CAREER: Toward Twenty Year Lifetime:Hermetic Sealing for Perovskite Solar Cells

Suny At Binghamton, Binghamton NY

Investigators

Abstract

Abstract: Non-technical description: While the vast majority of current solar cells are based on silicon technology, the cost of production and inability to achieve fabrication in a roll-to-roll platform overshadow its high efficiency and long-term reliability. A potentially superior solar technology is based on perovskites, which are crystalline minerals found in nature. Perovskite solar cells have already achieved efficiencies close to that of silicon cells. However, current perovskite solar cells are not usable due to toxicity concerns (lead is generally used to fabricate perovskites) and short lifetimes. The goal of this research project is to synthesize an efficient, affordable, and environmentally safe germanium perovskite solar cell. In addition to replacing lead by chemically similar but non-toxic germanium, inorganic layers, such as nickel oxide and tin oxide, will be explored as interfacial layers to improve stability. The devices will also be hermetically sealed with thin-film encapsulants, and characterized through accelerated testing to determine device lifetime. Lead perovskites have only lasted several months under ideal laboratory conditions. The proposed sealing techniques will enable module lifetimes to be greater than 20 years. The ability of these cells to be fabricated on a flexible substrate will further drive down the price of solar energy, helping solar energy to become less costly than fossil fuel derived energy. This project will provide multiple opportunities for graduate, undergraduate, K-12, and under-represented groups to engage in the next generation of renewable energy research. A new course on future energy materials will benefit a broad range of students with interest in material science and thin film devices. The findings of this work will provide the research community with a greater understanding of the fundamental properties of this new perovskite material, and provide industry with the information needed for commercialization. Technical description: In this work, germanium perovskite will be synthesized to build highly efficient, stable, and environmentally benign solar cells. The proposed germanium perovskites will overcome the deficiencies of lead-based perovskites including toxicity, interfacial layer instability, and limited lifetime. The project is two-fold: high quality germanium perovskite will be synthesized and characterized and then stabilized through thin-film encapsulants and inorganic interfacial layer selection. Germanium perovskites display excellent photovoltaic properties such as high optical absorption, high carrier mobility, and direct band gap. However, previous attempts were unsuccessful due to poor film morphology. A solvent-engineering approach will be used to achieve high-quality germanium-based perovskite. The perovskite's interfacial charge transport layers will be inorganic in nature to allow for greater device stability than can be achieved with organic layers. A solid-state reducing atmosphere will be used to prevent oxidative damage to the perovskite due to slow ingression of moisture and water over time. In addition, atomic layer deposition (ALD) grown metal-oxide barriers will cap the finished device, followed by a final epoxy sealing. The resulting hermetic seal will be characterized through helium and calcium leak tests, from which the expected module lifetime can be extrapolated. This sealing technique is anticipated to enable device lifetimes in excess of 20 years. The proposed work will provide a fundamental understanding of germanium perovskite synthesis, model the lifetime of encapsulated solar device, and play a critical role in achieving stable, low-cost, and environmentally safe solar cells.