Single-Crystal Perovskite Solar Cells Exhibit Close to Half A Millimeter Electron-Diffusion Length

摘要

Single-crystal halide perovskites exhibit photogenerated-carriers of high mobilityand long lifetime, making them excellent candidates for applications demandingthick semiconductors, such as ionizing radiation detectors, nuclear batteries,and concentrated photovoltaics. However, charge collection depreciates withincreasing thickness; therefore, tens to hundreds of volts of external bias isrequired to extract charges from a thick perovskite layer, leading to a considerableamount of dark current and fast degradation of perovskite absorbers. However,extending the carrier-diffusion length can mitigate many of the anticipatedissues preventing the practical utilization of perovskites in the abovementionedapplications. Here, single-crystal perovskite solar cells that are up to 400 timesthicker than state-of-the-art perovskite polycrystalline films are fabricated, yetretain high charge-collection efficiency in the absence of an external bias. Cellswith thicknesses of 110, 214, and 290 μm display power conversion efficiencies(PCEs) of 20.0, 18.4, and 14.7%, respectively. The remarkable persistence of highPCEs, despite the increase in thickness, is a result of a long electron-diffusionlength in those cells, which was estimated, from the thickness-dependent shortcircuitcurrent, to be ≈0.45 mm under 1 sun illumination. These results pave theway for adapting perovskite devices to optoelectronic applications in which athick active layer is essential.