Compared with their three-dimensional (3D) counterparts, low-dimensional metal halide perovskites (2D and quasi-2D; B₂A_n−1M_nX_3n+1, such as B = R-NH₃⁺, A = HC(NH₂)₂⁺, Cs⁺; M = Pb²⁺, Sn²⁺; X = Cl⁻, Br⁻, I⁻) with periodic inorganic–organic structures have shown promising stability and hysteresis-free electrical performance^1,2,3,4,5,6. However, their unique multiple-quantum-well structure limits the device efficiencies because of the grain boundaries and randomly oriented quantum wells in polycrystals⁷. In single crystals, the carrier transport through the thickness direction is hindered by the layered insulating organic spacers⁸. Furthermore, the strong quantum confinement from the organic spacers limits the generation and transport of free carriers^9,10. Also, lead-free metal halide perovskites have been developed but their device performance is limited by their low crystallinity and structural instability¹¹. Here we report a low-dimensional metal halide perovskite BA₂MA_n−1Sn_nI_3n+1 (BA, butylammonium; MA, methylammonium; n = 1, 3, 5) superlattice by chemical epitaxy. The inorganic slabs are aligned vertical to the substrate and interconnected in a criss-cross 2D network parallel to the substrate, leading to efficient carrier transport in three dimensions. A lattice-mismatched substrate compresses the organic spacers, which weakens the quantum confinement. The performance of a superlattice solar cell has been certified under the quasi-steady state, showing a stable 12.36% photoelectric conversion efficiency. Moreover, an intraband exciton relaxation process may have yielded an unusually high open-circuit voltage (V_OC).

与它们的三维（3D）对应物相比，低维金属卤化物钙钛矿（2D和准2D；B ₂ A _{n -1} M _n X _{3 n +1}，例如B = R-NH ₃ ⁺，A =具有周期性无机-有机结构的HC(NH ₂ ) ₂ ⁺ , Cs ⁺ ; M = Pb ²⁺ , Sn ²⁺ ; X = Cl ^- , Br ^- , I ^{- ) 具有良好的稳定性和无滞后的电气性能1, 2,3,4,5,6}. ^{然而，由于多晶7}中的晶界和随机取向的量子阱，它们独特的多量子阱结构限制了器件的效率。在单晶中，载流子沿厚度方向的传输受到层状绝缘有机间隔物⁸的阻碍。此外，有机间隔物的强量子限制限制了自由载流子^9,10的产生和传输。此外，已开发出无铅金属卤化物钙钛矿，但其器件性能受到其低结晶度和结构不稳定性¹¹的限制。在这里，我们报告了一种低维金属卤化物钙钛矿 BA ₂ MA _{n -1} Sn _nI _{3 n +1} (BA, 丁基铵; MA, 甲基铵; n  = 1, 3, 5) 通过化学外延形成超晶格。无机板垂直于基板排列，并在平行于基板的纵横交错的二维网络中相互连接，从而在三个维度上实现高效的载流子传输。晶格不匹配的衬底压缩了有机间隔物，从而削弱了量子限制。超晶格太阳能电池在准稳态下的性能得到了验证，显示出稳定的12.36%的光电转换效率。此外，带内激子弛豫过程可能会产生异常高的开路电压 ( V _OC )。