Evaluation of Organic Electron Selective Contact for Hybrid PEDOT:PSS- Silicon Solar Cells

Hybrid PEDOT:PSS- silicon heterojunction solar cells have garnered significant interest over the past few years due to their low-temperature processes that are benign to thin-silicon substrates, and a wide variety of organic and inorganic material selections that are capable of solution processes. In this work, we investigate and compare the properties of three materials: buckminsterfullerene (C60), a common fullerene derivative, [6,6]-Phenyl C71 butyric acid methyl ester (PCBM) and an organic small-molecule 1,3-bis(2-(4-tert-butylphenyl)-1,3,4-oxadiazol-5-yl) benzene (OXD-7) to serve as the electron selective layer for the hybrid solar cells. The materials are separately dissolved in chlorobenzene (CB) and then bladed-coated onto the rear side of the hybrid solar cell. We have found that all devices show notable enhancement in the power conversion efficiency compared to the reference device without a rear interlayer between n-si wafer and the aluminum electrode. However, the devices with PCBM and OXD-7 show slight enhancement on the open-circuit voltage (~10mV net increase) and fill factor (~1% net increase), suggesting electron transport is facilitated. On the other hand, the device with C60 shows a clear improvement on the open-circuit voltage by almost 40mV, indicating a field passivation effect, while the fill factor is degraded by 2-3%. Further work on the carrier selectivity is still in progress and will be presented.