One-Year stable perovskite solar cells by 2D/3D interface engineering

Abstract

Despite the impressive photovoltaic performances with power conversion efficiency beyond 22%, perovskite solar cells are poorly stable under operation, failing by far the market requirements. Various technological approaches have been proposed to overcome the instability problem, which, while delivering appreciable incremental improvements, are still far from a market-proof solution. Here we show one-year stable perovskite devices by engineering an ultra-stable 2D/3D (HOOC(CH₂)₄NH₃)₂PbI₄/CH₃NH₃PbI₃ perovskite junction. The 2D/3D forms an exceptional gradually-organized multi-dimensional interface that yields up to 12.9% efficiency in a carbon-based architecture, and 14.6% in standard mesoporous solar cells. To demonstrate the up-scale potential of our technology, we fabricate 10 × 10 cm² solar modules by a fully printable industrial-scale process, delivering 11.2% efficiency stable for >10,000 h with zero loss in performances measured under controlled standard conditions. This innovative stable and low-cost architecture will enable the timely commercialization of perovskite solar cells.

Figure 1. Optical and Structural characterization.

(a) Absorption spectra of the (HOOC(CH₂)₄NH₃)₂PbI₄ (blue dashed line), 3D CH₃NH₃PbI₃ (black line) and 2D/3D (red line) using 3% of HOOC(CH₂)₄NH₃I, AVAI hereafter. In the inset the intensity of the peak at 420 nm with increasing the percentage of AVAI to PbI₂. (b) Raman spectra for 100%AVAI (panel I.), 3%AVAI (panel II) and 0%AVAI (panel III) perovskites. Solid lines represent the fit from multi-gaussian peaks fitting procedure (Supplementary Fig. 3 for details). For 3D perovskite main peak at: 78, 109 and 250 cm⁻¹; for 2D at: 73, 109, 143, 171 cm⁻¹ and for 2D/3D at: 62, 87, 112, 143, 169 cm⁻¹; (c) X-Ray diffraction pattern of 100%AVAI (panel I); 3%AVAI (panel II) and 0%AVAI (panel III) perovskite. Peaks denoted with a star originate from the FTO/TiO₂ substrate. (d) Zoom of the X-ray diffraction pattern comparing the 3%AVAI with the pure 0%AVAI perovskites at selected angles. Substrate: mesoporous TiO₂.

Figure 2. Emission Properties.

(a) PL spectra, excitation at 400 nm, for the 100% HOOC(CH₂)₄NH₃I, AVAI hereafter and 2D/3D at 3%AVAI, exciting from the TiO₂ side, where perovskite is infiltrated within the mesoporous scaffold. (b) Normalized PL spectra, excitation at 600 nm, for the 2D/3D at 3% AVAI exciting from the top perovskite layer and from the TiO₂ side, where perovskite is infiltrated within the mesoporous scaffold compared to 3D 0%AVAI exciting from the mesoporous side (solid line). Since the light penetration depth is <100 nm at 600 nm, excitation of the perovskite film from the oxide side (scaffold thickness of around 1 μm) interrogates the perovskite nano-crystallites grown within the scaffold, while excitation from the perovskite top layer probes the intrinsic properties of the bulk perovskite growing on top. (c) PL dynamics of the bulk perovskite (exciting from the top layer) at 760 nm and from the oxide side at 730 nm of the 3%AVAI deposited on the insulating ZrO₂ mesoporous substrate.

Figure 3. First principles simulations of the 2D/3D interface.

(a) Local density of state (DOS) of the 3D/2D interface and (b) interface structure with the 2D phase contacting the TiO₂ surface. (c) Partial DOS summed on the 2D and 3D fragments calculated by including spin-orbit-coupling (SOC, inset) and without it. Notice the favourable alignment of conduction band states for electron injection into the 2D perovskite and possibly further into TiO₂.

Figure 4. 2D/3D Mesoporous Solar cell characteristics and stability.

(a) Device cartoon of the Hole transporting Material (HTM)-free solar cell and of the standard HTM-based solar cell. (b) Current density voltage (J–V) curve using the 2D/3D perovskite with 3% HOOC(CH₂)₄NH₃I, AVAI hereafter, in a standard mesoporous configuration using 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD)/Au (devise statistics and picture of the cell in the inset). (c) Stability curve of the Spiro-OMeTAD/Au cell comparing standard 3D with the mixed 2D/3D perovskite at maximum power point under AM 1.5G illumination, argon atmosphere and stabilized temperature of 45 °C. Solid line represent the linear fit. In the inset the champion device parameters are listed.

Figure 5. 2D/3D Carbon based Solar cell characteristics and stability.

(a) J–V curve using the 2D/3D perovskite with 3%AVAI in HTM-free solar cell measured under Air Mass (AM) 1.5G illumination (device statistics and picture in the inset). (b) J–V curve using the 2D/3D perovskite with 3%AVAI in a HTM-free 10 × 10 cm² module (device statistics and picture in the inset). (c) Typical module stability test under 1 sun AM 1.5 G conditions at stabilized temperature of 55° and at short circuit conditions. Stability measurements done according to the standard aging conditions. In the inset device parameters of the devices represented in a and b. Champions devices reported in Supplementary Table 2.