Perpustakaan Digital ITB

Lead sulfide (PbS) colloidal quantum dot solar cells (CQDSCs)present the distinctive ability to utilize short-wave infrared light, good ambientstability, and convenient solution-based fabrication processes and thus attractmuch attention in the photovoltaic researchfield. The performance of CQDSCshas been improved by constructing the ZnO/PbS heterojunction, due to suitableband levels and electron mobility of ZnO electron transfer layer (ETL).However, the huge number of defects in low-temperature processed ZnO causean unbalanced carrier-related processes, which restrict further performanceenhancement andflexible production of CQDSCs. Here, we described a facilemethod to passivate defects in low-temperature sol?gel ZnO by introducingpolyethylenimine (PEI) into the precursor solution. Versus the original ZnOfilm, the composite ZnO:PEIfilms exhibit better crystallization because of theZn?N interaction. A series of electronic analyses have shown that the additionof PEI reduces the work function (WF) of ZnO and increases the built-involtage (Vbi) at the heterojunction interface, suggesting that the carrier separation is improved in the depletion region of solarcells. The carrier transport in ZnO ETL is also optimized by PEI, since the electron mobility of ZnO is maximized when themass faction of PEI is 5%. In addition, the carrier recombination is effectively suppressed in the ZnO:PEI based solar cellsproved by the increased carrier lifetime. Consequently, a power conversion efficiency (PCE) of 7.30% was achieved with theZnO:PEI 5%film versus 5.84% for the reference cell?this was attributed to the optimized carrier-related processes.