Towards a 50% efficient solar cell

Lead Research Organisation: Imperial College London
Department Name: Physics


Multi junction solar cells have the ability to exceed 50% power conversion efficiency but in order to do so, new semiconductor materials are required. Since the thickness of these materials are of the order of the wavelength of light and often highly radiative efficient, the photonic structure of the solar cell requires careful attention. In this project we address the need for near-IR subcells and consider a range of semiconductor materials with band-gaps between 1.2-0.7eV, based around III-V and group V alloys. In a 4-junction solar cell structure, these sub-cells can contribute towards raising the solar cell efficiency to reach 50% under solar concentration.
The project will involve solar cell device design, and evaluation of practical devices using standard electrical measurements (light-IV, dark-IV, quantum efficiency) as well as semiconductor spectroscopy, both steady state and transient. Capacitance and impedance spectroscopy will also be used to determine the role of trap states in candidate materials. Epitaxial growth and processing of samples, will take place at collaborating institutes.

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509486/1 01/10/2016 31/03/2022
1858551 Studentship EP/N509486/1 01/10/2016 06/08/2020 Phoebe Pearce
Description The research supported by this award have focused on two main topics: (1) new materials for multi-junction solar cells and (2) the optics of solar cells.
1. With material supplied by IQE plc, we have managed to do extensive spectroscopic measurements of SiGeSn (silicon-germanium-tin) alloys, i.e. investigations of the interaction of the material with light which can give us information about the properties of the material relevant to its use in solar cells. We have confirmed that the correct bandgap can be achieved with SiGeSn to absorb the correct wavelengths of light in a multi-junction solar cells. These are key steps for designing an efficient solar cell using SiGeSn.
2. Work on the optics of solar cells has yielded a variety of outcomes. This includes contributions to Solcore, an open-source Python package for modelling solar cells. In addition, work investigating the reliability of modelling when there is uncertainty in the input data (specifically, the optical constants of the materials used in the simulated structure) was published recently.
Exploitation Route The data published so far, and to be published within the next year of the PhD, will help myself and collaborators, as well as other research groups, to design more efficient solar cells, especially multi-junction devices containing optical structures. These types of cells are especially useful for concentrator photovoltaics, for use in space applications (e.g. satellites), and possibly for niche applications where a limited area is available and high efficiency is worth paying for, e.g. for transport applications or portable electronics.
Sectors Aerospace, Defence and Marine,Electronics,Energy,Transport

Title Solcore 
Description Solcore is an Python 3 package for designing and modelling many aspects of solar cells, which has been developed in the Quantum Photovoltaics group at Imperial College for many years, but has existed in its current, freely available form since 2018. Solcore allows calculations of idealised solar cells at the theoretical limit, or can be used to design realistic devices taking into account e.g. realistic absorption profiles, quantum confinement effects, shading effects, etc. Optical and electrical calculations can be performed using multiple different solvers depending on the degree of accuracy required, or the suitability of each method. This award contibuted especially to the development of the optical solvers within Solcore. 
Type Of Technology Software 
Year Produced 2018 
Open Source License? Yes  
Impact Since becoming publicly available, Solcore has been gaining users and developers, and has been used to generate data used in several publications.