Dopant-additive synergism enhances perovskite solar modules

Abstract

Perovskite solar cells (PSCs) are among the most promising photovoltaic technologies owing to their exceptional optoelectronic properties^1,2. However, the lower efficiency, poor stability and reproducibility issues of large-area PSCs compared with laboratory-scale PSCs are notable drawbacks that hinder their commercialization³. Here we report a synergistic dopant-additive combination strategy using methylammonium chloride (MACl) as the dopant and a Lewis-basic ionic-liquid additive, 1,3-bis(cyanomethyl)imidazolium chloride ([Bcmim]Cl). This strategy effectively inhibits the degradation of the perovskite precursor solution (PPS), suppresses the aggregation of MACl and results in phase-homogeneous and stable perovskite films with high crystallinity and fewer defects. This approach enabled the fabrication of perovskite solar modules (PSMs) that achieved a certified efficiency of 23.30% and ultimately stabilized at 22.97% over a 27.22-cm² aperture area, marking the highest certified PSM performance. Furthermore, the PSMs showed long-term operational stability, maintaining 94.66% of the initial efficiency after 1,000 h under continuous one-sun illumination at room temperature. The interaction between [Bcmim]Cl and MACl was extensively studied to unravel the mechanism leading to an enhancement of device properties. Our approach holds substantial promise for bridging the benchtop-to-rooftop gap and advancing the production and commercialization of large-area perovskite photovoltaics.

Fig. 1. PSM structure and photovoltaic performance of the control and target PSMs.

a, Cross-sectional SEM image of the target device. Scale bar, 1 μm. b, Picture of one PSM. c, Distribution of short-circuit current (I_SC), V_OC, FF and PCE. d, Current–voltage (I–V) curves of three consecutive tests from forward and reverse scans for the certified PSM. e, Stabilized power output (SPO) performance of the certified PSM.

Fig. 2. ¹H NMR spectra of the PPS degradation at 60 °C for 24 h.

a, Control. b, Target. Key peaks from MFAI (2.78 ppm) and DMFAI (2.94 ppm) are highlighted. Spectra were recorded every 15 min in a mixture of d₆-DMSO:d₇-DMF with the ratio used for PSC fabrication and the intensity is normalized to the residual solvent peak (*). c, Mechanism of the [Bcmim]Cl-mediated stabilization of the PPS.

Fig. 3. NMR spectra of the interaction between [Bcmim]Cl and MACl.

a, ¹H NMR spectra of MACl solution as a function of concentration for four ionic liquids: [Bcmim]Cl, 1-cyanomethyl-3-methylimidazolium chloride ([Cmmim]Cl), 1,3-dimethylimidazolium chloride ([Dmim]Cl) and 1-butyl-3-methylimidazolium chloride ([Bmim]Cl). Full width at half maximum (FWHM) shift (b) and chemical shift of the MA⁺ NH peak as a function of ionic liquid/MACl concentration ratio (c).

Fig. 4. XRD patterns of the PTFs as a function of annealing time.

a, XRD patterns of the control PTF with only MACl as a function of annealing (100 °C) time. The peaks at 6.79° and 7.41° correspond to solvate phase S1 and the peak at 9.41° corresponds to solvate phase S2 (ref. ). The peaks located at 11.99°, 13.39° and 14.15° correspond to the 2H phase (δ phase), hexagonal phase (4H) and 3C phase (α phase), respectively. b, XRD patterns of the target PTF with both [Bcmim]Cl and MACl as a function of annealing (100 °C) time. c, XRD patterns of the PTF without MACl or [Bcmim]Cl as a function of annealing (100 °C) time. d, XRD patterns of the PTFs with only [Bcmim]Cl as a function of annealing (100 °C) time. e, XRD patterns of the PTFs after annealing at 100 °C for 60 min and at 150 °C for 10 min. The peak located at 12.70° corresponds to the (001) peak of PbI₂. a.u., arbitrary units.

Fig. 5. Secondary electron images with corresponding compositional mapping of PTFs by HIM-SIMS imaging.

Negative-mode (a) and positive-mode (b) SIMS polarity imaging of PTFs without annealing. Negative-mode (c) and positive-mode (d) SIMS polarity imaging of PTFs annealed at 100 °C for 60 min then at 150 °C for 10 min. SE, secondary electron. Scale bars, 1 µm.