| Work Detail |
The proposed bilayer is used as a hole contact material that ensures an improved adhesive contact with the perovskite film. It consists of a phosphonic acid self-assembled monolayer with an upper layer made of an organic compound known as triphenylamine. Scientists at Xi’an Jiaotong University have fabricated an inverted perovskite solar cell that utilizes a self-assembled bilayer (SAB) as a hole-selective molecular contact. Inverted perovskite cells have a device structure known as “p-i-n”, in which hole-selective contact p is at the bottom of intrinsic perovskite layer “i” with electron transport layer n at the top. Conventional halide perovskite cells have the same structure but reversed – an “n-i-p” layout. In an n-i-p architecture, the solar cell is illuminated through the electron-transport layer (ETL) side; in the p-i-n structure, it is illuminated through the hole transport (HTL) surface. The proposed SAB consists of a phosphonic acid self-assembled monolayer (SAM) with an upper layer made of an organic compound known as triphenylamine, which is intended to improve the adhesive contact with the perovskite film compared with a conventional SAM-perovskite interface. It also enhances the interfaces thermal and mechanical robustness. “SABs represent a basic form of self-assembled multilayers, consisting of distinct monolayers with varying constituents—interconnected via covalent or ionic bonds,” the researchers explained. “This layer-by-layer assembly stabilizes the labile monolayer by introducing rigid components and enables control over film termination.” The team built the cell with a substrate made of glass and transparent conductive oxides (TCOs), the proposed bilayer, the perovskite absorber, an ETL based on buckminsterfullerene (C60), a bathocuproine (BCP) buffer layer, and a silver (Ag) metal contact. The cell was tested under standard illumination conditions and was found to achieve a power conversion efficiency of 26.04%, an open-circuit voltage of 1.185?V, a short-circuit current density of 26.27?mA?cm2, and a fill factor of 83.84% The cell was also able to retain around 94% of its initial efficiency after 2,000?h of damp heat testing at 85?C. “Notably, the best SAB device demonstrated a relative efficiency loss of less than 4% over 2,000?h, which is in line with the industry benchmark of a 5% loss over 1,000?h for silicon photovoltaics,” the academics said, noting that the result, which was certified by the China National Accreditation Service, is among the most efficient inverted perovskite devices ever built to date. The details of the cell technology can be found in the paper “Self-assembled bilayer for perovskite solar cells with improved tolerance against thermal stresses,” published in nature energy. |
