Harvesting Delayed Fluorescence in Perovskite Nanocrystals Using Vibrationally Assisted Delayed Fluorescence (VADF)
Pradeep KR a, Ranjani Viswanatha a
a JNCASR Jawaharlal Nerhu Centre for Advanced Scientific Research, Jakkur, BENGALURU, India
Online Conference
Proceedings of Online Conference on Perovskites for Energy Harvesting: From Fundamentals to Devices (PERENHAR)
Online, Spain, 2020 November 19th - 20th
Organizers: Dinesh Kabra, Sandheep Ravishankar, Angshuman Nag and Priya Mahadevan
Poster, Pradeep KR, 060
Publication date: 2nd November 2020
ePoster: 

 Nanoscale materials have been investigated extensively for energy-based applications like lighting and photovoltaics. In an era that is driven by the quest for energy efficiency, useful harvesting of any kind of losses is extremely important.  In this work, we have addressed one such aspect of reduction of non-radiative losses by using an impurity driven state to create an electron storehouse within the solid.  Here, we introduce the concept of drip feeding of photo-excited electrons from an impurity-induced spin-forbidden state leading to Vibrationally Assisted Delayed Fluorescence (VADF) to address the major shortcoming of surface trapping.  Electron detrapping from Mn2+ to the host conduction band through VADF is observed for the first time in a prototypical example of Mn-doped CsPbX3 (X = Cl, Br) nanocrystals. This has given rise to about 100% increase in the energy efficiency proving the need for these pathways. While this pathway has been enunciated using Mn as a dopant, this mechanism can be extended to all unsatisfied spin dopants like Ni, Co, Cu among many other materials with varying lifetimes and thus creating a new class of materials. Additionally, in the process of achieving this, we have possibly further enhanced the functionality by the use of spin-selective mechanism. Although traditionally magnetism has been used to address the magnetic properties, new materials with magnetic properties addressable via alternative means (for example, electrical or optical) may lead to improved flexibility and storage density and are therefore very desirable. The use of this mechanism ensures an optical control on spin, providing a stepping stone for room temperature photomagnetic materials.

References

K.R.Pradeep, D.Acharya, P.Jain, K.Gahlot, A.Yadav, A.Camellini, M.Zavelani-Rossi, G.Cerullo, C.Narayana, S.Narasimhan and R.Viswanatha, ACS Energy Lett.  5, 353-359 (2020).

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