Semiconductor colloidal nanocrystals (NCs) can interact with each other to profoundly influence the charge transfer, transport and extraction processes after they have been assembled into a high-density film for optoelectronic device applications. These interactions normally occur among several nearby single colloidal NCs, which should be effectively separated from their surroundings to remove the ensemble average effect for fine optical characterizations. By means of atomic force microscopy (AFM) nanoxerography, here we prepare individual clusters of perovskite CsPbBr₃ NCs and perform single-particle measurements on their optical properties at the cryogenic temperature. While discrete photoluminescence bands can be resolved from the several single CsPbBr₃ NCs that are contained within an individual cluster, the shorter- and longer-wavelength bands are dramatically different in that their intensities show sub- and superlinear dependences on the laser excitation powers, respectively. This can be explained by the generation of charged excitons (trions) at high laser excitation powers, and their subsequent Dexter-type energy transfer from smaller- to larger-sized CsPbBr₃ NCs. Our findings not only suggest that these individual clusters prepared by AFM nanoxerography can serve as a potent platform to explore few-NC interactions but they also reveal the long-neglected role played by trions in channeling photo-excited energies among neighboring NCs.

半导体胶体纳米晶体 (NC) 在组装成用于光电器件应用的高密度薄膜后，可以相互作用，从而深刻影响电荷转移、传输和提取过程。这些相互作用通常发生在几个附近的单个胶体 NC 之间，它们应该有效地与其周围环境分离，以消除精细光学表征的整体平均效应。通过原子力显微镜 (AFM) 纳米静电复印术，我们在这里制备了钙钛矿 CsPbBr ₃ NCs 的单个簇，并在低温下对其光学特性进行单粒子测量。而离散的光致发光带可以从几个单一的 CsPbBr ₃包含在单个簇中的 NC，较短和较长波长的波段存在显着差异，因为它们的强度分别显示出对激光激发功率的亚线性和超线性依赖性。这可以通过在高激光激发功率下产生带电激子 (trions) 以及它们随后的 Dexter 型能量从较小尺寸的 CsPbBr 3 NCs 转移到较大尺寸的 CsPbBr ₃ NCs 来解释。我们的研究结果不仅表明通过 AFM 纳米静电复印法制备的这些单个簇可以作为探索少数 NC 相互作用的有效平台，而且它们还揭示了 trion 在相邻 NC 之间引导光激发能量方面长期被忽视的作用。