# Enhancing the Power Output of InSe-Based Screen-Printed Flexible Thermoelectric Generators through a Bi–Te–Co-Doping Strategy

## TL;DR

Researchers improved the performance of flexible thermoelectric generators by using a new Bi/Te doping strategy in InSe materials, making them more efficient and durable.

## Contribution

The novel contribution is the use of Bi/Te co-doping in InSe to simultaneously enhance electrical and thermal properties while maintaining flexibility.

## Key findings

- Bi/Te co-doped InSe achieved a 6-fold increase in power output compared to undoped InSe.
- The material showed a high Seebeck coefficient of -452 μV/K and a voltage output of 47 mV.
- Devices maintained performance with minimal resistance variation under bending and 500 mechanical cycles.

## Abstract

The advancement of flexible thermoelectric generators
(FTEGs) is
hindered by the brittleness, rigidity, and complex processing of conventional
materials, as well as challenges in achieving both mechanical durability
and efficient charge transport. Although single-element doping, alloying,
and nanostructuring have been explored to enhance thermoelectric performance,
they often require complex synthesis or cause trade-offs between electrical
and thermal transport. Here, we show that Bi/Te codoping in indium
selenide (InSe) provides a more effective approach by simultaneously
optimizing carrier concentration and introducing phonon scattering
centers, thereby achieving balanced improvements in the Seebeck coefficient,
electrical conductivity, and thermal conductivity. Bi/Te codoped InSe
powders were synthesized via a conventional solid-state reaction method,
and flexible FTEGs were subsequently fabricated using a facile and
scalable screen-printing technique, providing a cost-effective and
industrially viable alternative. Structural analysis confirms the
formation of phase-pure hexagonal InSe, with enhanced crystallinity
achieved at an optimal 4% Bi doping level. Hall effect measurements
reveal that codoping significantly improves electrical properties,
resulting in a high Seebeck coefficient (-452 μV/K), increased
voltage output (47 mV), and superior power output (∼0.14 nW
at ΔT = 116 °C) for the In0.96Bi0.04Se0.97Te0.03 composition,
representing a 6-fold increase in power output compared to pristine
InSe. Moreover, the fabricated devices exhibit exceptional flexibility
and mechanical reliability, maintaining electrical performance with
∼5% resistance variation under bending and 500 mechanical cycles.
This work not only demonstrates a high-performing n-type InSe-based
flexible thermoelectric material but also establishes a practical
route toward scalable, wearable energy-harvesting devices.