New molecule drives solar-cell cost down and efficiency up
Michael Grätzel with a Grätzel cell ©EPFL
EPFL scientists in collaboration with Kaunas University of Technology have developed a new molecule that increases the efficiency of perovskite solar cells to 16.9% – the highest yet – using a new hole transporter.
Solar panels sensitized with the lead-containing perovskites are among the best options for market-suitable solar panels. However, the selective extraction of positive and negative charges limits the light-to-electricity conversion efficiency of perovskites, which is why they must be combined with prohibitively expensive hole transport materials. Publishing in Angewandte Chemie, EPFL and Kaunas University scientists have overcome the problem of cost by synthesizing a small molecule that is both cheap to integrate with perovskites, and raises the efficiency of solar panels to 16.9%, their highest value yet using new hole transporting materials.
A perovskite solar cell includes a perovskite as the light-harvester. Because of their high energy-conversion, perovskites have attracted intense attention for thin-film solar panels. These are essentially a sandwich of different layers comprising the pervoskite and selective contacts materials for extraction of electrons and positive charges (“holes”). One of these layers is called a “hole-transporter”. The hole-transporter is crucial for energy-conversion efficiency and requires high-purity materials. However, this entails complicated synthetic procedures, which drive up the costs of these solar panels.
The labs of Mohammed Khaja Nazeeruddin and Michael Grätzel at EPFL, have now developed a small molecule that can act as a highly efficient hole-transporter. The molecule, called V886, is synthesized in two simple chemical steps from commercially available and relatively inexpensive materials. This makes it considerably cheaper to integrate with perovskite solar panels compared to the spiro-OMeTAD, which showed the highest energy-conversion efficiency in the field. The new molecule’s efficiency is 16.9%, which is the second highest after Spiro-OMeTAD. But considering its low cost, it represents a superior candidate for perovskite solar panels.
This work involved a collaboration of EPFL’s Laboratory of Photonics and Interfaces with the Kaunas University of Technology (Lithuania), and Abengoa Research.
Reference
Gratia P, Magomedov A, Malinauskas T, Daskeviciene M, Abate A, Ahmad S, Grätzel M, Getautis V, Nazeeruddin MK. Methoxydiphenylamine-Substituted Carbazole Twin Derivative: An Efficient Hole-Transporting Material for Perovskite Solar Cells.Angew Chem Int Ed 16 July 2015. DOI: 10.1002/anie.201504666