Researchers at the Nova University of Lisbon, University of Aveiro and University of York have created an ultra-thin perovskite solar cell with a checkerboard tile pattern that shields the perovskite layer from UV degradation. The design includes a luminescent down-shifting encapsulant, which enhances UV photon conversion and boosts overall efficiency.
The team provided background for this work, stating that advanced light management techniques can enhance the sunlight absorption of perovskite solar cells (PSCs). When located at the front, they may act as a UV barrier, which is paramount for protecting the perovskite layer against UV-enabled degradation. Although it was recently shown that photonic structures such as Escher-like patterns could approach the theoretical Lambertian-limit of light trapping, it remains challenging to also implement UV protection properties for these diffractive structures while maintaining broadband absorption gains.
“Through a combined optical and electrical modeling approach, this photonic structure can increase photocurrent and power conversion efficiency in ultrathin PSCs by 25.9% and 28.2% , respectively,” said the team in its work.
The study also showed that over 94% of incoming UV radiation can be efficiently converted into the visible spectrum.
The team’s research introduces a new approach to improve the performance, UV resistance, and flexibility of perovskite solar cells (PSCs). The team used a combination of two innovative techniques: a special checkerboard design for light trapping (LT) and a material that converts UV light into visible light.
Initially, the checkerboard design was intended to enhance light absorption within the solar cells. They then paired it with a sophisticated coating composed of a substance modified with lanthanide, which helps shield the cells from damage by converting UV rays into visible light.
Even in cases when light strikes the cells at varied angles, the checkerboard-shaped LT design increases photocurrent by 25.9%. The ultrathin solar cells exhibit a 28% boost in efficiency, reaching a projected power conversion efficiency (PCE) of 24.1% with only a 250 nm perovskite layer.
The researchers highlight that despite possible fabrication faults, these LT structures exhibit great resilience, with performance fluctuating relatively little.
Additionally, the LDS coating, made from new material (t-U (5000)/Eu3+), enhances the solar cells’ stability without lowering their performance. It reduces damaging UV effects by 94% and slightly improves light absorption in the perovskite layer.
While the LDS coating has a greater impact on simpler PSC designs, the combination of LT and LDS works best for space applications. This approach improves efficiency and stability under high UV exposure and increases the power-to-weight ratio of solar panels.
According to the researchers, by combining light trapping with luminescent downshifting layers, this work unravels a potential photonic solution to overcome UV degradation in PSCs while circumventing optical losses in ultrathin cells, thus improving both performance and stability.
