A low-temperature strategy to prepare CuInS2 solar cells with efficiency exceeding 12%

Copper indium sulfide (CuInS 2 ) is a promising absorber among emerging chalcogenide photovoltaics. However, solution-processed CuInS 2 solar cells at low temperature (< 400°C) still lag far behind the requirement of at least 10% efficiency for practical application since 1993. Here, a low-temperature strategy, featuring a solution-processed In-rich CuInS 2 film interdigitated with electron-extracting interfaces and a sulfur anion-induced gradient phase transformation (S 2− -GPT) process at < 200°C, is conceptually developed for preparing the CuInS 2 solar cells with a breakthrough efficiency up to 12.28%. The interdigitated structure has unique advantages over the simple bilayer structure conventionally used; moreover, the S 2− -GPT process leads to the transformation from CuAu to CuIn 5 S 8 phase to reduce the defect density and charge recombination inside CuInS 2 film for boosting solar cell performance. The detailed principles behind material and device are elucidated. Our findings offer a promising way to chalcogenide solar cells and the application of CuInS 2 devices.