Improving the photovoltaic performance for PbS QD thin film solar cells through interface engineering

Interfaces exist between functional layers inside thin film optoelectronic devices, and it is very important to minimize the energy loss when electrons move across the interfaces to improve the photovoltaic performance. For PbS quantum dots (QDs) solar cells with the classical n-i-p device architecture, it is particularly challenging to tune the electron transfer process due to limited material choices for each functional layer. Here, we introduce materials to tune the electron transfer across the three interfaces inside the PbS-QD solar cell: (1) the interface between the ZnO electron transport layer and the n-type iodide capped PbS QD layer (PbS-I QD layer), (2) the interface between the n-type PbS-I layer and the p-type 1,2-ethanedithiol (EDT) treated PbS QD layer (PbS-EDT QD layer), (3) the interface between the PbS-EDT layer and the Au electrode. After passivating the ZnO layer through APTES treating; tuning the band alignment through varying the QD size of PbS -EDT QD layer and a carbazole layer to tune the hole transport process, a power conversion efficiency of 9.23% (V_oc of 0.62 V) under simulated AM1.5 sunlight is demonstrated for PbS QD solar cells. Our results highlights the profound influence of interface engineering on the electron transfer inside the PbS QD solar cells, exemplified by its impact on the photovoltaic performance of PbS QD devices.