To further processes in stabilization for layers in perovskite optoelectronic devices, researchers at NREL have discovered a novel technique that generates a high-quality Al-doped zinc oxide electron transport layer which has reduced sheet resistance and also protects the underlying perovskite layer from both the ambient environment and from further device processing by, for example, a subsequently-deposited second perovskite absorber layer in a perovskite/perovskite tandem photovoltaic device.
The process involves the incorporation of an interfacial nucleation layer made of poly(ethylenimine) ethoxylated (PEIE) deposited on a C60 layer grown adjacent to a perovskite absorber layer. A subsequent metal oxide film of Al-doped zinc oxide (AZO) may then be grown upon the C60 layer with the assistance of the PEIE nucleation layer via atomic layer deposition (ALD); previously, growth of AZO on C60 has proven challenging, if not impossible. Measurements have shown that, with the assistance of PEIE, the AZO is deposited with a high degree of conformality, which protects the underlying layers from damage due to solvent exposure and is especially relevant for manufacturing perovskite-perovskite tandem solar cells. While the nucleation layer simultaneously provides stability improvements to layer adhesion, delamination prevention, and protection from ambient humidity or oxidizing conditions, the same encapsulation enables electrical current to flow out of the solar cell for photovoltaic operation with high performance.
This technology is within the Film Stability and Hole and Electron Extraction Layer Engineering groups of NREL’s perovskite portfolio. For further information regarding NREL's broader perovskite portfolio, please visit NREL's Perovskite Patent Portfolio website or contact Bill Hadley at: