Yang Hyunwoo, Park Hyoungmin, Kim Bora, Park Cheolwoo, Jeong Seonghwa, Chae Weon-Sik, Kim Wooyul, Jeong Munseok, Ahn Tae Kyu, Shin Hyunjung
Department of Chemical and Biological Engineering, Sookmyung Women's University, Seoul 04310, Republic of Korea.
Korea Basic Science Institute, Daegu Center, Daegu 41566, Republic of Korea.
J Phys Chem Lett. 2021 Mar 25;12(11):2770-2779. doi: 10.1021/acs.jpclett.1c00335. Epub 2021 Mar 12.
Nickel oxides (NiO) as hole transport layers (HTLs) in inverted-type perovskite solar cells (PSCs) have been widely studied mainly because of their high stability under illumination. Increases in the power conversion efficiency (PCE) with NiO HTLs have been presented in numerous reports, although the photoluminescence (PL) quenching behavior does not coincide with the PCE increase. The dynamics of the charge carrier transport between the NiO HTLs and the organic-inorganic halide perovskite absorbers is not clearly understood yet and quite unusual, in contrast to organic/polymerics HTLs. We deposited NiO HTLs with precisely controlled thicknesses by atomic layer deposition (ALD) and studied their photovoltaic performances and hole transfer characteristics. Ground state bleaching (GSB) recovery was observed by ultrafast transient absorption spectroscopy (TAS), which suggested that backward hole injection occurred between the perovskites and NiO HTLs, so that the uncommon PL behaviors can be clearly explained. Backward hole injection from the NiO HTL to the perovskite absorber originated from their similar valence band (VB) energy positions. The thickness increase of the NiO HTLs induced VB sharing, which caused a red-shift of the photoinduced hole absorption spectrum in near-infrared (NIR) femtosecond TAS and a decrease in the PL intensity. Our studies on inorganic metal oxide transport layers, NiO in this work, with a thickness dependence and the comparison with organic layers provide a better understanding of the interfacial carrier dynamics in PSCs.
氧化镍（NiO）作为倒置型钙钛矿太阳能电池（PSC）中的空穴传输层（HTL），因其在光照下具有高稳定性而受到广泛研究。尽管光致发光（PL）猝灭行为与功率转换效率（PCE）的提高并不一致，但众多报告中均呈现了使用NiO空穴传输层时功率转换效率的提高。与有机/聚合物空穴传输层相比，NiO空穴传输层与有机-无机卤化物钙钛矿吸收体之间的电荷载流子传输动力学尚未得到清晰理解，且颇为不同寻常。我们通过原子层沉积（ALD）精确控制厚度来沉积NiO空穴传输层，并研究了它们的光伏性能和空穴转移特性。通过超快瞬态吸收光谱（TAS）观察到基态漂白（GSB）恢复，这表明在钙钛矿和NiO空穴传输层之间发生了反向空穴注入，从而可以清楚地解释这种不寻常的PL行为。从NiO空穴传输层到钙钛矿吸收体的反向空穴注入源于它们相似的价带（VB）能量位置。NiO空穴传输层厚度的增加导致价带共享，这在近红外（NIR）飞秒TAS中引起光致空穴吸收光谱的红移以及PL强度的降低。我们对无机金属氧化物传输层（本工作中的NiO）的厚度依赖性研究以及与有机层的比较，有助于更好地理解PSC中的界面载流子动力学。
