1900100 (1 of 10) © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.advsustainsys.com FULL PAPER Solar Heat-Enhanced Energy Conversion in Devices Based on Photosynthetic Membranes and PEDOT:PSS-Nanocellulose Electrodes Gábor Méhes, Mikhail Vagin, Mohammad Yusuf Mulla, Hjalmar Granberg, Canyan Che, Valerio Beni, Xavier Crispin, Magnus Berggren, Eleni Stavrinidou,* and Daniel T. Simon* DOI: 10.1002/adsu.201900100 convert solar energy into electricity by leveraging the complex process of photo- synthesis, useful both as energy generators and sensors for various physical inputs. [1–9] With accelerating climate change and growing demand for energy, such bio-based methods have been identified as a prom- ising route toward “green” energy. [10] Thylakoid membranes (TMs), the com- partments inside chloroplasts, algae, and cyanobacteria in which the light-dependent reactions of the photosynthetic energy conversion are initiated, constitute an interesting model system for biohybrid light-harvesting. Indeed, broad-spectrum light absorption, efficient water splitting, a near-unity light-to-charge conversion efficiency, optimized excitation energy and electron transport, photodamage protection, and self-organization and self- repair, all being properties of TMs, are strongly desired attributes of future intel- ligent solar energy harvesting technology. However, integration of TMs and isolated photoprotein complexes with technology poses several challenges, including complex preparation, poor stability, and limited photocurrents. [11–13] To address these challenges, prom- ising and novel biohybrid devices and electrodes have been demonstrated by wiring/coupling TMs to electrodes via oligo- electrolytes, [14] carbon nanotubes, [15] conducting polymers, [16] Energy harvesting from photosynthetic membranes, proteins, or bacteria through bio-photovoltaic or bio-electrochemical approaches has been proposed as a new route to clean energy. A major shortcoming of these and solar cell technologies is the underutilization of solar irradiation wavelengths in the IR region, especially those in the far IR region. Here, a biohybrid energy- harvesting device is demonstrated that exploits IR radiation, via convection and thermoelectric effects, to improve the resulting energy conversion performance. A composite of nanocellulose and the conducting polymer system poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is used as the anode in biohybrid cells that includes thylakoid membranes (TMs) and redox mediators (RMs) in solution. By irradiating the conducting polymer electrode by an IR light-emitting diode, a sixfold enhancement in the harvested bio-photovoltaic power is achieved, without compromising stability of operation. Investigation of the output currents reveals that IR irradiation generates convective heat transfer in the electrolyte bulk, which enhances the redox reactions of RMs at the anode by suppressing diffusion limitations. In addition, a fast-transient thermoelectric component, originating from the PEDOT:PSS- nanocellulose-electrolyte interphase, further increases the bio-photocurrent. These results pave the way for the development of energy-harvesting biohybrids that make use of heat, via IR absorption, to enhance energy conversion efficiency. Dr. G. Méhes, Dr. M. Vagin, Dr. M. Y. Mulla, Dr. C. Che, Prof. X. Crispin, Prof. M. Berggren, Prof. E. Stavrinidou, Prof. D. T. Simon Laboratory of Organic Electronics Department of Science and Technology Linköping University 60174 Norrköping, Sweden E-mail: eleni.stavrinidou@liu.se; daniel.simon@liu.se Dr. H. Granberg Papermaking and Packaging RISE Bioeconomy Research Institutes of Sweden 11486 Stockholm, Sweden The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adsu.201900100. 1. Introduction Biohybrid light-harvesting systems, such as bio-photovoltaic cells (BPVCs) and bio-photoelectrochemical cells (BPECs), Dr. V. Beni Department of Printed Electronics RISE Acreo Research Institutes of Sweden 60221 Norrköping, Sweden Prof. X. Crispin, Prof. M. Berggren Wallenberg Wood Science Center Department of Science and Technology Linköping University 60174 Norrköping, Sweden Adv. Sustainable Syst. 2020, 4, 1900100