliance on fossil fuel based technologies but we have acknowledged the urgency and have started adopting the route of renewables. Amongst renewables, solar and wind are the fastest and most promising renewable energy technologies to constitute the energy mix. With rapid technological progress and cost decline in the last decade, silicon based photovoltaics are the torch-bearers to this energy revolution. The global solar PV panels market size was valued at USD 115.2 billion in 2019 and is projected to grow at a compound annual growth rate (CAGR) of 4.3%-5.6% from 2020 to 2027 [1]. Today, the most dominant solar PV technology is silicon based solar that constitutes over 90% market share. Silicon solar cells have demonstrated high power conversion efficiencies, reliability over 25 years and a pathway to improved performances. Despite the high growth and adoption rate in the past decade, the capital-intense nature of silicon PV manufacturing limits the sustainable growth of this industry. High temperature processing is necessary for such cell technologies but they several disadvantages- high capital expenditure (CAPEX) and operating costs (OPEX), inability to process thin wafers easily and silicon impurities getting activated during the high-temperature steps leading to reduced minority carrier lifetimes and higher losses. ☐ This thesis focusses on an alternative approach to processing silicon based solar cells by relying on low-temperature and solution-based processing. In contrast to homojunction or amorphous silicon-based heterojunction (Si-HJT) solar cells, we take the route of realizing heterojunctions on silicon via spin coating. The carrier selective induced junction solar cells demonstrate a heterojunction like solar architecture with an organic polymer, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) as the emitter and crystalline silicon as absorber. The role of PEDOT:PSS in this heterojunction architecture is pivotal since it plays a dual role- inducing a junction and hole transport layer. These heterojunction solar cells are termed as hybrid silicon solar cells too since they blend the maturity of silicon as the absorber and tunability of organics. We also traverse the path of investigating the degradation mechanism and reliability of these solar cells, first of a kind work on this field for such cell architectures. The front-junction hybrid cells made in this dissertation effort have demonstrated 12.4% power efficiencies at lab scale and are comparable to record efficiency hybrid solar cells with similar architecture from other labs. Most importantly, we establish a framework and pathway to superior performances and future work for PEDOT:PSS based heterojunction silicon solar cells. The potential commercial impact, entrepreneurial efforts and running a startup company from the perspective of a graduate student will also be discussed in the end.