Simultaneously achieving high voltage and high efficiency in thin-film solar cells is of paramount importance for real-world applications. While solar cells fabricated from the Earth-abundant kesterite absorber Cu₂ZnSn(S _x Se_1−x )₄ provide an attractive, non-toxic, energy harvesting solution, their utilization has been constrained by relatively low open-circuit voltages that limit efficiency. Increasing the sulfur content to widen the bandgap boosts the voltage, but usually at the expense of efficiency. Here, we report important progress on this fundamental problem by fabricating solar cells with high sulfur content that exhibit efficiencies up to 11.89% with open-circuit voltages as high as 670 mV. In a multistep process, fully functional solar cells are separated from their growth substrate, and a high-work-function back contact is subsequently deposited. With this approach, we fabricated a series-connected device that produces 5.7 V under 1 Sun illumination and ~2 V under low lighting conditions, below 10⁻³ Suns.

同时在薄膜太阳能电池中实现高电压和高效率对于实际应用至关重要。而由富含地球的钾长石吸收体Cu ₂ ZnSn（S _x Se _{1- x}）₄制成的太阳能电池 由于提供了一种有吸引力的，无毒的能量收集解决方案，其使用受到了相对较低的开路电压的限制，从而限制了效率。增加硫含量以扩大带隙会提高电压，但通常会以效率为代价。在这里，我们报告了通过制造高硫含量的太阳能电池在此基本问题上的重要进展，该太阳能电池的开路电压高达670 mV，效率高达11.89％。在多步骤过程中，将功能齐全的太阳能电池与其生长衬底分离，然后沉积高功函数的背接触。通过这种方法，我们制造了一个串联连接的设备，该设备在1个太阳光照射下可产生5.7 V的电压，而在低于10 ^-3太阳的低光照条件下可产生约2 V的电压。