High and low-dimensional mixed lead-tin perovskite thin films for photovoltaic applications
Lead Research Organisation:
University of Cambridge
Department Name: Physics
Abstract
In this project we are characterising a promising mixed-Pb:Sn low-bandgap 3D thin film perovskite structure such that it can be further developed and stabilised for photovoltaic applications in single-junction and tandem perovskite cells. Furthermore, we will build from the ground up a foundation on mixed-Pb:Sn 2D/3D thin film perovskites that also show photovoltaic applications owing to potentially higher ambient stability than their pure 3D counterparts. The work will be achieved through a combination of wet chemistry processing, chemical and material sample characterisation and measurements to determine the photophysics of these new hybrid structures.
Organisations
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509620/1 | 01/10/2016 | 30/09/2022 | |||
| 1948703 | Studentship | EP/N509620/1 | 01/10/2017 | 30/09/2020 | Edoardo Ruggeri |
| Description | Perovskites represent a promising route towards low-cost, efficient, abundant and customizable materials for photovoltaic applications. Two of the main hurdles towards their widespread commercialisation are however the poor ambient stability that plagues low-bandgap mixed-Pb:Sn composition, and the poor stability displayed in operating conditions across a wide range of compositions. This is often expressed as a progressive degradation of the physical active material, and of the device overall electrical performance. While 2D/3D film morphologies have been designed to enhance the ambient stability of mixed-Pb:Sn films, overcoming operational instability is still a major challenge. Understanding and visualising the origin of this degradation is a challenging task, as most operando studies provide very limited data due to the difficulties presented by studying a thin film of active material sandwiched into a full device stack. To get around this obstacle many operando device studies focus on lateral architectures. However, the case can be made that these are not representative of real-word operating devices, which instead most often use top-down layouts. We therefore developed a grazing-incidence wide-angle X-ray scattering technique to probe the operando structural evolution of mixed-cation mixed-halide perovskite thin films integrated in top-down full photovoltaic device stacks under applied illumination and bias, probing the material directly through the top metal electrode, and not measuring an exposed surface. This allowed us to observe and uncover mechanism that were previously inaccessible. Using the capabilities of our pitch-adjustable custom-made device tester, we succeeded in visualising crystallographic structural evolution under operational conditions in dry helium and humid air at both the top contact layer/perovskite interface as well as in the perovskite bulk, highlighting the differences in structural evolution between the two. In our studies we investigated two different devices, a normally-operating and a defective one (higher series resistance), and we observed the stark differences in ionic migration behaviour between them. The normally-operating device appeared to incur a remixing of the halide ions, associated with a compression of the lattice in the out-of-plane direction, and correlating with current stability. Conversely, a humid atmosphere or a higher series resistance induced halide segregation, with associated current degradation. We supported these findings with operando photoluminescence studies on the same architectures, where full current degradation correlated with a strong red-shifting of the emission, a typical tell-tale sign of halide segregation in these mixed-halide perovskite materials. These studies were carried out on mixed-cation mixed-halide compositions due to their higher stability in ambient conditions with respect to the more delicate Pb:Sn compositions. This allowed us to optimise the measurement conditions and requirements, and assess the overall feasibility of the investigation with the outlook of applying this now well-developed technique to mixed-Pb:Sn 3D and 2D/3D devices in future measurements. It is expected that the development of this powerful novel technique for operando structural probing of full device stacks will generate considerable interest among researchers, as it provides a valuable route for investigating structural degradation in devices of marketable architectures operating in real-word conditions, visualising effects and crystallographic evolutions previously unable to be uncovered. |
| Exploitation Route | Significant work is still required before this class of materials can have a market breakthrough. While we could visualise the effects of applied bias and illumination on the crystallographic structure of a perovskite full photovoltaic device stack, the elimination of the ionic migration processes that appear to be at the culprit of device degradation still requires significant effort. This is a purely research-oriented task, and as such we expect the necessary work to be carried out in an academic or private research setting for the foreseeable future. The know-how, expertise, and world-class laboratories and facilities available at the University of Cambridge make me confident that this institution is one of the best-suited ones in the country and in the world to lead research on this matter all the way up to the maturement of this techonology for its commercialization. |
| Sectors | Energy,Other |
| Description | HYbrid PERovskites for Next GeneratION Solar Cells and Lighting |
| Amount | € 1,759,732 (EUR) |
| Funding ID | 756962 |
| Organisation | European Research Council (ERC) |
| Sector | Public |
| Country | Belgium |
| Start | 11/2017 |
| End | 10/2022 |
| Description | The Origin of Non-Radiative Losses in Metal Halide Perovskites |
| Amount | £273,163 (GBP) |
| Funding ID | EP/R023980/1 |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Sector | Public |
| Country | United Kingdom |
| Start | 05/2018 |
| End | 04/2021 |