A strategy to enhance the stability of perovskite solar cells under reverse bias conditions

If a person photo voltaic cell is shaded and different cells in the identical module aren’t, the sunlit cells can attempt to drive present by means of the shaded cell, leading to a rise in temperature and potential harm to the cells. These situations put the shadowed cell beneath a situation often called reverse bias, which makes photo voltaic cells unstable and deteriorates their efficiency over time.

Researchers at College of North Carolina at Chapel Hill not too long ago launched a brand new technique that would enhance the steadiness of perovskite solar cells (PSCs) beneath reverse bias situations. This technique, outlined in a paper published in Nature Vitalitymight facilitate the longer term deployment of perovskite-based photovoltaics (PVs) in real-world settings.

“The reverse bias stability or shading induced instability of solar cells drew the attention of the PV community only recently,” Jinsong Huang, corresponding writer of the paper, advised Tech Xplore. “The shaded cells are subjected to the large reverse bias imposed by the rest of cells which are not shaded. For PSCs, the reverse bias-induced instability was reported to be much more severe in the past.”

Perovskite cells are identified to have a considerably thinner photoactive layer than different current PVs. In consequence, the electric field induced by reverse bias situations could be far bigger in such a cell.

“The notorious ion migration in perovskites also makes them much less stable under reverse bias,” Huang stated. “In most prior studies, PSCs were reported to break down or degrade after a few seconds to a few minutes under reverse bias of a few volts. If this problem is not solved, future perovskite modules will need many bypass diodes to protect them, pushing up their fabrication costs.”

When reviewing earlier literature, Huang and his colleagues noticed that some PSCs had been considerably extra steady beneath reverse bias situations. This motivated them to analyze the mechanisms underpinning this larger stability, within the hope of devising an efficient technique to stabilize perovskite cells.

“Degradation under reverse bias is complicated, as it varied with bias voltage, duration, perovskite quality and device stacking,” Huang defined. “In this study, we chose p-i-n structured PSCs as they have shown good operational stability from our previous studies. We used our optimized perovskite composition to minimize other possible degradation pathways.”

Huang and his colleagues utilized varied reverse bias values to PSCs, whereas altering the gadget stacks. They then intently examined what occurred within the units and tried to find out whether or not the phenomena they noticed had been correlated to the gadget’s efficiency.

“By doing this, we were able to identify the degradation mechanism inside the devices,” Huang stated. “We carefully distinguished the degradation behavior with breakdown and gradual degradation. The former happens under high reverse bias in a short period, while the latter happens under low reverse bias in a longer duration.”

The experiments carried out by Huang and his colleagues yielded fascinating outcomes. Particularly, they unveiled a collection of electrochemical reactions that had been related to the degradation of PSCs beneath reverse bias situations.

These reactions entailed the technology of iodine, which led to the corrosion of the Cu electrode within the cells. This course of, in flip, triggered the breakdown and degradation of the photo voltaic cells.

“Inspired by what we learned, we used a device stacking of lithium fluoride/tin oxide/indium tin oxidewhich also makes devices stable under light and heat, to inhibit the iodine formation under reverse bias the electrode corrosion,” Huang stated. “By doing so, the lifetime of modified PSCs could last up to 1,000 hours under reverse bias of -1.6 V. Such a good performance really surprised me, as up to one year ago I would never have thought they could be so stable.”

The findings gathered by this workforce of researchers might quickly inform the event of extra steady perovskite-based PVs, which might contribute to their future large-scale commercialization. Now that their analysis venture is full, Huang and his colleagues hope to conduct extra research, which might be geared toward delineating the higher restrict of the reverse bias stability for PSCs.

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