Li Sheng, Yang Xiaotian, Cheng Siyang, Yang Yujie, Li Hao, Zheng Zhuo, Li Mubai, Yu Qiuhan, Yuan Shengjun, Lin Qianqian, Wang Zhiping
School of Physics and Technology, Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education, School of Microelectronics, Wuhan University, Wuhan, China.
Wuhan Institute of Quantum Technology, Wuhan, China.
Nat Commun. 2025 Aug 29;16(1):8072. doi: 10.1038/s41467-025-63532-w.
All-perovskite tandem solar cells offer great promise for achieving low levelized cost of electricity, but their performance remains limited by insufficient near-infrared photon absorption in narrow bandgap tin-lead (Sn-Pb) subcells. Micron-thick Sn-Pb layers are essential for maximizing absorption, yet high-concentration precursor solutions often cause non-uniform crystallization, stoichiometric imbalance and limited carrier diffusion lengths. Here we identify the root cause of these limitations as the insufficient coordination of tin(II) iodide (SnI) in conventional dimethylformamide (DMF)/dimethyl sulfoxide (DMSO) binary solvent system at high precursor concentrations, resulting in Sn-rich colloids that nucleate detrimental Sn-rich phases in final films. To address this, we develop a ternary solvent system that fully coordinates with SnI, suppressing Sn-rich phases and enabling stoichiometric, micron-thick Sn-Pb films with carrier diffusion lengths of ~11 μm. The enhanced Sn-Pb absorber achieves efficiencies of 24.2% in single-junction cells and 29.3% in tandem devices, along with significantly improved long-term operational stability.
全钙钛矿叠层太阳能电池在实现低平准化度电成本方面具有巨大潜力，但其性能仍受窄带隙锡铅（Sn-Pb）子电池中近红外光子吸收不足的限制。微米厚的Sn-Pb层对于实现最大吸收至关重要，然而高浓度前驱体溶液常常会导致结晶不均匀、化学计量失衡以及载流子扩散长度受限。在此，我们确定这些限制的根本原因是在高前驱体浓度下，传统的二甲基甲酰胺（DMF）/二甲基亚砜（DMSO）二元溶剂体系中碘化亚锡（SnI）的配位不足，从而产生富锡胶体，这些胶体在最终薄膜中形成有害的富锡相。为解决这一问题，我们开发了一种三元溶剂体系，该体系能与SnI充分配位，抑制富锡相的形成，并能制备出化学计量比合适、厚度为微米级、载流子扩散长度约为11μm的Sn-Pb薄膜。这种性能增强的Sn-Pb吸收层在单结电池中的效率达到24.2%，在叠层器件中的效率达到29.3%，同时其长期运行稳定性也得到了显著提高。
