PERC Researchers Win Prestigious Engineering Prize

The 2023 Queen Elizabeth Prize for Engineering has been an occasion to celebrate four solar pioneers, who developed the widely used PERC technology that improved solar efficiency and supported a steep drop in costs over the past two decades.

The four awardees– Professor Martin Green of UNSW, Professor Andrew Blakers of ANU, and Dr Aihua Wang and Dr Jianhua Zhao were felicitated and formally presented with the award at a function yesterday for their invention and refinement of the Passivated Emitter and Rear Cell (PERC) solar cells.

The awards were presented by King Charles in a ceremony at Buckingham Palace on October 12.

The Queen Elizabeth Prize for Engineering (the QEPRize) is awarded annually to engineers of any nationality that have invented ground-breaking technologies of global benefit to humanity.

Speaking at the award show, Professor Martin Green said that “I hope that PERC technology winning the QEPrize will highlight the importance of accelerated solar adoption to address climate change.”

Over the last 40 years, Green and his team’s pioneering work, combined with that of many others, has transformed photovoltaic technology and dramatically reduced costs, with solar now the cheapest source of electricity in most countries.

The photovoltaic effect was first reported by Edmond Becquerel in 1839 and was able to be explained theoretically by Einstein’s 1905 work on the photoelectric effect. The first practical solar photovoltaic cells were developed at Bell Telephone Laboratories in 1954 and became the standard energy source for spacecraft. Commercial production for terrestrial use began in the 1970s, with the efficiency of commercial solar cells reaching 14% by the early 1980s.

The key contribution of this year’s Laureates lies in greatly boosting the energy conversion efficiency. It was believed that 20% efficiency was the practical limit for a single-layer silicon solar cell until papers by Green, Blakers, Wang and Zhao and others theoretically determined the maximum achievable efficiency lay close to 30%, with Green suggesting a higher practical limit of 25%.

In 1983, Green and Blakers at the University of New South Wales produced solar cells with 18% efficiency, surpassing the 16.5% recorded previously. Over the next few years, they published cell results of 19% and 20% efficiency.

In most solar cells, efficiency was limited, among other factors, by photon-generated electrons being lost through recombining with the thick doped silicon layer at the back surface. To overcome this, PERC introduced an additional layer on the back surface that helped prevent recombination and further, reflected unused photons back into the silicon to generate more electrons. The awardees and their colleagues published their first paper on PERC technology in 1989, boasting a record-setting 22.8% efficiency.

Green’s lab at the University of New South Wales held the global record for efficiency for 30 of the 40 years from 1983 to 2023, with Wang and Zhao leading the work which eventually reached Green’s 25% efficiency target.

The awardees opted to publish rather than patent, since commercial uptake seemed remote, freeing PERC technology to be widely adopted. It took two decades of development before PERC technology entered the mainstream. PERC technology is now the most commercially viable silicon solar cell technology for use in solar panels, recently accounting for almost 90% of the global solar cell market.

The awardees acknowledge that many people contributed to the PERC story, as reflected in the authorships of papers. The late Stuart Wenham is credited with pioneering work on hydrogenation to neutralise defects introduced during PERC cell manufacturing and field operation, and also was a pioneer in the laser processing used in commercial PERC cells.

Dick Swanson at Stanford University and Pierre Verlinden at Louvain and their teams contributed ground-breaking improvements to interdigitated back contact cells and contributed greatly to highly efficient laboratory and commercial solar cells.

Many people in research laboratories and companies around the world contributed to successful development of efficient and low-cost commercial PERC solar cells.