Researchers from Guangdong University of Technology have developed a zinc-ion (Zn2+) modification strategy that improves both the efficiency and the stability of all-inorganic CsPbBr3 perovskite solar cells.
All-inorganic CsPbBr3 perovskites are known for their excellent environmental stability compared with hybrid organic-inorganic perovskites, since they avoid the organic cations (such as MA+ and FA+) that are prone to degrading under heat, moisture, oxygen and light. That stability comes at a cost, however: CsPbBr3's wide bandgap (about 2.3 eV) limits light harvesting, and its films typically suffer from low crystallinity and high defect density, which drive charge recombination and hold back power conversion efficiency (PCE).
The team's Zn2+ modification strategy is designed to address the film-quality side of that trade-off. Introducing Zn2+ optimizes the crystallization of the CsPbBr3 film, producing a denser, pinhole-free morphology with larger grain size and improved crystallinity. That microstructural improvement enhances light absorption and suppresses non-radiative recombination losses. The 0.5% Zn2+-modified device achieved a champion PCE of 8.54%, a 21% improvement over the 7.07% efficiency of the unmodified control device. The unencapsulated modified device also retained over 91.6% of its initial efficiency after 720 hours (30 days) of storage at 80°C and 80% relative humidity.
The researchers note that metal-ion doping has become a common strategy for improving CsPbBr3 PSCs, citing prior work using dopants such as Sm3+ (10.14% PCE), Sr2+ (9.63% PCE) and Sn2+ (efficiency raised from 6.85% to 8.63%). They point to zinc's low cost, natural abundance, low toxicity and stable +2 oxidation state as reasons for exploring it as a modifier, alongside evidence from other studies that moderate Zn2+ doping improves crystallinity and grain size in perovskite films.
