Photoconducting Atomic Force Microscopy (pc-AFM) image of a smooth polymer-nanowire based organic solar cell. Image: National Physics Laboratory
National Physical Laboratory (NPL) scientists have achieved a
significant breakthrough in the metrology of organic photovoltaics. The
research demonstrated a new type of atomic force microscopy that can ‘see’ down
into a working organic photovoltaic cell and relate its 3D nanoscale structure
to its performance.
Photovoltaic solar cells have become a much more common
sight over recent years, often installed on rooftops where they quietly convert
sunlight into clean electricity for homes and businesses.
An organic photovoltaic cell is a type of solar cell that
uses organic (carbon-based) electronics and could potentially be a cheaper,
more efficient, and flexible alternative to today’s photovoltaic systems. The
technology is on the verge of commercialization but several obstacles remain,
including a necessary increase in performance.
Many recent advances have occurred due to recognition of the
pivotal role that morphology plays in efficiency, but it was previously
difficult to measure exactly how form and structure affect electrical
characteristics and therefore performance.
This research demonstrated that it is possible to obtain
structural and electrical information, both on the surface and below the
surface to a depth of at least 20 nm in operating organic solar cells. The new
measurement method is based on a technique called photoconducting atomic force
microscopy (pc-AFM) that uses a nanoscale probe to measure topography and
photocurrent generation at the same time.
This technique can provide direct correlation between the
nanometer-scale morphology of a working organic solar cell and its performance
This breakthrough will improve understanding of the
technology, allowing manufacturers to improve the efficiency of their products
by optimizing the nanometer-scale structure of the organic photovoltaic
The work has benefited from strong links with Imperial
College London, who contributed with their material and device fabrication
A manuscript describing the research has been
published in Energy and Environmental Science.