On the perfomance of a photosystem II reaction centre-based photocell

TL;DR

This study models a photosystem II-based photocell, revealing how vibrational modes influence current noise and offering insights into biological and photovoltaic applications of these complexes.

Contribution

It provides a theoretical analysis of charge separation in photosystem II complexes within photovoltaic devices, highlighting vibrational modes' role in noise reduction.

Findings

Vibrational modes do not increase power output.

Vibrational modes can suppress current noise.

Implications for biological regulation and molecular photovoltaics.

Abstract

The photosystem II reaction centre is the photosynthetic complex responsible for oxygen production on Earth. Its water splitting function is particularly favoured by the formation of a stable charge separated state via a pathway that starts at an accessory chlorophyll. Here we envision a photovoltaic device that places one of these complexes between electrodes and investigate how the mean current and its fluctuations depend on the microscopic interactions underlying charge separation in the pathway considered. Our results indicate that coupling to well resolved vibrational modes does not necessarily offer an advantage in terms of power output but can lead to photo-currents with suppressed noise levels characterizing a multi-step ordered transport process. Besides giving insight into the suitability of these complexes for molecular-scale photovoltaics, our work suggests a new possible biological function for the vibrational environment of photosynthetic reaction centres, namely, to reduce the intrinsic current noise for regulatory processes.