New Polymer Design Fortifies Perovskite Solar Cells Against Failure

Perovskite solar cells (PSCs) are the rising stars of photovoltaics, offering immense efficiency potential. However, they possess a significant vulnerability known as 'reverse bias instability'—a tendency to fail when voltage is reversed, which limits their long-term reliability. To address this, researchers investigated the hole transport layer (HTL), the critical component responsible for moving positive charges out of the cell.

Using electroluminescence mapping, the team discovered that standard HTLs often suffer from poor uniformity. These microscopic inconsistencies create weak spots where electrons can inadvertently inject into the layer, causing the device to break down. While previous materials like thick PTAA layers offered better protection, they unfortunately sacrificed efficiency and suffered from poor wettability.

The solution arrived in the form of a new polymeric material named Poly-PhPACz. This innovative layer combines high conductivity with excellent coverage, effectively blocking unwanted electron injection. When blade-coated in ambient conditions, the resulting cells achieved an impressive 26.1% efficiency and retained 92% of their performance after 1,800 hours of continuous light soaking. Crucially, further optimisation yielded a high breakdown voltage of -14.3 V without compromising energy output, paving the way for more robust and commercially viable solar technology.