Critical role of Interface and perovskite lattice in high-efficiency and photostable solar cells
Résumé
Hybrid perovskites have recently seen an unprecedented improvement in the power conversion efficiency in photovoltaics devices, and therefore are very promising materials for developing efficient and low-cost single junction solar cells [1-3]. However, a critical issue is the limited understanding of the correlation between the degree of crystallinity and the emergent perovskite/hole (or electron) transport layer on device performance as well as photo-stability. Los Alamos National laboratory (LANL) developed an efficient growth procedure for 3D halide perovskites in inverted perovskite cell architecture using PEDOT-PSS as a p-type hole transporting material (HTM) [4]. The initial collaboration between FOTON/ISCR and LANL led to the observation of a reversible self-healing mechanism under light soaking [5] and showed that the aging of the precursor solution plays a role in the nucleation of the perovskite crystallites [6]. In this study, we show that growth of methylammonium lead perovskites (MAPbI3) on nickel oxide (NiO) HTM, results in the formation of ordered and crystalline thin-films with enhanced crystallinity, leading to characteristic XRD Bragg peak width reminiscent of exclusively observed in the tetragonal phase in single-crystals. Photo-physical and interface sensitive measurements reveal a reduced trap density at the MAPbI3 perovskite/NiO interface in comparison with perovskites grown on PEDOT: PSS. Photovoltaic cells exhibit a high open circuit voltage (1.12 V), indicating a nearideal energy band-alignment. Moreover, we observe photo-stability of photovoltaic devices up to 10- Suns, which is a direct result of the enhanced crystallinity of perovskite thin-films on NiO. These results elucidate the critical role of the quality of the perovskite/HTL interface in rendering highperformance and photo-stable optoelectronic devices [7].
[1] Lee, M. M., Teuscher, J., Miyasaka, T., Murakami, T. N. & Snaith, H. J. “Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites”. Science 338, 643 (2012).
[2] Burschka, J. et al. “Sequential deposition as a route to high-performance perovskitesensitized solar cells”. Nature 499, 316-319 (2013).
[3] Jeon, N. J. et al. “Solvent engineering for high-performance inorganic–organic hybrid perovskite solar cells”. Nat. Mater. 13, 897-903 (2014).
[4] Nie, W. et al, “High-efficiency solution-processed perovskite solar cells with millimeterscale grains”. Science 347, 522 (2015).
[5] Nie, W. et al, “Light-activated photocurrent degradation and self-healing in perovskite solar cells”, Nat. Comm. 7, 11574 (2016).
[6] Tsai, H. et al,” Effect of Precursor Solution Aging on the Crystallinity and Photovoltaic Performance of Perovskite Solar Cells” Adv. Ener. Mat. 7, 1602159 (2017)
[7] Nie, W. et al, Adv. Mater. (In press)