Improved thermal/chemical stability of flexible Ag NWs/Chitosan composite electrode integrated by chemical welding and sequential protection for better PV performance.

An integration strategy of chemical welding and subsequent protection was demonstrated to address silver nanowires (Ag NWs)-based issues. Preferentially, a halogenated salt of NaCl solution was used to stimulate the junction welding thus to reduce the junction resistance, by virtue of the autocatalytic redox of Ag atoms with halogen ions and dissolved oxygen molecules. Subsequently, chitosan, possessing the biocompatible, degradable, environmentally friendly non-toxic features, was embedded to protect Ag NWs. With these two steps, the composite electrode consisting Ag NWs and chitosan reaches a lowest sheet resistance of ∼8 Ω, with a transmittance over 80% at 550 nm, along with high thermal and chemical stabilities, accompanying with excellent flexibility. Besides, it also prompts a synergistic improvement when pioneered in Cu(In, Ga)Se2(CIGS) device as a transparent conductive electrode. It yields a power conversion efficiency of 6.6%, with 32% improvement relative to that bare Ag NWs, and 85% of the conventional one. Our findings present a new strategy for addressing instable/inefficient Ag NWs-based devices, driving their rapid development and its practical applications.

In Situ Electrochemical Treatment Evoked Superior Grain Growth for Green Electrodeposition-Processed Flexible CZTSe Solar Cells.

Flexible Cu2ZnSnSe4 (CZTSe) solar cells gradually attract much attention due to their low-cost, lightweight, and environmentally friendly features. However, the efficiency of flexible CZTSe solar cells obtained through the nonvacuum green electrodeposition process remains sluggish (3.82%), far away from that obtained from other methods (∼10% by magnetron sputtering). Herein, a championed 6.33% efficiency of flexible CZTSe solar cells prepared by the electrodeposition process is achieved through an in situ electrochemical treatment (ET) process. It is found that the ET process drives the formation of a thin MoOx layer, evoking a series of beneficial results, thus accounting for an enhancement in photovoltaic performance. With the ET process, the MoSe2 thickness is compressed and Cu- and Sn-related undesirable defects/secondary phases are inhibited, leading to improved film quality. Additionally, it prolongs the depletion region width and minority lifetime, accelerates the charge separation and collection, relieves the band tails, and favorably reverses the band bending from downward to upward at/near grain boundaries. With these effects, the efficiency increases from 4.21% to 6.33%, far beyond the highest reports on electrodeposited flexible CZTSe solar cells. Our findings offer a promising way to improving Mo foil-based flexible devices and mark a significant breakthrough for the development of electrodeposition-processed flexible CZTSSe-based solar cells.