Solar Harvesting: a Unique Opportunity for Organic Thermoelectrics?

Abstract

Thermoelectrics have emerged as a strategy for solar‐to‐electricity conversion, as they can complement photovoltaic devices as IR harvesters or operate as stand‐alone systems often under strong light and heat concentration. Inspired by the recent success of inorganic‐based solar thermoelectric generators (STEGs), in this manuscript, the potential of benchmark organic thermoelectric materials for solar harvesting is evaluated. It is shown that the inherent properties of organic semiconductors allow the possibility of fabricating organic STEGs (SOTEGs) of extraordinary simplicity. The broadband light absorption exhibited by most organic thermoelectrics combined with their low thermal conductivities results in a significant temperature rise upon illumination as seen by IR thermography. Under 2 sun illumination, a temperature difference of 50 K establishes between the illuminated and the non‐illuminated sides of a poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) film, and ≈40 K for a carbon nanotube/cellulose composite. Moreover, when using light as a heat source, the Seebeck coefficient remains unaffected, while a small photoconductivity effect is observed in PEDOT:PSS and carbon nanotubes. Then, the effect of several geometrical factors on the power output of a solar organic thermoelectric generator is investigated, enabling us to propose simple SOTEG geometries that capitalize on the planar geometry typical of solution‐processable materials. Finally, a proof‐of‐concept SOTEG is demonstrated, generating 180 nW under 2 suns.

Thermoelectric effect and devices on IVA and VA Xenes

“…For example, low-dimensional material-based photothermoelectric (PTE) detectors have successfully F I G U R E 7 Schematic of (A) graphene photothermoelectric detector device fabrication and principle of operation, Copyright 2018, Springer Nature (B) dual-output sensors based on thermoelectric effects monitoring fluid temperature and dynamics, Copyright 2018, Elsevier Ltd. All rights reserved. (C) Photo-Seebeck system under experiment (D) possible device architectures of SOTEGs, Copyright 2014, Springer Nature 15,141,286,290 pushed the response time down to the picosecond level 284 : a graphene transistor based terahertz photodetector was demonstrated with sensitivity 700 V W −1 at room temperature and 8-9 orders of magnitude faster due to hot-electron PTE effect ( Figure 7A). 141,285,286 Other examples include: propagated graphene plasmons were detected and imaged by thermoelectricity 287 ; flexibledetachable dual-output sensors of fluid temperature and dynamics with high-resolution (<0.19 K and < 0.03 cm s −1 ) was successfully synthesized 15 ( Figure 7B); a solarthermoelectric generator (SOTEG) or a dynamic piezothermoelectric generator can improve the power output by 24-158% when compared with traditional single energy conversion 288,289 ; device architecture design of SOTEG is possibly making full use of tandem solar cell 290 ( Figure 7C,D).…”

“…For example, low‐dimensional material‐based photothermoelectric (PTE) detectors have successfully pushed the response time down to the picosecond level 284 : a graphene transistor based terahertz photodetector was demonstrated with sensitivity 700 V W −1 at room temperature and 8‐9 orders of magnitude faster due to hot‐electron PTE effect (Figure 7A). 141, 285, 286 Other examples include: propagated graphene plasmons were detected and imaged by thermoelectricity 287 ; flexible‐detachable dual‐output sensors of fluid temperature and dynamics with high‐resolution (<0.19 K and < 0.03 cm s −1 ) was successfully synthesized 15 (Figure 7B); a solar‐thermoelectric generator (SOTEG) or a dynamic piezo‐thermoelectric generator can improve the power output by 24–158% when compared with traditional single energy conversion 288,289 ; device architecture design of SOTEG is possibly making full use of tandem solar cell 290 (Figure 7C,D).…”

“…Schematic of (A) graphene photothermoelectric detector device fabrication and principle of operation, Copyright 2018, Springer Nature (B) dual‐output sensors based on thermoelectric effects monitoring fluid temperature and dynamics, Copyright 2018, Elsevier Ltd. All rights reserved. (C) Photo‐Seebeck system under experiment (D) possible device architectures of SOTEGs, Copyright 2014, Springer Nature 15,141,286,290 …”

Polymer–Inorganic Thermoelectric Nanomaterials: Electrical Properties, Interfacial Chemistry Engineering, and Devices

“…For instance, thermoelectric devices enable the effective utilization of the previously wasted heat, thus providing promising solutions for optimizing power generation technologies and improving fuel energy efficiency (Sales, 2002 ; Bell, 2008 ). Moreover, advanced techniques such as solar cells are also benefited due to the heat management and light harvesting of thermoelectric devices (Jurado et al, 2019 ; Xu et al, 2019 ). The corresponding thermoelectric performance is defined as thermoelectric figure of merit ZT : ZT = S 2 T σ/κ, where S is thermoelectric power or Seebeck coefficient, T is absolute temperature, σ is electrical conductivity, and κ is thermal conductivity.…”

“…Due to these outstanding characteristics, polymer–inorganic nanomaterials can promote the value of ZT with enhanced compatibility, which leads to superior activity and stability in thermoelectric devices. In addition, via heat management and light harvesting, polymer–inorganic thermoelectric nanomaterials can also improve the efficiency of solar cells (Jurado et al, 2019 ).…”