Hybrid Perovskite Heterojunctions

Lead Research Organisation: University of Glasgow
Department Name: School of Chemistry

Abstract

Perovskite solar cells are the fastest growing solar technology in history, with demonstrated power conversion efficiencies exceeding 23%, above established solar technologies such as polycrystalline silicon, CIGS or CdTe. The main advantage of perovskites is their ease of processing, i.e. they can be printed from simple inks, and their elements are in abundance; ensuring their long-term low cost. This results in very high-quality materials that can also be applied in lighting applications such as general room lighting, displays for hand-held devices and larger screens and communication devices. It is highly unusual that low-cost materials that can efficiently convert light to electricity can also efficiently do the reverse process of electricity to light. Manufacturing these kinds of materials does not require the expensive high-tech infrastructure currently needed to make electronic components. This makes this family of materials extremely attractive for many important technological sectors beyond solar energy.

The main aim of our project is to improve the performance and stability of perovskite solar cells by introducing a novel layered perovskite material to extract charge from the device. This approach removes the requirement to employ very expensive organic layers currently in use and will lead to significant further cost-savings, making the technology more attractive for commercial enterprises.

To achieve this, our project aims to introduce moisture barrier layers that can efficiently allow electrical current flow only in one direction through them based on perovskite ``quantum-well'' structures, i.e. very thin sheets of the perovskite material (several atom layers in thickness) that are sandwiched between equally thin plastic sheets. By carefully selecting the appropriate plastic sheet material, the structure becomes more resistive to water, and thus more stable, while maintaining the high-quality electronic properties of the perovskite family.

By developing these novel structures, our project will enable the manufacture of new types of electronic devices beyond solar cells. For instance, materials that show quantum-well properties are very useful for the fabrication of lasers. These are integral to information technologies and are also used in many other applications that could be even more widespread if they were sufficiently cheap.

Planned Impact

Knowledge:

The knowledge generated by this project will contribute to the international research effort to develop low-cost solar cells. The broad scope of the research will also help facilitate the transfer of ideas between researchers and add to the UK's research profile. Demonstrating new applications for the fascinating perovskite family of materials should generate considerable interest within both the academic and public spheres. As such, a key aspect towards maximising the impact of the work is engagement in an academic setting in the form of international conferences, for which funds have been requested. Our team will present the research results at conferences specifically targeted at perovskite materials, such as ABXPV and PSCO, as well as more general international materials conferences such as MRS and HOPV. The team will additionally pursue traditional knowledge dissemination outlets, i.e. high-impact journals in the field such as Nature or the Advanced Materials families, as well as make use of social media such as Twitter and Facebook to disseminate the results.


Economy:

Solar is the fastest-growing source of new energy worldwide, projected to reach £400 Bn by 2022 and generate hundreds of thousands of jobs. Perovskites are an excellent candidate for tandem solar cells with silicon, improving the performance of existing systems and thus will accelerate the spread of PV globally.

HYPER-junctions addresses stability concerns and aims to boost the efficiency of thin-film perovskite solar cells. This family of materials currently achieves the gold standard for a PV technology: high power conversion efficiencies with low material costs and compatible with solution-processing. Further improvements will benefit the UK by enabling access to a cheap, efficient PV technology and will maintain the UK's leading edge on perovskite research.

The interdisciplinary nature of the research, which borders on materials science, physics, and chemistry will have a high impact on the broad scientific community and an ever increasing number of start-up companies researching into the applications of hybrid perovskites, from lighting, photonics, hybrid electronics, electrochemical systems and recently memristors. This project will help create a platform for solution-deposited systems that exhibit quantum confinement. It will enable new types of co-creative research and commercial innovation produced by engineers in the fields of materials and optoelectronics. New job opportunities will follow from that.

Technology:

We expect that the new technology to be developed in this project will lead to a patentable technology. Preparation of patent applications will be carried out via the relevant expertise in this area available at NU Enterprise services. In addition, several team members are early career researchers and will take advantage of the variety of programmes for early career entrepreneurs offered at Newcastle University in the form of the ACTION Programme, EPSRC's Impact Acceleration Account, and the EU-funded ARROW program, to maximize our commercial impact.


People:

This project will involve training two postdoctoral researchers and one University-Industry co-funded PhD student who will develop wide-ranging experimental and theoretical skills in what is a rapidly growing and high profile area. In particular, they will receive training relevant to the semiconductor industry in terms of growth of thin film semiconductors and characterisation as well as skills relevant to designing autonomous electronics design. The training is expected to lead to well-rounded scientists perfectly positioned not only within the multi-disciplinary research world but also able to satisfy the increasing demand for highly trained individuals by companies in the field.
 
Description The project is still at an early stage and therefore the focus has been on studying the fundamental properties of baseline materials and their initial application in perovskite solar cells. We have performed advanced optical characterisation and started exploring how charge carriers are generated and their mobility within the structure with advanced Terahertz spectroscopy. Our findings suggest that quantum confinement leads to a high exciton binding energy, which limits charge transport in the system. Our preliminary measurements indicate that we must decrease the interlayer distance of the materials in order to improve on this parameter. We have begun optimising their application in perovskite solar cells and our results show power conversion efficiencies (PCE) in excess of 19.5%, very close to our 20% PCE deliverable.

We have begun studying the interfacial charge transfer/charge recombination between the layered perovskite and the archetypal perovskite layers. Our preliminary results show that the layered perovskite significantly reduces surface recombination and can be used to control the strain of the underlying film. We are finalising the study and will be aiming to get a publication out as soon as possible.
Exploitation Route We have now investigated a range of layered materials in depth. We have identified the signatures for exciton dissociation and hot carrier cooling employing THz spectroscopy and will report on their timescales in an upcoming publication. These results can be used to fine-tune the structure of the large cation used in this system to maximise charge generation and hence improve the performance of perovskite solar cells employing layered materials. In addition, our insights between surface recombination and control of strain can be used to further engineer the interface and improve the overall performance of perovskite solar cells.
Sectors Chemicals,Energy

 
Description Collaboration with Warwick University 
Organisation University of Warwick
Department Department of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution We have prepared a variety of layered perovskite material samples.
Collaborator Contribution The Milot group at the University of Warwick have fully characterised our samples of layered materials employing THz spectroscopy, transient absorption, cryo-UV Vis, and time-resolved PL
Impact One review paper has been published and we have a publication in preparation.
Start Year 2020