Global research into solar photovoltaics has seen a steady increase over the past 20 years as the technology has developed and those behind it strive to advance its cause for both existing and new applications in the evolving global energy mix.

The leading lights in PV research, which takes in several distinct fields, are the US and Germany. Not only do they both produce a significant amount of research but they are also key players in its exchange. Indeed, owing to the US and Germany being such dominant players, North America and Europe top the research table by continent.

Many other countries involved in developing PV technology rely on research from the US, while Denmark, Australia and Switzerland are also known to be actively engaged in information sharing, which they supplement with their own proprietary work.

Over the 10 years spanning 1999—2009 there was a distinct upturn in the publication of relevant research papers on solar PV. Between 2000 and 2004 the specific areas of research focus widened. For instance, between 2005 and 2009 research into organic/polymer technologies more than doubled from the level of the previous 10 years and an empirical study suggests that trend is set to continue in the coming years.

By area of study, the most popular PV research sectors were organic/polymer, thin-film silicon and dye sensitised solar cell (DSSC), with the US, Germany, Australia, Denmark and Switzerland contributing the most.

PV to Challenge Grid Within 10 Years?

A survey of PV experts from the US and Europe found they expect PV generation to compete commercially with grid electricity sometime between 2015 and 2020.

The development of storage systems for renewable energy appears to remain a key factor for the development of PV technology, according to the experts — about half of whom underscored its importance.

To date the solar PV industry has been largely dominated by the presence of the silicon-based PV technology, but as research continues some experts are already starting to look to a time when it could be overtaken as the dominant force in the industry.

Key technology research fields for PV 1990—2009

Potential challengers to silicon-based PV technology include thin-film technologies such as amorphous-silicon, CIS or CdTe.

This is likely to be followed by the single crystal or cast polycrystal technology and new medium thick crystalline film, said the experts.

But it is organic/polymer PV technology which is likely to be the real successor to silicon, despite it being considered by some as incipient. Nevertheless, there is confidence from some quarters that the technology is ready for a market application which will be 90% focused on the portables and consumer products sector. Other applications are likely to be off-grid for telecoms and transportation and on-grid for residential and commercial and others.

Organic/polymer’s PV market share is rated at 25%—30% currently and is based on its light weight, low cost, fabrication speed and adaptability. But it is faced with a major challenge as it strives to become a large-area, low-cost PV solution with long-term stability — namely the need to achieve a stronger efficiency and the reproducibility of performance across the device area.

Research into PV technologies is expected to continue in the short, mid and long term and while work on high efficiency solar cells like third generation technologies is expected in all three periods, research into organic/polymer technology is predicted to take an upturn in the mid- to long term.

Call research at the Lawrence Berkeley National Laboratory (Credit: LBNL)

Research on thin-film technologies like silicon, CIS and CIGS as well as bulk crystalline silicon is only expected to be take place in the short term, said those surveyed.

In the short term, thin-film silicon will experience a faster growth rate than other areas, according to the experts. In the medium term organic/polymer will be followed by thin-film (CIS/CIGS) and in the long term by quantum dot/nano technologies.

The two main challenges for PV experts are finding suitable applications for organic/polymer solar cells in their current formuntil their application can be further explored and developed as the technology matures; and the unification of efficiency, stability and large-scale processing.

The high costs that currently present the key barrier to PV are set to be mitigated by the acceleration of the energy market, increased production capacity and future economies of scale — although unifying efficiency, stability and large-scale processing will present another challenge.

But the outlook is positive, with a steady increase in the technology’s power conversion efficiency, as well as a recent influx of funds and grants for the field from the US, Europe and China.

By 2020 an established, cost-competitive PV industry should reflect the different efficiencies and costs of the various PV technology sectors of the day. Experts also believe the significant recent growth of PV technology shows that its inclusion in the energy mix is not only viable, but may help meet current and future supply challenges.

With current levels of research, the PV market may grow at a rate of 25%—30% per year for the next 20 years.

Sven Seidenstricker and Christian Linder are both lecturers at the Institute for Human Factors and Technology Management at the University of Stuttgart in Germany.

DSCC Takes Research Lead in PV

DSSC research became more prominent between 2000 and 2004 and has since remained relatively steady. The most prolific subject in the periods 2000—2004 and 2005—2009 was organic/polymer, on which the paper classed as the most important was also published.

Quantum dot/nano is a relatively new research field. No paper was published on it until 1999, although research has increased since 2000.

Overall, PV research and the relevant number of articles published on all of its sectors have increased since 1990 — with 7, 37 and 35 papers published in 1990—1999, 2000—2004 and 2005—2009, respectively.

There is a slight decrease in the final period as not all of the published articles have been collated.

Small But Promising — BIPV

Grid-connected building-integrated PV (BIPV) solutions are fast becoming the most promising of all the current small-scale applications of solar technology, according to experts in the field. The use of thin-film technology in buildings is viewed as preferable to the traditional c-Si solar cells. Drawing support from government incentives, the technology has witnessed widespread commercialisation and a growth in market share over the past 10 years.