Enhancing Seebeck Effects by Using Excited States in Organic Semiconducting Polymer MEH-PPV Based on Multilayer Electrode/Polymer/Electrode Thin-Film Structure

Abstract

This article reports the experimental studies on using photoexcitation-generated excited states as a new approach to increase Seebeck coefficient as well as electrical conductivity in an organic semiconducting polymer MEH-PPV (poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene) with multilayer electrode/polymer/electrode thin-film architecture. Our experimental results show that a photoexcitation can lead to a large Seebeck coefficient of 305 μV/K in the ITO/MEH-PPV/Au device under the light intensity of 16 mW/cm2. Simultaneously, the electrical conductivity is increased to 8.2 × 10–5 S/cm from the dark conductivity of 3.6 × 10–6 S/cm. Clearly, using excited states can lead to a simultaneous increase on Seebeck coefficient and electrical conductivity, as compared to opposite phenomenon induced by doping: increasing electrical conductivity but decreasing Seebeck coefficient. Our experimental studies suggest that excited states can increase both the entropy difference between high and low-temperature surfaces through electron–phonon coupling and the charge density through dissociation to simultaneously enhance Seebeck coefficient and electrical conductivity in the ITO/MEH-PPV/Au device. The underlying mechanism can be attributed to the fact that excited states can largely affect the dominating electrical-transporting factor, namely, interchain electrical transport, but negligibly changes the dominating thermal-transporting factor, namely, interchain thermal transport in an organic semiconducting polymer. As a result, using photogenerated excited states presents a promising approach to develop high Seebeck effects in organic semiconducting materials based on multilayer electrode/polymer/electrode thin-film design.

Bismuth Doping–Induced Stable Seebeck Effect Based on MAPbI3 Polycrystalline Thin Films

“…In addition, we find the undoped perovskite thin film possesses negative Seebeck coefficient under 35 °C; when the temperature was increased from 35 to 70 °C, the Seebeck coefficient shows positive value. As perovskite plays a role of n‐type semiconductor as well of p‐type semiconductor, the controlling phase transition temperature acts as an effective way to modulate the electronic and thermoelectric properties . The Bi‐doped MAPbI 3 films exhibit positive Seebeck coefficient from 30 to 70 °C, which means the majority charge carrier of Bi‐doped MAPbI 3 carrier is hole.…”

“…At low temperature, the Seebeck voltage produced by thermally assisted charge transport mainly comes from entropy difference, but at high temperature, it comes simultaneously from entropy as well as polarization which is both beneficial for enhanced Seebeck coefficient and carrier transport. [16a,18]…”

Enhancement in thermoelectric properties using a P-type and N-type thin-film device structure

“…Figure shows the electrical conductivity and Seebeck coefficient generated from the ITO/P3HT/Au device under illumination, with PCBM doping content of 10%, 20%, 30%. We have previously researched the thermoelectric properties of single p‐type and n‐type thermoelectric devices under dark conditions and showed that the thermoelectric properties are better under illumination than in dark conditions. Therefore, here we have only studied the device thermoelectric properties under illumination conditions.…”

“…During the Seebeck measurements, the ITO substrate is heated, and the unheated side is cooled using a fan to maintain a constant temperature. In our previous research , we used the light intensity of 8, 12, 16 mW/cm 2 , and we knew that the Seebeck coefficient and electrical conductivity increased as the light intensity increased. To ensure consistent results here we selected light intensity of 16 mW/cm 2 using a filament lamp.…”

A Bowknot-like RuO2 quantum dots@V2O5 cathode with largely improved electrochemical performance

“…Thus, it is required to use V 2 O 5 in conjunction with another nanostructured material possessing higher electronic conductivity. [27][28][29][30] For example, Chen et al constructed the MWCNT-V 2 O 5 core-shell sponge for high power density. 31 Zhang et al fabricated carbon-coated V 2 O 5 with high performance.…”