Passivation technique reduces defects in kesterite solar cells to achieve 11.51% efficiency

Over the previous few many years, photo voltaic cells have develop into more and more widespread, with a rising variety of people and companies worldwide now counting on photo voltaic power to energy their properties or operations. Vitality engineers worldwide have thus been making an attempt to determine supplies which can be promising for the event of photovoltaics, are eco-friendly and non-toxic, and will also be simply sourced and processed.

These embody kesterite-based supplies, comparable to Cu₂ZnSnS₄ (CZTS), a category of semiconducting supplies with a crystal structure that resembles that of the naturally occurring mineral kesterite. Kesterite solar cells may have numerous benefits over the traditional silicon-based photovoltaics which can be most used as we speak, together with decrease manufacturing prices, a much less poisonous composition and larger flexibility.

Regardless of their potential, kesterite photo voltaic cells developed so far attain considerably decrease energy conversion efficiencies (PCEs) than their silicon counterparts. That is in nice half because of atomic-scale defects in kesterite-based supplies that entice cost carriers and immediate non-radiative recombination, a course of that causes power losses and thus reduces the photo voltaic cells’ efficiency.

Researchers at Shenzhen College and College of Rennes not too long ago launched a brand new passivation method that would assist to suppress defects in CZTS and different kesterites, which may in flip enhance the efficiency of photo voltaic cells primarily based on these supplies. Their proposed method, outlined in a paper published in Nature Vitalitywas discovered to end in photo voltaic cells with a licensed effectivity of 11.51%, with out the usage of any additional components to enhance the supplies’ properties.

“CZTS is a competitive photovoltaic material, especially for multijunction solar cells,” wrote Tong Wu, Shuo Chen and their colleagues of their paper. “However, the device power conversion efficiency has remained stagnant for years. Deep-level defects, such as sulfur vacancies (V_S), cause serious non-radiative recombination of charge carriers. We propose a passivation strategy for V_S through the heat treatment of the CdS/CZTS heterojunction in an oxygen-rich environment.”

The passivation technique devised by this workforce of researchers entails heating the CdS/CZTS heterojunction, which is the interface between the kesterite materials (i.e., CZTS) and a cadmium sulfide (CdS) buffer layerall inside an oxygen-rich setting. Buffer layers are intermediate layers in photo voltaic cells which can be positioned between absorber supplies, on this case CZTS, and a clear conductive materials.

“On this course of, V_S are occupied by oxygen atomssuppressing V_S defects,” defined Wu, Chen and their colleagues. “In addition, the diffusion of Cd ions to the CZTS absorber layer, and the formation of positive Na–O and Sn–O complexes can passivate related defects. These effects led to a reduced charge recombination and favorable band alignment.”

To reveal the potential of their passivation method, the researchers utilized it to actual CZTS-based photo voltaic cells after which assessed these cells’ efficiency in a sequence of checks. They discovered that their technique improved the cells’ PCEs, with out the usage of any components or extrinsic doping methods.

“We demonstrate a certified efficiency of 11.51% for air-solution-processed CZTS solar cells (bandgap of 1.5 eV) without any extrinsic cation alloying,” wrote Wu, Chen and their colleagues. “The study offers insights into defect passivation and performance improvement mechanism of kesterite solar cells.”

Sooner or later, the current examine by Wu, Chen and their colleagues and the brand new passivation technique they devised may very well be perfected additional and utilized to different kesterite-based photo voltaic cells. Ultimately, it may contribute to the development of those photo voltaic cells, which may in flip facilitate their real-world deployment.

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