Researchers from TU Delft and TU Eindhoven have recently demonstrated world record performance for hybrid thin-film solar cells. Amorphous silicon and semiconducting polymers are two promising solar absorbers for low-cost large-scale thin-film solar cells.
However, solar cells based on a single absorber deliver relatively low solar-to-electricity conversion efficiencies due to the insufficient solar spectrum utilization. A solar-to-electricity conversion efficiency of 13.2% has been obtained by stacking the two absorbers in a hybrid multijunction device with effective optical and electrical management.
The work of former PhD Hairen Tan (TU Delft and recent NWO Rubicon Laureate) and PhD Alice Furlan (TU/e) has been published in the journal Advanced Materials on 18 January 2016.
Hybrid multijunction solar cells
Multijunction solar cells, in which two or more solar cells with absorbers having different optical properties are stacked on top of each other, offer an effective strategy to enhance the efficiency of photovoltaic energy conversion. Such devices absorb a larger part of the solar spectrum and convert the energy of the solar spectrum into electricity more effectively. The hybrid approach uses a wide-bandgap amorphous silicon to absorb visible sunlight and a low-bandgap polymer layer to absorb infrared light. High conversion efficiencies of 11.6% and 13.2% are achieved in tandem and triple-junction configurations, respectively.
Merits of hybrid approach
The hybrid tandem approach leads to a higher conversion efficiency as compared to their single component devices. It combines the advantages of both amorphous silicon and polymer solar cells, such as abundant and non-toxic raw materials, light weight and flexibility, low cost and low processing temperature, and allows fabrication of ultra-thin solar cells. The solution processing of polymer solar cells is also fully compatible with the vacuum deposition of amorphous solar cells, making the hybrid approach feasible for the low-cost and mature roll-to-roll mass production. The high conversion efficiencies in the tandem hybrid solar cells were achieved by employing effective light management to ensure that all absorber layers contribute equally to the photocurrent.
The collaborative research work has been carried out within the Photovoltaic Material and Devices group of Prof. Miro Zeman and Prof. Arno Smets (TU Delft) and the Molecular Materials and Nanosystems group of Prof. René Janssen (TU/e & DIFFER). Both groups are part of Solliance, which is a partnership of R&D organizations from the Netherlands, Belgium and Germany working in thin-film photovoltaic technologies. For more information please visit: www.solliance.eu.