With the global energy demand projected to grow rapidly, it is imperative to divest from traditional greenhouse gas-based power production toward renewable energy sources such as solar. In recent years, solar photovoltaics (PV) hold a large share among renewables sources. Currently, the market is dominated by crystalline silicon solar cells due to their low levelized cost of energy (LCOE) values. However, to sustain this progress, the power conversion efficiency of PV devices must be further improved since tiny costs cut from the other expenses is difficult. On the other hand, the margin for the PCE improvement in c-Si technology is also quite limited since the technology is approaching its practical limits. At this stage, coupling c-Si devices with another efficient solar cell in tandem configuration is a promising way to overcome this challenge. Perovskite solar cells (PSCs) represent a breakthrough solar technology to enable this target due to their proven high efficiency and potential cost-effectiveness. Whereas perovskite/silicon tandem solar cells are promising, their operational stabilities are still a significant concern for market entry. Here, the degradation mechanism of n-i-p perovskite/Si tandem solar cells was investigated. Thermal stability tests have shown severe degradation in such tandem devices. On the other hand, tandem devices were relatively stable when placed in a humidity cabinet with 25% relative humidity (RH). Conversely, temperature degraded devices showed cracks all over the perovskite surface and rupture in the top electrode after 1000 hrs at 85 oC. Additionally, silver iodide formation was depicted in XRD and XPS analysis. To enhance the stability, methods to reduce the hysteresis were studied. First, potassium chloride (KCl) was applied as a passivation agent to the electron transport layer (ETL) to reduce surface defects. Second, 2D passivation was applied to reduce trap density and enhance the crystallinity of the perovskite film. Finally, organic molecules were placed between the hole transport layer (HTL) and metal-oxide interface as interlayers to prevent diffusion of metal oxide to the HTL and accumulation of the dopant at the metal-oxide interface. After passivation and interface layers, stability enhanced but further improvement is still required.
|Date made available
|KAUST Research Repository