WP Leader: David Lane
WP Participants: Cranfield, Bath, Durham, Northumbria
There is now 30-40 years of good data showing the development of world record PV efficiencies for a spread of different technologies with time. While the technologies are diverse (e.g. Si, organics, CIS/CIGS, CdTe etc) they all show a similar rate of technological improvement, as shown in the figure: They all increase at a rate of 0.45 ± 0.05% per annum regardless of technology type. Each then reaches a technological plateau, particular to the materials system being used.
Fig. Development of PV device efficiency year on year. All technologies improve at about the same rate, then hit a technological plateau.
The aim of this WP is to use modern rapid screening methods to increase the rate of progress. We are doing this in two ways:
1. Rapid screening of new materials:
The aim is to screen very large numbers of new materials combinations using experiments to search for materials properties with good PV performance. Traditionally this is done by making a sample with each composition, and testing it individually. In this approach, a single wafer of material is deposited with a gradation of compositions. We then use automatic mapping of both the composition and properties across the wafer to generate a matrix of information. In this way, many hundreds of experiments are replaced by just a few. The data is held in ’Äòlibraries’Äô contained in a bespoke data base.
In PV-21 we have used this approach to screen new chalcogenide materials. Generally we have made metal alloy layers and sulphurised or selnised them. They have been probed by advanced x-ray diffraction mapping, for optical absorption, and for photo-electrical activity.
2. Rapid screening of device performance.
A similar approach may be used in device optimisation. Rather than make a series of devices with one parameter changed, the full range of that parameter space may be evaluated in a single run, if that parameter is something that can be controlled over a wafer. We have done some preliminary experiments using thickness variation in CdTe/CdS solar cells and also examining the CdS/TCO interface. The Cranfield team will roll this approach out more generally, with a full database approach.
