Abstract
The organic passivated carbon nanotube (CNT)/silicon (Si) solar cell is a new type of low‐cost, high‐efficiency solar cell, with challenges concerning the stability of the organic layer used for passivation. In this work, the stability of the organic layer is studied with respect to the internal and external (humidity) water content and additionally long‐term stability for low moisture environments. It is found that the organic passivated CNT/Si complex interface is not stable, despite both the organic passivation layer and CNTs being stable on their own and is due to the CNTs providing an additional path for water molecules to the interface. With the use of a simple encapsulation, a record power conversion efficiency of 22% is achieved and a stable photovoltaic performance is demonstrated. This work provides a new direction for the development of high‐performance/low‐cost photovoltaics in the future and will stimulate the use of nanotubes materials for solar cells applications.
Highlights
With the use of a simple encapsulation, a record power conversion efficiency of 22% is achieved and a stable the passivated emitter and rear cell (PERC) have reached power conversion efficiencies (PCEs) of ≈ 23%,[3] and new generation scaled silicon heterojunction cells have pushed past 24% on industrial producphotovoltaic performance is demonstrated
Nafion films were spin cast from an alcohol/water mix (2.94 wt% Nafion/92.06 wt% aliphatic alcohols/5 wt% H2O) and the relative humidity (RH) was increased from 17–33% over a period of 800 min
The initial increase in lifetime is related to the electrochemical passivation effect of Nafion. This effect is enhanced by O2 in the atmosphere but the ingress of small quantities of water into the film has a negative effect and τeff was reduced to ≈ 26% for a RH of 33%
Summary
The addition of the CNTs leads to a decrease in the stability with reduction of ≈69% of the initial lifetime value already occurring within this short time period This suggests that CNTs accelerate the ingress of water, most likely by increasing the porosity of the film but possibly due to endohedral water transport to the interface.[35] This physiochemical mechanism is sketched, Supporting Information. For the final use with CNTs in a solar cell, a 10% water Nafion film was the best compromise between the required thickness and passivation, see Figure S4 and Table S2, Supporting Information. Further work is required to increase the Voc, of c-PC based solar cells, but with a proven environmental stability, the combination of nanomaterials with organic passivation layers appears to provide a promising new avenue for low-cost and high-PCE PV devices in the future
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