High-performance Flexible Perovskite Solar Cells By ALD-assisted Interface Modification

Flexible perovskite solar cells(PeSCs)hold great potential as a leading technology for large-scale roll-to-roll production of highly efficient renewable energy sources.To achieve long-term bendability and competitive photovoltaic properties for flexible PeSCs,it is important to develop high-performance low-temperature processed electron transport materials(ETM)and bendable electrodes.The thermal decomposition problem of perovskite materials fabricated on the surface of low-temperature processed ZnO limits the application prospect of ZnO as ETM in PeSCs.Although the thin film of silver nanowires(AgNWs)show good optical and mechanical properties,there is still a long way before they can be efficiently used in flexible PeSCs due to its rough surface and low thermal stability.In this thesis,firstly the mechanisms for thermal decomposition of perovskite materials on ZnO surface were studied using X-ray photoelectron spectroscopy(XPS).Then,an atomic-layer-deposited TiO2 modification layer was introduced between perovskite materials and ZnO to eliminate the decomposition of the perovskite materials.A champion PCE of 18.26%was achieved by optimizing the thickness of TiO2.At last,a fully indium-free flexible composite electrode,consisting of solution-processed AgNWs conductive network,a sol-gel-derived ZnO protective layer for smoothing the surface,and an atomic-layer-deposited TiO2 modification layer,was applied to flexible perovskite solar cells which realized a power conversion efficiency(PCE)of 17.11%.Moreover,flexible PeSCs using this composite electrode are repeatedly bendable,retaining 77%of their initial efficiency after 2000 bending cycles at a radius of 6 mm.Because of the ease of use and remarkable improvement in efficiency,this flexible composite electrode will help to enable the low-cost roll-to-roll processing of flexible PeSCs.