SBIR-STTR Award

To achieve the predicted high power conversion efficiencies of multijunction amorphous silicon solar cells (a:Si), efficient use of all incoming solar radiation is necessary. Multijunction solar cell devices are efficient collectors of incident light, in theory, because light with energy less than the bandgap edge of the first junction may be effectively absorbed by the junction below. In practice, significant reflectance losses occur because of optically mismatched layers. An innovative solution to this problem is the use of optically optimized, thin film multilayer front and back contact designs. The objective of the project is to investigate a novel design approach for optically optimized front and back contact configurations for a tandem a:Si solar cell device. The optimized thin film stacks serve to reduce reflection losses as well as to maximize the transmission of incident light to the device below.Anticipated Results/Potential Commercial Applications as described by the awardee:Commercial applications will be low cost, high efficiency multijunction a:Si alloy solar cells for terrestrial and space power applications.

In order to achieve the predicted high power conversion efficiencies of multijunction amorphous silicon solar cells (a:Si), efficient utilization of all incoming solar radiation is necessary. In practice, significant reflectance losses occur due to optically mismatched layers. An innovative solution to this problem is the use of optically optimized front and back contact configurations for a tandem a:Si solar cell device. The Phase I work demonstrated the technical feasibility of incorporating optical enhancement layers within the tandem solar cell device structure. The objective of the Phase II program is to develop and fabricate two and four terminal optically enhanced multijunction a:Si solar cells. The high efficiencies of these tandem devices will be achieved through the use of the novel optical enhancement layer designs that were shown to be feasible in Phase I. Following the successful development of high efficiency tandem devices, cost elements associated with the use of optical enhancement layers will be evaluated.Anticipated Results/Potential Commercial Applications as described by the awardee: Commercial applications consist of low cost, high efficiency multijunction two or four terminal a:Si solar cells for the terrestrial energy marketplace, with possible space power applications.Topic 21: Photoltaic Research