The conversion efficiency of ultra-thin solar cells based on layered materials has been limited by their open-circuit voltage, which is typically pinned to a value under 0.6 V. Here we report an open-circuit voltage of 1.02 V in a 120 nm-thick vertically stacked homojunction fabricated with substitutionally doped MoS₂. This high open-circuit voltage is consistent with the band alignment in the MoS₂ homojunction, which is more favourable than in widely-used TMDC heterostructures. It is also attributed to the high performance of the substitutionally doped MoS₂, in particular the p-type material doped with Nb, which is demonstrated by the observation of electroluminescence from tunnelling graphene/BN/MoS₂ structures in spite of the indirect nature of bulk MoS₂. We find that illuminating the TMDC/metal contacts decreases the measured open-circuit voltage in MoS₂ van der Waals homojunctions because they are photoactive, which points to the need of developing low-resistance, ohmic contacts to doped MoS₂ in order to achieve high efficiency in practical devices. The high open-circuit voltage demonstrated here confirms the potential of layered transition-metal dichalcogenides for the development of highly efficient, ultra-thin solar cells.

基于分层材料的超薄太阳能电池的转换效率受到其开路电压的限制，该开路电压通常固定为0.6 V以下的值。在这里，我们报道在120 nm的开路电压下为1.02 V用替代掺杂的MoS ₂制成的厚的垂直堆叠同质结。这种高的开路电压与MoS ₂同质结中的能带排列一致，这比在广泛使用的TMDC异质结构中更有利。这也归因于取代掺杂的MoS _2的高性能，特别是掺杂Nb的p型材料的性能，这可以通过观察隧穿石墨烯/ BN / MoS ₂的电致发光来证明。尽管有大量的MoS ₂的间接性质，但其结构却不相同。我们发现，照亮TMDC /金属触点会降低MoS ₂范德华同质结中测得的开路电压，因为它们是光敏的，这表明需要为掺杂的MoS ₂开发低电阻的欧姆触点以实现高的接触实际设备的效率。此处显示的高开路电压证实了层状过渡金属二硫化氢在开发高效超薄太阳能电池方面的潜力。