Ph.D. Thesis Colloquium
Name: Poulomi Mukherjee
Research Supervisor: Prof. D. D. Sarma
Title: Understanding the Energy-Transfer Pathways Culminating in Photoluminescence from Doped and Undoped Lead Halide Perovskites and Related Systems
Date and Time: Thursday, 7th May 2026 at 4:00 pm
Venue: Rajarshi Bhattacharya Memorial Lecture Hall, Chemical Sciences Building
Abstract:
The quest for materials exhibiting efficient photoluminescence (PL), along with the fundamental understanding of their emission characteristics, is of paramount importance for various optoelectronic and photonic applications. In this context, lead halide perovskites have emerged as a promising class of materials due to their remarkable defect tolerance, low-cost synthesis, strong absorption coefficient, tunable emission, and high photoluminescence quantum yield (PLQY).1–3 However, like conventional semiconductor nanocrystals, they often suffer from self-absorption losses due to the close energetic overlap between absorption and emission, which reduces their quantum efficiency. To overcome this limitation, dopant emission has been explored as an effective strategy, which enables large Stokes-shifted dopant emission, suppressing self-absorption via host-to-dopant excitation transfer.4,5 Despite extensive studies on dopant-induced emission across diverse host-dopant systems, the fate of this excess energy associated with the large Stokes shift of dopant emission relative to the host band gap and, consequently, the energy transfer pathways from the host to the dopant remain unknown. Therefore, the nature of dopant emission is unpredictable across different host-dopant combinations, and material design largely relies on empirical trial-and-error approaches.
Leveraging the outstanding optical properties of lead halide perovskites, this thesis addresses these challenges by establishing a framework for emission processes across a diverse set of lead halide perovskites and related compounds. The framework explicitly incorporates intrinsic host emission pathways, host-dopant coupling, and associated de-excitation pathways in the dopant. Using Mn2+-doped CsPbCl3 nanocrystals, we develop the foundational framework and resolve the long-standing question regarding the fate of excess energy associated with host-to-dopant excitation transfer.6 Subsequently, we extend this understanding of Mn2+ emission pathways across different compositions7 and dimensionality.8,9 This framework is further generalized to aliovalent Yb3+ doping, and we present mechanistic insights into the exceptional quantum cutting phenomena in Yb3+-doped CsPbCl3 nanocrystals.10 Beyond understanding dopant emission, the framework developed in this thesis also enables the determination of intrinsic host material properties, such as the electron–hole Coulomb interaction strength, quantified by the exciton binding energy, as well as defect-assisted recombination pathways, which are important parameters to determine the photovoltaic performance of a material. Accordingly, we develop a robust and simple method for determining exciton binding energies from temperature-dependent PL measurements,11 demonstrating the broader applicability of the developed framework.
References:
- L. Protesescu et al., Nano Lett. 15, 3692–3696 (2015).
- J. S. Manser et al., Chem. Rev. 116, 12956–13008 (2016).
- M. D. Smith et al., Chem. Rev. 119, 3104–3139 (2019).
- D. Parobek et al., Nano Lett. 16, 7376–7380 (2016).
- X. Yuan et al., Chem. Mater. 29, 8003–8011 (2017).
- P. Mukherjee et al., ACS Energy Lett. 10, 6381–6389 (2025).
- P. Mukherjee et al., (manuscript to be submitted).
- P. Mukherjee et al., (manuscript under review).
- P. Mukherjee et al., (manuscript to be submitted).
- P. Mukherjee & D. D. Sarma, Small (2026) doi:10.1002/smll.202514834.
- P. Mukherjee et al., (manuscript under preparation).