Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - PEOPLE (PEROVSKITE OPTOELECTRONICS)

Teaser

During the implementation of this project, we focused on the critical problems that limited the practical applications of perovskite optoelectronics. Right now there are several well-known issues of perovskite materials and their applications:1. The notorious stability issues...

Summary

During the implementation of this project, we focused on the critical problems that limited the practical applications of perovskite optoelectronics. Right now there are several well-known issues of perovskite materials and their applications:
1. The notorious stability issues of perovskite materials
2. The longtime operation of optoelectronic devices based on perovskites materials (thermal, moisture, and long-time stability of the devices)
3. The toxic element of Lead
4. the anomalous hysteresis in the current-voltage curves, etc.
In the project, named PEOPLE, we have obtained several important breakthroughs in the perovskite optoelectronics. For example, we recently published a high-profile paper in a prestigious journal Nature Communications (Nature Communications 2018, 9, 608). This paper reports an infrared LED with record high efficiency of 12.7%, and revealed the physics origins of efficiency roll off. Most importantly, an effective way was provided to reduce the efficiency roll off.

The importance for society:
Perovskites provide promising new opportunities for optoelectronic devices that can mitigate greenhouse gasses emissions and help to reach the Paris Agreement goals. For example, solar cells directly harvest renewable energy from the sunshine, and LEDs help to use energy more efficiently. It is highly desirable and even crucial to develop low-cost but highly efficient optoelectronic devices based on solution-processed semiconductors (i.e. perovskites), which are ideally suited for scaling up the production using ink-based printing or spray-coating techniques. The development of low-cost perovskite optoelectronic devices will also contribute to the readiness and competitiveness of Europe in the new era of energy-efficient technologies with enormous potential.

The overall objective of this project is to develop a lasting collaboration between top-class research teams in Europe and Asia that fosters progress in the broad area of perovskite optoelectronics through progress in materials science, chemistry, device physics, photophysics, and device engineering.
With these central tenets in mind the project will attempt to accomplish the following objectives:
• Enable a schedule of exchange visits between the European and Chinese partners encompassing both junior and senior level staff.
• ensure that there is a true transfer of knowledge between the European and Chinese partners. This knowledge transfer is envisioned as a means of complementing existing knowledge.
• Facilitate future partnerships between the partners, especially between those partners which traditionally did not have these links. This could result in future proposal submission to national and European granting agencies. Future research partnerships could also potentially lead to reciprocal hiring from partner groups, an important advantage of exchanges being the chance for junior members to later extend their networks to search for job opportunities.
• Enable a dissemination of the research activities through common workshops, meetings and joint publications (open access).
• Protect intellectual property (IP). The PEOPLE work plan contains work packages of significant technological relevance. Therefore, prior to any publication, potentially patentable materials will be identified and the necessary measures will be taken.

Work performed

Detailed information of the publications

1: Research work on perovskite light emitting diodes:
Minimising efficiency roll-off in high-brightness perovskite light-emitting diodes, published in Nature Communications 2018, 9, 608.

Efficiency roll-off is a major issue for most types of light-emitting diodes (LEDs), and its origins remain controversial. Here we present investigations of the efficiency roll-off in perovskite LEDs based on two-dimensional layered perovskites. We concluded that the efficiency roll-off in perovskite LEDs is mainly due to luminescence quenching which is likely caused by non-radiative Auger recombination. This detrimental effect can be suppressed by increasing the width of quantum wells, which can be easily realized in the layered perovskites by tuning the ratio of large and small organic cations in the precursor solution. This approach leads to the realization of a perovskite LED with a record external quantum efficiency of 12.7%, and the efficiency remains to be high, at approximately 10%, under a high current density of 500 mA cm−2.

2. A research article on perovskite solar cells:
Approximately 800-nm-Thick Pinhole-Free Perovskite Films via Facile Solvent Retarding Process for Efficient Planar Solar Cells, published in ACS Applied Materials & Interfaces 8 (50), 34446-34454
Device performance of organometal halide perovskite solar cells significantly depends on the quality and thickness of perovskite absorber films. However, conventional deposition methods often generate pinholes within ∼300 nm-thick perovskite films, which are detrimental to the large area device manufacture. Here we demonstrated a simple solvent retarding process to deposit uniform pinhole free perovskite films with thicknesses up to ∼800 nm. Solvent evaporation during the retarding process facilitated the components separation in the mixed halide perovskite precursors, and hence the final films exhibited pinhole free morphology and large grain sizes. In addition, the increased precursor concentration after solvent-retarding process led to thick perovskite films. Based on the uniform and thick perovskite films prepared by this convenient process, a champion device efficiency up to 16.8% was achieved. We believe that this simple deposition procedure for high-quality perovskite films around micrometer thickness has a great potential in the application of large area perovskite solar cells and other optoelectronic devices.

All the above mentioned published research results have been disseminated on the project website (http://ec-people.eu) and scientific website (e.g. ResearchGate) and through national and international conferences.

Final results

A serial of exciting research results has emerged from the support of the PEOPLE project. For example, we have revealed the physics origins of efficiency roll off in perovksite LEDs and provided an effective way to reduce it. We have also developed the first lead-free double perovskite solar cell. These research results are beyond the state of the art and will make great impacts in the research field of perovskite optoelectronics.
Firstly, the research outcomes will boost and promote the research and development of perovskite optoelectronic devices. The applications prospect will attract the attention from industry area since research and applications on optoelectronics become more and more important in the marketplace.
Secondly, the research will also deepen public awareness of optoelectronics device and applications.
Last but not the least, the most important results from this project is the human resources generated. Through implementation of this project, researchers with different backgrounds and expertise are allowed to complementarily exchange knowledge and skills. It is expected that the recognition and training of young talent in the development of novel perovskite optoelectronics will have long lasting benefits for the development of individuals.

Website & more info

More info: http://ec-people.eu/.