Research in energy and the environment is now more important than ever as issues related to global warming, air quality, and clean water impact more and more of the world’s population. Energy and environmental experts from the University of Nottingham Ningbo China (UNNC) and Ningbo Institute of Materials Technology and Engineering (NIMTE) are striving to improve power conversion efficiency (PCE) beyond 25% for back-contact perovskite solar cells to provide clean energy.

Recently, an article entitled ‘Device physics of back-contact perovskite solar cells’, has been published in the academic journal Energy & Environmental Science with authors by Zhenhai Yang, Weichuang Yang, Xi Yang, J. C. Greer, Jiang Sheng, Baojie Yan, and Jichun Ye. The full paper is the result of research collaboration between Faculty of Science and Engineering, UNNC and NIMTE. 

Energy & Environmental Science is a prestigious international journal published by the Royal Society of Chemistry in the United Kingdom and boasts an ‘impact factor’ of 30.289. According to Journal Citation Reports, Energy & Environmental Science is the No. 1 journal in the world for Environmental Science and 2nd in the world for Energy & Fuels, which places it as the 37th top ranked journal in the world for all subject areas including medicine, chemistry, physics, engineering, biology, mathematics, etc.

“This work is an indication of the success that a dedicated PhD student such as Zhenhai Yang can achieve. I am very proud of Zhenhai and his work, his research has led to a significant scientific contribution in area that can lead to real benefit, improving solar cells leads to cheaper and cleaner energy benefitting everyone.” said Professor Jim Greer.

Zhenhai Yang is a PhD candidate in the Joint Doctoral Training Programme between UNNC and NIMTE, CAS. He is co-supervised by Professor of New Energy Technology Jichun Ye in the NIMTE and by Li Dak Sum Chair Professor in Advanced Electronic Materials and Devices Jim Greer at UNNC.

The paper looks at ways of improving photovoltaic solar cells. Over the past decade, perovskite solar cells (PSCs) have shown a remarkable improvement in power conversion efficiency (PCE) and it has been the fastest-advancing solar technology in the world. However, their full potential has not been achieved due to a lack of a complete understanding of their operation from a device physics perspective. In their study, a detailed photoelectrical model for back-contact PSCs is developed by coupling a drift-diffusion description of a free charge transport model with ion migration currents and emitted-carrier generation resulting from photon recycling.

Zhenhai Yang, the lead author of this paper said, “In the past few years, perovskite solar cells (PSCs) have been becoming a promising alternative as a competitive technology in the photovoltaic (PV) community. The photoelectrical losses of traditional sandwich PSCs have been minimized, leaving little room for further improvements in efficiency. Therefore, an essential change in device structure is necessary to overcome the bottleneck. The concept of back-contacts (BCs) that was previously explored for Si-based optoelectronic devices, has been introduced to PSCs. PSCs featuring BC design can eliminate parasitic absorption by the front-side contact inherent to traditional sandwich structures, and provides an opportunity for screening a suitable antireflective coating and passivation materials, endowing PSCs with a facile strategy for structural design. In terms of BC-PSCs, additional advantages of eliminating pinholes and protecting the perovskite film from damage by subsequent layers are offered. Moreover, perovskite properties, such as photon recycling and simultaneous in-situ and in-operando film characterization can be studied in BC devices. However, BC-PSCs are still limited by shallow understanding and a fundamental theory system is in urgent need. Here, we constructed a detailed photoelectrical model to investigate the inherent behaviour of BC-PSCs. The simulation results clarified the design principles and carrier transport dynamics of the BC-PSCs based on the processes of carrier generation, transport and recombination. Here, we predicted that a high PCE exceeding 25% can be expected if the interface passivation and film quality were well controlled. Various electron/hole transport layers with different conduction band and valence band offsets were reviewed, providing a plethora of screening opportunities for functional materials with high efficiency. Furthermore, the effect of mobile ions and photon recycling phenomenon on device response of BC-PSCs was comprehensively investigated by coupling the traditional photoelectrical model with ion migration and photon recycling models. Herein, our results unveil a possibility for further promoting the performance of PSCs and provide valuable guidelines for the design and fabrication of BC-PSCs.”

Faculty of Science and Engineering, UNNC is dedicated to delivering world-changing research and fosters a research environment that is conducive to research. Currently, Faculty of Science and Engineering has 14 Chair Professor appointed across a range of key research areas including new materials, intelligent manufacturing, green chemistry, and computer science.

Professor Jim Greer is one of the Chair Professor who is also a world-leading expert in his field. His research focuses on semiconductors, microchips, and electronics on the nanoscale. Before joining the UNNC, he has working experience in research centres in Europe, the United States, and Asia. He has also secured more than RMB 50 million research funding from international and national foundations, and industry.

Please join us to congratulate Zhenhai Yang and Professors Jim Greer and Jichun Ye on their research achievements.

Please join us to congratulate Zhenhai Yang and Professors Jim Greer and Jichun Ye on their research achievements.