Octylammonium Iodide Induced In-situ Healing at perovskite/Carbon Interface to Achieve 85% RH-moisture Stable, Hole-Conductor-Free Perovskite Solar Cells with Power Conversion Efficiency >19%

Perovskite/carbon interface is a bottle-neck for hole-conductor-free, carbon-electrode basing perovskite solar cells due to the energy mismatch and concentrated defects. In this article, in-situ healing strategy is proposed by doping octylammonium iodide into carbon paste that used to prepare carbon-electrode on perovskite layer. This strategy is found to strengthen interfacial contact and reduce interfacial defects on one hand, and slightly elevate the work function of the carbon-electrode on other hand. Due to this effect, charge extraction is accelerated, while recombination is obviously reduced. Accordingly, power conversion efficiency of the hole-conductor-free, planar perovskite solar cells is upgraded by approximate to 50%, or from 11.65 (+/- 1.59) % to 17.97 (+/- 0.32) % (AM1.5G, 100 mW cm(-2)). The optimized device shows efficiency of 19.42% and open-circuit voltage of 1.11 V. Meanwhile, moisture-stability is tested by keeping the unsealed devices in closed chamber with relative humidity of 85%. The in-situ healing strategy helps to obtain T-80 time of >450 h for the carbon-electrode basing devices, which is four times of the reference ones. Thus, a kind of internal encapsulation effect has also been reached. The in situ healing strategy facilitates the fabrication of efficient and stable hole-conductor-free devices basing on carbon-electrode.

Automated summary

In this article, an in-situ healing strategy is proposed to strengthen the perovskite/carbon interface by doping octylammonium iodide into the carbon paste. This strategy accelerates charge extraction and reduces recombination, leading to an upgraded power conversion efficiency of perovskite solar cells.