EES Blog

The significance of new solar cell technologies tends to rest heavily on their measured efficiency. But compounding small mistakes in measuring that efficiency can lead to values up to five times higher than the true reading, says Henry Snaith from the University of Oxford, UK. 

Snaith has therefore set out a guide that illustrates the factors that should be taken into consideration when measuring efficiency, and outlines the potential sources of error. It is an attempt to restore confidence in literature claims and make them more easily comparable – both within fields and across different types of cells including dye-sensitised solar cells (DSSCs), organic photovoltaics and hybrid solar cells. The guidance includes how to mask cells to get an accurate measure of the test area; the type of lamps to use and how to calibrate them; and the importance of positioning the cell in exactly the same place as the calibration reference. 

‘There’s an ongoing stream of papers in which it’s not entirely clear exactly how the measurements have been made,’ says Snaith. And worse than that, some papers claim values that appear to be grossly overinflated. That has an impact on genuine claims, Snaith explains. ‘If, for example, someone claims their hybrid solar cell has an efficiency of 4% when it’s really more like 1%, that makes it problematic for someone else to write an exciting paper when they’ve genuinely improved something to 1.5%.’ 

Read the paper from Energy & Environmental Science:

How should you measure your excitonic solar cells?
Henry Snaith
Energy Environ. Sci., 2012, Accepted Manuscript
DOI: 10.1039/C2EE03429H

UK scientists have employed liquid crystals consisting of alternating hydrophobic and hydrophilic layers as a framework for liquid photogalvanic cells.

The system is over five times more solar-to-electrical-power-conversion-efficient-per-pound sterling than dye-sensitised photovoltaic solar cells, whilst being an electrochemical capacitor of high voltage and power efficiency, say the researchers.

Mobile computing devices such as smart phones and tablets require efficient, readily-rechargeable and lightweight power sources that are capable of being moulded into whichever spatial geometry and volume are required for this technology. The integration of solar-rechargeable batteries (such as liquid photogalvanic cells) into such devices increases their portability through reducing dependence on accessible shore power.

Reas the ‘HOT’ paper today:
Photogalvanic Cells Based on Lyotropic Nanosystems: Towards the use of Liquid Nanotechnology for Personalised Energy Sources
J E Halls and J D Wadhawan,
Energy Environ. Sci., 2012, DOI: 10.1039/c2ee03169h

In this ‘HOT’ paper from EES, Michael Grätzel and colleagues investigate the use of platinum-free electrocatalysts in dye-sensitized solar cells (DSSC). This new research has lead to a new record efficiency for an organic redox couple DSSC of 7.9%.

Read Grätzel’s latest paper:

Influence of the counter electrode on the photovoltaic performance of dye-sensitized solar cells using a disulfide/thiolate redox electrolyte
Julian Burschka, Vincent Brault, Shahzada Ahmad, Livain Breau, Mohammad K. Nazeeruddin, Benoît Marsan, Shaik M. Zakeeruddin and Michael Grätzel
Energy Environ. Sci., 2012,
DOI: 10.1039/C2EE03005E