In a step towards sustainable alternatives to the conventional lead-based perovskite photovoltaics, researchers at the University of Queensland have developed a tin-halide perovskite (THP) cell, achieving 16.65% efficiency. 

 This lab-scale efficiency was achieved on a small-area substrate that utilizes materials that are not used in commercially available perovskite cell technology. The cell was based on one of several perovskite material types used in making solar cells: tin-based perovskites. 

The tin-based perovskites usually use organic-inorganic hybrid compositions of methylammonium (MA) or formamidinium (FA), such as MASnI3 or FASnI3, or other variants. 

 The use of tin is accompanied by challenges such as atmospheric oxidation and poor quality of perovskite films as a result of the rapid growth of the film (fast-crystalline behavior). This results in grain boundaries and potential defects, in addition to poor passivation. As a result of these challenges, achieving higher conversion efficiencies comparable to the lead-based perovskites has been the biggest hurdle for THP. 

The researchers at the University of Queensland claim to have used a colloidal chemistry involving cesium ions and were able to control the growth and enhance the quality of the THP film. 

Led by Professor Lianzhou Wang, the team further highlights that much work is still needed to optimize the production techniques for scalability and improve the durability of THP solar cells. 

The conventional lead-based perovskite cell technology has achieved efficiencies of over 25%, but the toxic nature of lead makes it environmentally unfriendly. The UQ research team promotes their lead-free solution for perovskite solar cells as a more eco-friendly alternative, while also broadening it to more versatile applications where lead cannot be used. 

“Our results using tin shows that we can offer a safer path forward - without the need for lead and without significantly compromising performance,” says Professor Wang.