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<p>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<sub>2</sub>) 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<sub>2</sub>, 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.</p>

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Solvent engineering enables tin-lead perovskite films with long carrier diffusion lengths and reduced tin segregation

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年8月29日

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  • Sheng Li,
  • Xiaotian Yang,
  • Siyang Cheng,
  • Yujie Yang,
  • Hao Li,
  • Zhuo Zheng,
  • Mubai Li,
  • Qiuhan Yu,
  • Shengjun Yuan,
  • Qianqian Lin,
  • Zhiping Wang

摘要

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 (SnI2) 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 SnI2, 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.