Wenger Bernard, Nayak Pabitra K, Wen Xiaoming, Kesava Sameer V, Noel Nakita K, Snaith Henry J
Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, UK.
Australian Centre for Advanced Photovoltaics, University of New South Wales, Sydney, 2052, New South Wales, Australia.
Nat Commun. 2017 Sep 19;8(1):590. doi: 10.1038/s41467-017-00567-8.
Ultralow trap densities, exceptional optical and electronic properties have been reported for lead halide perovskites single crystals; however, ambiguities in basic properties, such as the band gap, and the electronic defect densities in the bulk and at the surface prevail. Here, we synthesize single crystals of methylammonium lead bromide (CHNHPbBr), characterise the optical absorption and photoluminescence and show that the optical properties of single crystals are almost identical to those of polycrystalline thin films. We observe significantly longer lifetimes and show that carrier diffusion plays a substantial role in the photoluminescence decay. Contrary to many reports, we determine that the trap density in CHNHPbBr perovskite single crystals is 10 cm only one order of magnitude lower than in the thin films. Our enhanced understanding of optical properties and recombination processes elucidates ambiguities in earlier reports, and highlights the discrepancies in the estimation of trap densities from electronic and optical methods.Metal halide perovskites for optoelectronic devices have been extensively studied in two forms: single-crystals or polycrystalline thin films. Using spectroscopic approaches, Wenger et al. show that polycrystalline thin films possess similar optoelectronic properties to single crystals.
据报道，卤化铅钙钛矿单晶具有超低陷阱密度、优异的光学和电子特性；然而，诸如带隙等基本性质以及体相和表面的电子缺陷密度仍存在模糊性。在此，我们合成了甲基溴化铅（CH₃NH₃PbBr₃）单晶，对其光吸收和光致发光进行了表征，并表明单晶的光学性质与多晶薄膜几乎相同。我们观察到寿命显著更长，并表明载流子扩散在光致发光衰减中起重要作用。与许多报道相反，我们确定CH₃NH₃PbBr₃钙钛矿单晶中的陷阱密度为10¹⁷cm⁻³，仅比薄膜中的低一个数量级。我们对光学性质和复合过程的深入理解澄清了早期报道中的模糊之处，并突出了从电学和光学方法估计陷阱密度时的差异。用于光电器件的金属卤化物钙钛矿主要以两种形式进行了广泛研究：单晶或多晶薄膜。Wenger等人使用光谱方法表明，多晶薄膜具有与单晶相似的光电性质。
