Rodà Carmelita, Macias-Pinilla David F, Di Giacomo Alessio, Planelles Josep, Climente Juan I, Moreels Iwan
Department of Chemistry, Ghent University, 9000 Gent, Belgium.
Department de Química Física i Analítica, Universitat Juame I, Av. Sos Baynat s/n, 12071, Castelló, Spain.
Nano Lett. 2025 Sep 3;25(35):13251-13257. doi: 10.1021/acs.nanolett.5c03251. Epub 2025 Aug 19.
Optical amplification in CdSe nanoplatelets (NPLs) has been linked to biexcitons with a large binding energy Δ, preventing dissociation at room temperature. While the exciton binding energy Δ has been studied extensively, Δ in colloidal NPLs is typically inferred using the 2D Haynes rule, Δ = 0.228·Δ. Systematic studies of Δ in CdSe NPLs with varying thicknesses and lateral dimensions are still lacking. Here, we used transient absorption spectroscopy to investigate Δ, through photoinduced biexciton absorption. Δ ranges between 40 and 55 meV and increases by 30% when reducing the width from 9 to 3 nm, while overall 3.5 ML NPLs have only 10% higher Δ compared to 4.5 ML NPLs. Fitting the linear absorbance spectra, we extracted Δ and demonstrate that the Δ/Δ ratio is substantially lower than 0.228. Results confirm that biexcitons in CdSe NPLs are stable at room temperature and have an increased Δ in laterally confined NPLs.
硒化镉纳米片（NPLs）中的光学放大与具有大结合能Δ的双激子有关，这使得双激子在室温下不会解离。虽然激子结合能Δ已得到广泛研究，但胶体NPLs中的Δ通常是使用二维海恩斯规则Δ = 0.228·Δ推断得出的。对于不同厚度和横向尺寸的硒化镉NPLs中的Δ，仍缺乏系统性研究。在此，我们通过光致双激子吸收，利用瞬态吸收光谱来研究Δ。Δ的范围在40至55毫电子伏特之间，当宽度从9纳米减小到3纳米时，Δ增加30%，而总体而言，3.5单层的NPLs的Δ仅比4.5单层的NPLs高10%。通过拟合线性吸收光谱，我们提取了Δ，并证明Δ/Δ比值远低于0.228。结果证实，硒化镉NPLs中的双激子在室温下是稳定的，并且在横向受限的NPLs中Δ会增加。
