Sulfide kesterite Cu₂ZnSnS₄ provides an attractive low-cost, environmentally benign and stable photovoltaic material, yet the record power conversion efficiency for such solar cells has been stagnant at around 9% for years. Severe non-radiative recombination within the heterojunction region is a major cause limiting voltage output and overall performance. Here we report a certified 11% efficiency Cu₂ZnSnS₄ solar cell with a high 730 mV open-circuit voltage using heat treatment to reduce heterojunction recombination. This heat treatment facilitates elemental inter-diffusion, directly inducing Cd atoms to occupy Zn or Cu lattice sites, and promotes Na accumulation accompanied by local Cu deficiency within the heterojunction region. Consequently, new phases are formed near the hetero-interface and more favourable conduction band alignment is obtained, contributing to reduced non-radiative recombination. Using this approach, we also demonstrate a certified centimetre-scale (1.11 cm²) 10% efficiency Cu₂ZnSnS₄ photovoltaic device; the first kesterite cell (including selenium-containing) of standard centimetre-size to exceed 10%.

硫化亚硫酸氢钙石Cu ₂ ZnSnS ₄提供了一种有吸引力的低成本，对环境无害且稳定的光伏材料，但是多年来这种太阳能电池的创纪录功率转换效率一直停滞在9％左右。异质结区内的严重非辐射复合是限制电压输出和整体性能的主要原因。在这里，我们报告经认证的11％效率Cu ₂ ZnSnS ₄具有较高730 mV开路电压的太阳能电池，通过热处理来减少异质结复合。这种热处理有利于元素相互扩散，直接诱导Cd原子占据Zn或Cu晶格位点，并促进Na积累，并在异质结区域内伴随局部Cu缺乏。因此，在异质界面附近形成新的相，并且获得了更有利的导带对准，从而有助于减少非辐射复合。使用这种方法，我们还演示了认证的厘米级（1.11 cm ²）10％效率的Cu ₂ ZnSnS ₄光电器件；第一个标准厘米大小的钾钛矿电池（包括含硒）超过10％。