Scalable Green Manufacturing of Lead-Free Carbon Perovskite Solar Cells

Description

Aim: The aim of this project is to develop sustainable, low-cost roll-to-roll manufacturing methods to significantly improve production efficiency of carbon based Cs₂AgBiBr₆ (CABB) perovskite solar cells.

Background:

Lead-based Perovskite Solar Cells (PSCs) have achieved an enormous amount of progress in the last decade, with the latest record for Power Conversion Efficiency (PCE) at 27.0%, outperforming the current market leading silicon solar cells¹. This is largely due to several favourable properties such as high absorption coefficients, defects tolerance, and charge carrier mobility. In additional, perovskite thin films are solution processable, offering cost-effective and high throughput roll-to-roll compatible manufacturing options such as slot die coating and ink jet printing².

Lead based PSCs are starting to emerge on to the market in China and the US. However, a key technical challenge in the roadmap to their wide spread commercialisation is the use of toxic materials such as lead and hazardous solvents. An estimated 30 billion PV modules will be needed to achieve global net zero by 2050, of which PSCs are expected to make up a significant share. This is a 10-fold increase on current capacity – enough panels to build a staircase to the moon and back. The environmental cost could be tremendous if we do not address the issue of toxicity.

A recently emerging alternative to the lead-based perovskites is Cs₂AgBiBr₆ (CABB) double perovskites. Their negligible toxicity, highly moisture stability and favourable photovoltaic properties have made CABBs a research hotspot in the last few years³. To date they have demonstrated a PCE of up to 5%, relatively low compared to their lead-based counterparts. Although this is expected to rise rapidly given the current levels of research interest.

As well as the active perovskite layer of the solar cell, PSC devices require a complex architecture that includes electrical contacts, hole transport and electron transport layers. The hole transport layer (typically spiro-OMeTAD) and top electrical contacts (typically gold or silver) are very expensive and are often fabricated using non-scalable spin coating or vacuum deposition methods. Both of these factors are significant barriers to largescale high throughput manufacturing. An exciting and emerging alternative architecture is hole transport free device with a carbon-based top electrode. Carbon is cheap, can be sourced from recycled materials and can be deposited using scalable processes such as screen printing⁴. These devices are referred to as Carbon Perovskite Solar Cells (CPSCs).

It is our belief that CABB CPSCs are the future of sustainable solar energy power generation. As this new generation of materials reach maturity, now is the time to focus on low cost large scale green processing of CABB CPSCs.

Work Plan: This project will comprise of 2 strands: 1) roll-to-roll manufacturing optimisation of CABB perovskite layers, and 2) the fabrication and deposition of carbon contacts.

• The student will work with the existing team to optimise the CABB ink properties to ensure that it is compatible with several printing processes. In addition, they will develop a reliable and repeatable method for the fabrication of high quality CABB thin films using scalable processes such as slot die coating.
• The student will then build high quality CABB films into full scale solar cell devices with a carbon contact layer. This will require the development of a fabrication method to produce carbon paste and a deposition method such as screen printing to fabricate the contacts. The formulation and rheology of the carbon paste will be optimised to suit the requirements of the fabrication and deposition methods.

About the group: Dr Hughes and her team specialise in developing new materials and fabrication techniques to produce thin film solar cells. The team is in the process of carrying out an EPSRC funded feasibility study investigating non-toxic lead-free perovskite solar cells. The group currently consists of one post doc and three PhD students. The team also work closely with many colleagues at the University of Liverpool, including staff at Stephenson Institute of Renewable Energy and within the School of Engineering. Dr García-Tuñón and her team funded by an UKRI future leaders fellowship specialise in the design and characterisation of complex fluids for advanced materials processing with a focus on newly discovered materials made in the Materials Innovation Factory. Her fellowship has enabled the establishment of a new complex fluids and advanced materials lab, hosting capital equipment for formulation, rheology, printing and post-processing. 

We want all of our staff and Students to feel that Liverpool is an inclusive and welcoming environment that actively celebrates and encourages diversity. We are committed to working with students to make all reasonable project adaptations including supporting those with caring responsibilities, disabilities or other personal circumstances. For example, If you have a disability you may be entitled to a Disabled Students Allowance on top of your studentship to help cover the costs of any additional support that a person studying for a doctorate might need as a result.

We believe everyone deserves an excellent education and encourage students from all backgrounds and personal circumstances to apply.

Applicant Eligibility

Candidates will have, or be due to obtain, a Master’s Degree or equivalent from a reputable University in an appropriate field of Engineering. Exceptional candidates with a First Class Bachelor’s Degree in an appropriate field will also be considered.

Application Process

Candidates wishing to apply should complete the University of Liverpool application form applying for a PhD in **Aerospace / Civil / Materials / Mechanical** Engineering and uploading: Degree Certificates & Transcripts, an up-to-date CV, a covering letter/personal statement and two academic references.