Toward Stable Monolithic Perovskite/Silicon Tandem Photovoltaics: A Six-Month Outdoor Performance Study in a Hot and Humid Climate

Abstract

Perovskite/silicon tandem solar cells are emerging as a highefficiency and prospectively cost-effective solar technology with great promise for deployment at the utility scale. However, despite the remarkable performance progress reported lately, assuring sufficient device stabilityparticularly of the perovskite top cellremains a challenge on the path to practical impact. In this work, we analyze the outdoor performance of encapsulated bifacial perovskite/silicon tandems, by carrying out field-testing in Saudi Arabia. Over a six month experiment, we find that the open circuit voltage retains its initial value, whereas the fill factor degrades, which is found to have two causes. A first degradation mechanism is linked with ion migration in the perovskite and is largely reversible overnight, though it does induce hysteretic behavior over time. A second, irreversible, mechanism is caused by corrosion of the silver metal top contact with the formation of silver iodide. These findings provide directions for the design of new and more stable perovskite/silicon tandems

Monolithic Perovskite‐Silicon Tandem Solar Cells: From the Lab to Fab?

“…[214] Ag oxidation was observed at both the front and rear sides of the textured monolithic perovskite-SHJ tandem solar cell after 250 h of stability testing (glass/ glass with edge sealant but no encapsulant, Figure 6a) and after 6 months in the field. [75,192] The Ag oxidation on the rear side of the tandem cell suggests that some iodide transport may have occurred in the form of volatile species during operation. Alternatively, metals may also diffuse into the absorber during operation and degrade it (Figure 6a).…”

“…And similarly to light and elevated temperature-induced degradation occurring in PERC cells, [231,232] operations in the field of the first perovskite(-silicon) tandem modules will certainly reveal additional degradation pathways not anticipated in the laboratory. [233,234] 6. Other Monolithic Tandem Cell Designs…”

“…While a degradation linked to the perovskite absorber was found to be reversible at night, the metal electrode irreversibly reacted with iodine, leading to a loss in FF from about 80% to 50%. [ 192 ] Although these preliminary results are encouraging, significant efforts are required to bring the stability of tandem solar cells to a level that is comparable to c‐Si bottom cells, which typically demonstrate 80% or more of their initial performance after 25 years in the field (corresponding to ≈50,000 h of sunlight).…”

A review on monolithic perovskite/c-Si tandem solar cells: progress, challenges, and opportunities

“…[136][137][138][139][140][141][142][143][144] For chemical stability, the encapsulation of PSK devices can effectively improve the tolerance to moisture and oxygen and avoid the causative factor of PSK crystal dissociation. [145][146][147][148][149][150] However, it has been an insurmountable problem for physical stability, because the lattice of PSK is not stable, temperature alone can induce phase changes, 151,152 and ion diffusion and migration occur all the time (e.g., the activation energy of I À for vacancy-assisted migration is only 0.6 eV 133 ). Moreover, several studies 138,143 have shown that ion migration may be one of the causes of lightinduced phase segregation in wide-bandgap mixed halide PSK, indicating that the physical dissociation factors are not independent but complementary.…”

“…136–144 For chemical stability, the encapsulation of PSK devices can effectively improve the tolerance to moisture and oxygen and avoid the causative factor of PSK crystal dissociation. 145–150 However, it has been an insurmountable problem for physical stability, because the lattice of PSK is not stable, temperature alone can induce phase changes, 151,152 and ion diffusion and migration occur all the time ( e.g. , the activation energy of I − for vacancy-assisted migration is only 0.6 eV 133 ).…”