Passivation of 3D perovskite light-harvesting layers with 2D perovskites is an effective strategy to boost the stability, PCEs and reliability of perovskite solar cells. These 2D layers can protect the light-harvesting layers, reducing their reactivity to environmental factors and thus preventing them from degrading quickly over time.
Researchers from China's Wuhan University of Technology, Xidian University, University of Electronic Science and Technology of China and Germany's Technical University of Munich recently reported a strategy to prompt the formation of homogenous 2D perovskite passivation layers in perovskite-based solar cells. Using their proposed method, they achieved good active-area efficiencies and stabilities in perovskite solar modules based on formamidinium and cesium.
In their paper, the team stated: "The formation of a homogeneous passivation layer based on phase-pure two-dimensional (2D) perovskites is a challenge for perovskite solar cells, especially when upscaling the devices to modules". "We reveal a chain-length-dependent and halide-related phase separation problem of 2D perovskite growing on top of three-dimensional perovskites. We demonstrate that a homogeneous 2D perovskite passivation layer can be formed upon treatment of the perovskite layer with formamidinium bromide in long-chain ( >10) alkylamine ligand salts."
The researchers found that the homogenous 2D passivation layer formed using their proposed strategy produced a uniform, stable and high-quality 3D/2D heterostructure perovskite. This boosted both the efficiency and stability of the resulting perovskite solar cells, which varied slightly based on their size.
"We achieve champion active-area efficiencies of 25.61%, 24.62% and 23.60% for antisolvent-free processed small- (0.14 cm2) and large-size (1.04 cm2) devices and mini-modules (13.44 cm2), respectively," wrote the scientists.
"This passivation strategy is compatible with printing technology, enabling champion aperture-area efficiencies of 18.90% and 17.59% for fully slot-die printed large solar modules with areas of 310 cm2 and 802 cm2, respectively, demonstrating the feasibility of the upscaling manufacturing."
Notably, the team found that the formation of the 2D perovskite passivation layer also boosted the stability of solar cells. Mini-modules exhibited a remarkable operational stability, with a T80 lifetime exceeding 2,000 h at maximum power point tracking (MPPT) under continuous light illumination.
The strategy proposed by the researchers is also scalable and could be easy to implement on a large scale using existing printing technologies. In the future, it could help to accelerate the commercialization of more affordable solar modules based on perovskites.
