Enhancement of thermoelectric performance of n -type AgBi 1+x Se 2 via improvement of the carrier mobility by modulation
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Bull Mater Sci (2020)43:315 https://doi.org/10.1007/s12034-020-02285-2
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Enhancement of thermoelectric performance of n-type AgBi1+xSe2 via improvement of the carrier mobility by modulation doping EKASHMI RATHORE , SATYA N GUIN and KANISHKA BISWAS* New Chemistry Unit, School of Advanced Materials and International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064, India *Author for correspondence ([email protected]) MS received 20 February 2020; accepted 13 July 2020 Abstract. High charge carrier mobility with low lattice thermal conductivity is one of the key factors for the design of a good thermoelectric material. Recent studies show that n-type Te-free AgBiSe2 is promising compound for thermoelectric energy conversion due to intrinsically low lattice thermal conductivity. However, low charge carrier mobility in AgBiSe2 is the constraint for enhancement of its power factor. In the present study, we use a chemical modification way to realize modulation doping in AgBiSe2. The addition of 2–6 mol% excess Bi in AgBiSe2 results in the formation of Bi-rich modulation-doped microstructures of topological semimetal, Bi4Se3 in AgBiSe2 matrix. We show that due to facile carrier transport via semi-metallic Bi4Se3 microstructure results in overall improvement of carrier mobility without compromising Seebeck coefficient in AgBiSe2 system, which in turn results in a remarkable improvement in the power factor (rS2) value. A highest rS2 value of *6.35 lW cm-1 K-2 at 800 K has been achieved in AgBiSe2-3% Bi excess sample, which is higher than previously reported metal ion and halogen-doped AgBiSe2. Keywords.
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Thermoelectrics; modulation doping; mobility; power factor; thermal conductivity.
Introduction
In the recent years, the energy and environment related concern intensified the research in the arena of efficient, cost-effective and pollution-free means of power generation. Thermoelectric materials are the all solid-state converters without any moving part, can directly and reversibly convert waste heat into electricity [1–4]. Over the last two decades, there has been an escalated interest in the field of thermoelectric materials research. The effectiveness of a thermoelectric material is governed by the thermoelectric figure of merit, zT = rS2T/j, where r is the electrical conductivity, S is the Seebeck coefficient, T is the temperature in Kelvin and j is the thermal conductivity [1–4]. The fundamental challenge to design a promising thermoelectric material is intriguing due to conflicting thermoelectric parameters. To improve the thermoelectric properties, different concepts have been employed via improvement of the Seebeck coefficient or reduction of the thermal conductivity or by simultaneous tailoring of both the parameters. The
These authors contributed equally to this study.
This article is part of the Topical Collection: SAMat Focus Issue.
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