Pyrite FeS₂ has extraordinary potential as a low-cost, nontoxic, sustainable photovoltaic but has underperformed dramatically in prior solar cells. The latter devices focus on heterojunction designs, which are now understood to suffer from problems associated with FeS₂ surfaces. Simpler homojunction cells thus become appealing but have not been fabricated due to the historical inability to understand and control doping in pyrite. While recent advances have put S-vacancy and Co-based n-doping of FeS₂ on a firm footing, unequivocal evidence for bulk p-doping remains elusive. Here, we demonstrate the first unambiguous and controlled p-type transport in FeS₂ single crystals doped with phosphorus (P) during chemical vapor transport growth. P doping is found to be possible up to at least ∼100 ppm, inducing ∼10¹⁸ holes/cm³ at 300 K, while leaving the crystal structure and quality unchanged. As the P doping is increased in crystals natively n-doped with S vacancies, the majority carrier type inverts from n to p near ∼25 and ∼55 ppm P, as detected by Seebeck and Hall effects, respectively. Detailed temperature- and P-doping-dependent transport measurements establish that the P acceptor level is 175 ± 10 meV above the valence band maximum, explain details of the carrier inversion, elucidate the relative mobility of electrons and holes, reveal mid-gap defect levels, and unambiguously establish that the inversion to p-type occurs in the bulk and is not an artifact of hopping conduction. Such controlled bulk p-doping opens the door to pyrite p–n homojunctions, unveiling new opportunities for solar cells based on this extraordinary semiconductor.

中文翻译：

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黄铁矿 FeS2 的受控 p 型掺杂

黄铁矿 FeS ₂作为一种低成本、无毒、可持续的光伏材料具有非凡的潜力，但在现有太阳能电池中表现不佳。后一种器件侧重于异质结设计，现在认为异质结设计存在与 FeS ₂表面相关的问题。因此，更简单的同质结电池变得很有吸引力，但由于历史上无法理解和控制黄铁矿中的掺杂，因此尚未被制造出来。尽管最近的进展已使FeS ₂的S 空位和 Co 基n掺杂站稳脚跟，但体相p掺杂的明确证据仍然难以捉摸。_{在这里，我们展示了 FeS 2}中第一个明确且受控的p型传输在化学气相传输生长过程中掺杂磷 (P) 的单晶。发现 P 掺杂可能高达至少～100 ppm，在 300 K 下诱导～10 ^{18 个}孔/cm ³，同时保持晶体结构和质量不变。随着 P 掺杂在具有 S 空位的天然n掺杂晶体中增加，多数载流子类型从n反转为p分别由塞贝克和霍尔效应检测到~25 和~55 ppm P。详细的温度和 P 掺杂相关传输测量确定 P 受体能级比价带最大值高 175 ± 10 meV，解释载流子反转的细节，阐明电子和空穴的相对迁移率，揭示中间间隙缺陷水平, 并且明确地确定p型的反转发生在体积中并且不是跳跃传导的产物。这种受控的体p掺杂打开了黄铁矿p-n同质结的大门，为基于这种非凡半导体的太阳能电池揭示了新的机会。