(Invited) Semiconductor Nanocrystal Optoelectronics of Colloidal Quantum Wells

Abstract

Solution-processed semiconductor nanocrystals have been attracting increasingly greater interest in photonics including spectrally pure color conversion and enrichment in quality lighting and display backlighting [1,2]. These nanocrystals span different types and structures of semiconductors in the form of colloidal quantum dots and rods to a more recently developing class of colloidal quantum wells. In this talk, we will introduce the emergent field of nanocrystal optoelectronics using solution-processed quantum dots and wells. In particular, we will present a new concept of all-colloidal lasers developed by incorporating nanocrystal emitters as the optical gain media, intimately integrated into fully colloidal cavities [3]. In the talk, we will then focus on our recent work on the latest rising star of tightly-confined atomically flat nanocrystals, the quasi-2D colloidal quantum wells (CQWs), also popularly nick-named ‘nanoplatelets’. Among various extraordinary features of these CQWs, we will present our most recent discovery that the CQWs uniquely enable record high optical gain coefficients among all colloids [4]. In addition, we will show the controlled stacking and assemblies of these nanoplatelets, which provides us with the ability to tune and master their excitonic properties [5], and present the first accounts of doping them for high-flux solar concentration [6] and precise wavefunction-engineered magnetic properties [7]. Given their current accelerating progress, these solution-processed quantum materials hold great promise to challenge their epitaxial thin-film counterparts in semiconductor optoelectronics in the near future.[1] H. V. Demir et al., Nano Today 6, 632 (2011).[2] E. Mutlugün et al., Nano Letters 12, 3986 (2012); T. Özel et al., Nano Letters 13, 3065 (2013); X. Yang et al., ACS Nano 8, 8224 (2014).[3] B. Güzeltürk et al., Advanced Materials 27, 2741 (2015); and ACS Nano 8, 6599 (2014).[4] B. Güzeltürk et al., Nano Letters 19, 277 (2019).[5] O. Erdem et al., Nano Letters 19, 4297 (2019); N. Taghipour et al., ACS Nano 12, 8547 (2018).[6] M. Sharma et al., Advanced Materials 29, 1700821 (2017); M. Sharma et al., Chemistry of Materials 30, 3265 (2018).[7] F. Muckel et al., Nano Letters 18, 2047 (2018). Figure 1