A self-assembled bilayer could enhance the thermal stability of perovskite solar cells

Over the previous few years, photovoltaic (PV) applied sciences have turn into more and more widespread, contributing to the continuing quest to cut back greenhouse fuel emissions. Whereas most photo voltaic cells available on the market right now are made from silicon, different supplies are rising as promising alternate options for growing PV options.

Perovskites are amongst these supplies, as they could possibly be used to create extra reasonably priced photo voltaic cells that exhibit excessive energy conversion efficiencies. Regardless of their potential, perovskite photo voltaic cells (PSCs) usually are not as secure as their silicon counterparts and their efficiency tends to say no at excessive temperatures and underneath fluctuating environmental situations.

A characteristic of those solar cells that may contribute to their degradation over time is their reliance on hole-selective self-assembled monolayers (SAMs), molecular movies that assist to draw constructive cost carriers. These movies typically don’t adhere nicely to the cells’ floor and contribute to the thermal instability of PSCs.

Researchers at Xi’an Jiaotong College, Uppsala College and different institutes just lately designed a self-assembled bilayer movie that might overcome the constraints of typical SAMs. Their paper, published in Nature Vitalityreveals that this structured bi-layer molecular movie might adhere higher to PSCs, enhancing their thermal stability and total efficiency.

“The adoption of PSCs requires improved resistance to high temperatures and temperature variations,” wrote Bitao Dong, Mingyang Wei and their colleagues of their paper.

“Hole-selective SAMs have enabled progress in the performance of inverted PSCs, yet they may compromise temperature stability owing to desorption and weak interfacial contact. We developed a self-assembled bilayer by covalently interconnecting a phosphonic acid SAM with a triphenylamine upper layer.”

The brand new self-assembled bilayer designed by the researchers provides an higher layer to a traditional SAM based mostly on phosphonic acid. This higher layer, made from the natural compound triphenylamine, kinds covalent bonds with the SAM, producing a polymerized community.

“This polymerized network, formed through Friedel–Crafts alkylation, resisted thermal degradation up to 100 °C for 200 h,” wrote Dong, Wei and their colleagues. “The face-on-oriented upper layer exhibited adhesive contact with perovskites, leading to a 1.7-fold improvement in adhesion energy compared with the SAM–perovskite interface.”

Dong, Wei and their colleagues examined their self-assembled bilayer in a sequence of checks and located that it adheres higher to perovskite surfaces than generally employed mono-layer SAMs. Notably, the strategy used to supply the bi-layer movie can be versatile and might be utilized to numerous SAM-forming molecules and alkylating brokers.

The researchers additionally utilized their self-assembled bilayer to inverted PSCs to discover the way it affected their efficiency. Their findings have been very promising, as introducing these movies resulted in good power-conversion efficiencies whereas additionally limiting the cells’ lack of effectivity over time and boosting their stability at excessive temperatures.

“We reported power conversion efficiencies exceeding 26% for inverted PSCs,” wrote Dong, Wei and their colleagues. “The champion devices demonstrated less than 4% and 3% efficiency loss after 2,000 h damp heat exposure (85 °C and 85% relative humidity) and over 1,200 thermal cycles between −40 °C and 85 °C, respectively, meeting the temperature stability criteria outlined in the International Electrotechnical Commission 61215:2021 standards.”

Sooner or later, the strategy devised by this analysis group could possibly be used to create different self-assembled bilayer movies to enhance the steadiness of PSCs. Collectively, these efforts might assist to advance perovskite-based photovoltaics, which might contribute to their widespread adoption.

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