We investigated the formation of photovoltaic (PV) devices using direct n-Si/MAPI (methylammonium lead tri-iodide) two-sided heterojunctions for the first time (as a possible alternative to two-terminal tandem devices) in which charge might be generated and collected from both the Si and MAPI. Test structures were used to establish that the n-Si/MAPI junction was photoactive and that spiro-OMeTAD acted as a “pinhole blocking” layer in n-Si/MAPI devices. Two-terminal “substrate” geometry devices comprising Al/n-Si/MAPI/spiro-OMeTAD/Au were fabricated and the effects of changing the thickness of the semitransparent gold electrode and the silicon resistivity were investigated. External quantum efficiency and capacitance–voltage measurements determined that the junction was one-sided in the silicon—and that the majority of the photocurrent was generated in the silicon, with there being a sharp cutoff in photoresponse above the MAPI bandgap. Construction of band diagrams indicated the presence of an upward valence band spike of up to 0.5 eV at the n-Si/MAPI interface that could impede carrier flow. Evidence for hole accumulation at this feature was seen in both Kelvin-probe transients and from unusual features in both current–voltage and capacitance–voltage measurements. The devices achieved a hysteresis-free best power conversion efficiency of 2.08%, VOC 0.46 V, JSC 11.77 mA/cm2, and FF 38.4%, demonstrating for the first time that it is possible to create a heterojunction PV device directly between the MAPI and n-Si. Further prospects for two-sided n-Si/MAPI heterojunctions are also discussed.

中文翻译：

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用于光伏应用的具有甲基铵碘化铅钙钛矿的直接硅异质结构

我们首次研究了使用直接 n-Si/MAPI（甲基铵三碘化铅）两侧异质结（作为两端串联器件的可能替代品）形成可能产生电荷的光伏 (PV) 器件并从 Si 和 MAPI 中收集。测试结构用于确定 n-Si/MAPI 结是光敏的，spiro-OMeTAD 在 n-Si/MAPI 器件中充当“针孔阻挡”层。制造了包含 Al/n-Si/MAPI/spiro-OMeTAD/Au 的两端“基板”几何器件，并研究了改变半透明金电极厚度和硅电阻率的影响。外部量子效率和电容电压测量确定结在硅中的一侧 - 并且大部分光电流是在硅中产生的，在 MAPI 带隙上方的光响应中有一个急剧的截止。能带图的构建表明，在 n-Si/MAPI 界面处存在高达 0.5 eV 的向上价带尖峰，这可能会阻碍载流子流动。在开尔文探针瞬变和电流-电压和电容-电压测量中的异常特征中都可以看到该特征处空穴积累的证据。这些器件实现了 2.08% 的无滞后最佳功率转换效率、VOC 0.46 V、JSC 11.77 mA/cm2 和 FF 38.4%，首次证明可以直接在 MAPI 和n-Si。