# Artificial Photosynthesis: Is Computation Ready for the Challenge Ahead?
## 1 Introduction  
The need to find new sources of energy production for our everyday consumption is one of the most pressing issues of our age. To overcome the dependence on fossil fuels and to assess renewable energy resources, innovative paths must be followed, to go beyond the conventional technologies that are already available. Moreover, considering the climate change problem and environmental pollution as a result of production and consumption of energy from fossil fuels, the need for green and renewable energy sources is a milestone which needs to be reached in the next two decades. If no necessary actions are taken, inevitably our future generations will be adversely affected. To counteract these problems, the European Union (EU) set a \"Renewable Energy Directive\" with a target of 55% reduction of greenhouse gas emission and reaching carbon neutrality by 2050 [1]. In the frame of these ambitious goals, the need of novel efficient materials is a priority for developing a competitive technology, with much effort already dedicated to bio-ethanol and other biofuels, novel photovoltaic technologies, including organic and perovskite solar cells, advanced batteries and supercapacitors, as well as electro- and photocatalytic systems for hydrogen production and a new class of fuel cells for transport. A different approach to this problem is to take advantage and mimic what nature was able to perfect upon millions of years of evolution. Yet, one of the biggest challenges in modern science is to replicate in an artificial way the most basic processes performed by nature, such as photosynthesis. This fundamental process has been found to be a challenge to reproduce in laboratory settings using artificial, man-made systems/devices [2; 3; 4]. This is due to the many components needed from light-driven charge separation to the transportof charges between different photosynthetic reaction centers and to the final production of reducing equivalents, subsequently used for solar fuels synthesis. Although almost all of these steps are nowadays fully understood, mimicking this complex photosynthetic machinery in the full solar-to-fuel artificial devices that use water as the sole source of reducing equivalents is still prohibitive at an industrial scale. In particular, in the last five years research effort has been focused on the creation of an \"artificial leaf\" device that is able to produce clean energy from absorption of light, with some encouraging results [5,6]. Devices with external quantum efficiency of 30% has been reported [7], yet the overall efficiency is still below 1% [8,9] due to the cell design and lack of control over the light harvesting (LH) systems orientation. Despite being still in its infancy, this relatively-new research approach has the potential of taking advantage of two well-known branches of research: photobiology and nanomaterial science. In fact, by combining in a synergetic way the optical and electronic properties of different nanomaterials, it might be possible to create a new class of biomimetic, hybrid devices with enhanced impact on sustainability. The potential of such collaboration is to take advantage of the best features of the two fields and design and build devices that mimic the photosynthetic apparatus of plants in a laboratory setting. In nature, photosynthesis occurs through a highly complex apparatus in which the light is absorbed and converted into electrons via two large membrane proteins, such as photosystem I (PSI) and photosystem II (PSII) [10,11] found in higher plants as well as their counterpart (i.e., LH2, which contain a vast range of carotenoids and bacteriochlorophylls depending on the species) found in purple bacteria [12] with a multi-step proton-coupled electron transfer chain reaction that has been perfected during evolution to efficiently convert solar energy into the biological hydrogen-storage compound, reduced nicotinamide adenine dinucleotide phosphate.