Photosynthetic Protein Complexes as Bio-photovoltaic Building Blocks Retaining a High Internal Quantum Efficiency

Abstract

Photosynthetic compounds have been a paradigm for biosolar cells and biosensors and for application in photovoltaic and photocatalytic devices. However, the interconnection of proteins and protein complexes with electrodes, in terms of electronic contact, structure, alignment and orientation, remains a challenge. Here we report on a deposition method that relies on the self-organizing properties of these biological protein complexes to produce a densely packed monolayer by using Langmuir-Blodgett technology. The monolayer is deposited onto a gold electrode with defined orientation and produces the highest light-induced photocurrents per protein complex to date, 45 μA/cm(2) (with illumination power of 23 mW/cm(2) at 880 nm), under ambient conditions. Our work shows for the first time that a significant portion of the intrinsic quantum efficiency of primary photosynthesis can be retained outside the biological cell, leading to an internal quantum efficiency (absorbed photon to electron injected into the electrode) of the metal electrode-protein complex system of 32%.

Biomimetic Photodiode Device With Large Photocurrent Response Using Photosynthetic Pigment-Protein Complexes

“…16 These results show superior performance compared to the previously reported work on similar systems where the waveform showed a nonsaturating profile with long rise and decay times in the order of minutes. [9][10][11] To evaluate the endurance of the photocurrent response, cycling stability test was performed by monitoring the photocurrent response as the device continuously cycled between dark and illuminated states. For cycling test, the light intensity was fixed at 320 mW/cm 2 .…”

“…1 Most recently, the biomimetic strategy has been borrowed from photosynthetic organisms utilizing the whole photosynthetic pigments and proteins to be incorporated into the man-made photocurrent devices. [7][8][9][10][11][12][13] Thereby, the high efficiency of the photosynthesis might be retained in the artificial devices. Bilayer structure of recombinant ferredoxin and chlorophyll shows one directional transport of electron from chlorophyll to ferredoxin molecule during visible light exposure.…”

“…10 The highest photocurrent density response of 45 µA/cm 2 is obtained when the protein complex was densely packed via Langmuir film deposition. 11 Most of these works were conducted in bio-photo-electrochemical cells which required electrolyte solution and must be confined and sealed. Up to now, only one work reported the solidstate bio-photovoltaic device albeit the inferior device performance.…”

On the mechanism of ubiquinone mediated photocurrent generation by a reaction center based photocathode

“…Particular attention has been paid to the Photosystem I complex from oxygenic phototrophs [15][16][17] and both the RC and RC/light harvesting complexes from anoxygenic purple photosynthetic bacteria such as Rhodobacter (Rba.) sphaeroides [4][5][6][7][8]10,[18][19][20][21][22][23]. Major preoccupations of this work have been the development of strategies for effective interfacing of the positive and negative terminals of the photovoltaic protein to the working and counter electrode, either through direct binding or the use of diffusional mediators [4][5][6][7][8][16][17][18][19][20][21][22][23][24][25][26][27].…”

“…sphaeroides [4][5][6][7][8]10,[18][19][20][21][22][23]. Major preoccupations of this work have been the development of strategies for effective interfacing of the positive and negative terminals of the photovoltaic protein to the working and counter electrode, either through direct binding or the use of diffusional mediators [4][5][6][7][8][16][17][18][19][20][21][22][23][24][25][26][27]. In the case of RC's from purple bacteria a particularly effective strategy has been to use analogues of the natural electron donor and electron acceptor, cytochrome (cyt) c2 and ubiquinone-10 (UQ10), to connect the photovoltaic protein to the two electrodes [18,20,22,[27][28][29].…”