The Efficiency Reaches a Plateau in Inverted Schottky Quantum Dot Solar Cells

Schottky lead sulfide (PbS) quantum dot (QD) solar cells (SCs) have the advantage of simple device fabrication while pn heterojunction SCs benefit from efficient carrier extraction induced by a front depletion region. Herein, we used low-work function transparent conducting oxide (L-TCO) to create a front contact with p-type PbS QD layer. The configuration, denoted as inverted Schottky, combines the mentioned advantages of Schottky and pn structures. A series of inverted Schottky cells having a structure of L-TCO/p-PbS QDs/MoOx/Au-Ag and normal Schottky cells with a structure of ITO/p-PbS QD/Li-Al were fabricated for comparison. Current - voltage measurements showed that as the thickness of p-PbS QD layer increased the power conversion efficiency (PCE) of normal cells maximized at 160 nm while PCE of inverted cells reached a plateau. The observed plateau in inverted Schottky cells can reduce the technical difficulty in maintaining the thickness of PbS QD layer.