Effect of concomitant anti-solvent engineering on perovskite grain growth and its high efficiency solar cells
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Published online 25 August 2020 | https://doi.org/10.1007/s40843-020-1415-2
Effect of concomitant anti-solvent engineering on perovskite grain growth and its high efficiency solar cells 1,2
Tong Liu , Xiaofei Dong
1,2*
1,2
ABSTRACT The grain boundaries and interface properties in the active layers of perovskite solar cells (PSCs) are important factors affecting the performances of the devices. In this work, a simple and fast concomitant annealing process is established by inducing the secondary growth of the grains using the antisolvent o-dichlorobenzene (o-PhCl2) or chlorobenzene (PhCl) to suppress the volatilization of solvent molecules during the + FA0.80MA0.15Cs0.05Pb(I0.85Br0.15)3 (FA, CH5N2 , formamidine; + MA, CH3NH3 , methylamine) film annealing procedure. The effects of anti-solvent molecules on the phase transformation, grain boundary fusion and morphology evolution of perovskite films are systematically investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that anti-solvent molecules can inhibit solvent evaporation in the active layers and promote crystallite dissolution and ordered secondary growth along the surfaces of large grains. That can promote the formation of large grains and the passivation of surface defects, and can be favorable for the separation and transportation of photocarriers in the active layer. Consequently, the power conversion efficiency (PCE) of PSCs can be effectively improved, with a PCE of 20.72% being achieved by a secondary growth perovskite film optimized with o-PhCl2. Moreover, the efficiency remains at 85% of its initial value after 2400 h of treatment in a natural indoor environment with a relative humidity of 45±5%. Keywords: anti-solvent vapor annealing, perovskite grains, secondary growth, defect passivation, solar cells
INTRODUCTION Solar cells with CH3NH3PbI3-type active layers have been increasingly considered as a crucial research direction in the renewable energy field over the past decade [1,2], and the highest certified power conversion efficiency (PCE) of 1 2
*
1,2
, Juncong Li , Hongli Liu , Shirong Wang
1,2
and Xianggao Li
1,2*
perovskite solar cell (PSC) is 25.2% [3,4]. The quality of perovskite active layer is the key factor affecting the performance of the PSCs. Controlling the grain growth process has been proven to be feasible to obtain perovskite films with high crystallinity, large grains [5], few grain boundaries, low trap densities and carrier recombination rate [6,7]. Advanced engineering approaches for improving the film quality can be classified into two categories: (a) controlling the growth rate by changing the synthesis, such as additive engineering [8] and solvent engineering [9,10]; (b) regulating the film morphology by post-treatment, including interface modification [11,12] and solvent vapor-assisted (SVA) methods [13,14]. The latter focuses on the induction of the secondary grain growth to improve the film quality and device performance. Unlike interface modification, the SVA meth
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