To tackle the global energy crisis and achieve carbon neutrality, we must change the way we produce and use energy. Solar energy and battery technologies are at the heart of this transformation. Solar energy is projected to become Europe's on of the main sources of electricity by 2050. Improving the performance of solar technologies is essential to meet this demand sustainably and cost-effectively. However, even the most advanced commercial solar cells are rapidly approaching their theoretical efficiency limits. To go further, we need technologies that can harvest sunlight more effectively by overcoming the physical limitations of today’s photovoltaic devices.
One promising solution is to make better use of sunlight by using the energy of the photons that are typically lost via transmission and heat in single junction solar cells. Spectral conversion (SC) is one of the approaches to achieve this solution. Through SC, light that would otherwise be wasted is transformed into energy the solar cell can use, via a spectral conversion layer typically placed at the bottom or at the top of the cell. This project, SpinSC, focused on understanding and optimising the underlying electronic processes that make spectral conversion possible, aiming to increase solar cell efficiency in a way that complements existing technologies.
Two advanced light conversion mechanisms—singlet fission and triplet–triplet annihilation—are central to this approach. These processes are governed by the behaviour of electrons and their spin, a fundamental quantum property. Unfortunately, the spin interactions involved in these conversions are complex and short-lived, making them difficult to control and study with traditional methods. SpinSC tackled this challenge by combining state-of-the-art simulation techniques with experimental insight to explore and control the spin dynamics driving spectral conversion.
The project was hosted at the University of Padua and in collaboration with the University of New South Wales in Sydney, leveraging their interdisciplinary expertise that bridges quantum physics, materials science, and photovoltaics. SpinSc aimed to answer fundamental questions: How do molecular structure and movement influence spin-based energy conversion? What role do interactions with atomic nuclei play in these processes? And how can we use light itself to induced molecular reorganisation and spin states conversion in ways that boost efficiency?
The ultimate objective if this project was not just to explain how spin-mediated spectral conversion works, but to create practical design rules that can be used to build more efficient solar devices. If successful, these findings could lead to new materials for organic solar cells, potentially exceeding 45% efficiency when combined with existing technologies.
