Plasmonic effect in pn-junction solar cells based on layers of semiconductor nanocrystals: Where to introduce metal nanoparticles?

• Plasmonic effect in pn-junction solar cells.
• p-type layer of CZTS nanocrystals.
• n-type layer of Cu@AgInS2 nanocrystals.
• Silver nanoparticles act as electron-traps hindering electron-transport.
• Metal nanoparticles should be placed only in p-type layer so that transport of electrons in plasmonic solar cells remains unaffected.

We have introduced metal nanoparticles in pn-junction solar cells to study plasmonic effect in such devices. Here, the junction was based on a layer of copper–zinc–tin–sulfide (CZTS) nanocrystals as a p-type semiconductor and another layer of copper-diffused silver indium disulfide (Cu@AgInS2) nanocrystals as an n-type material in sequence. We introduced silver nanoparticles at different locations of pn- and also of np-junctions: (i) in the p-layer, (ii) in the n-layer, (iii) in both the layers, and (iv) at the interface between the layers of p- and n-type nanocrystals. The results in both pn- and np-junctions show that the devices with metal nanoparticles in p-type layer evidenced a substantial increase in energy conversion efficiency of solar cells as compared to other devices and the control device without any silver nanoparticles. We have inferred that the presence of silver nanoparticles in the depletion layer might have narrowed down the width of the region; metal nanoparticles in the n-layer acted as electron-traps to localize them hindering electron-transport and thereby reducing the efficiency of such plasmonic solar cells. Our results have shown that while introducing metal nanoparticles in solar cells, they should be placed only in the p-layer so that transport of electrons in plasmonic solar cells remains unaffected.

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