Tailoring nanoscale interfaces for perovskite–perovskite–silicon triple-junction photo voltaic cells

Supplies

Formamidinium iodide (FAI), formamidinium bromide (FABr), methylammonium iodide (MAI) and PDCl have been sourced from GreatCell Photo voltaic Supplies. Lead iodide (PbI₂), lead bromide (PbBr₂), rubidium iodide (RbI) and MeO-2PACz have been bought from Tokyo Chemical Business. BCP was bought from Lumtec. C₆₀ was bought from Nano C. Tetrakis(dimethylamino)tin(IV) (TDMASn) was bought from Strem Chemical compounds. Gold, copper and silver shot have been bought from ESPI Metals. Different dry chemical compounds have been bought from Sigma-Aldrich and all solvents have been bought from Alfa Aesar. Pre-patterned indium tin oxide (ITO) glasses with a sheet resistance of 8 Ω sq⁻¹ have been bought from Wuhan Jinge Photo voltaic Power Know-how.

Machine fabrication

For the fabrication of the silicon heterojunction backside photo voltaic cell, 6-inch N-type polished Czochralski wafers with a thickness of 150 μm and a resistivity starting from 1 to five Ω cm have been used. A wet-chemical course of, together with saw-damage elimination and cleansing, was utilized to the as-cut wafers. No texturing course of was used for this wafer. Subsequently, an intrinsic a-Si:H passivation layer (~5 nm) was first deposited by plasma-enhanced chemical vapour deposition (PECVD) on each side of the wafer. Then, n-type (~5 nm) and p-type (~8 nm) a-Si:H layers have been sequentially deposited at the back and front sides of the wafer, respectively. After PECVD, the again contact of the silicon cells was fabricated by stacking sputtered ITO (80 nm) after which thermally evaporated Ag by way of a shadow masks with a gap of 1.1 × 1.1 cm² or 4.1 × 4.1 cm² on the rear facet. For the entrance facet, a 20-nm-thick ITO layer was deposited on the n entrance facet by way of a shadow masks of 1.1 × 1.1 cm² or 4.1 × 4.1 cm², defining the aperture space of the silicon backside cell and appearing as a recombination layer between the silicon backside cell and the perovskite center cell. The silicon backside cells have been then laser-cut to a 2 × 2 cm² or 5 × 5 cm² sq. substrate for small-area (1 cm²) and large-area (16 cm²) tandem fabrication.

The 1.55-eV center perovskite has the construction: MeO-2PACz/Cs_0.08Rb_0.02FA_0.9PbI₃/ C₆₀/SnO₂/Au.

The entrance of the silicon photo voltaic cell was first handled with ultraviolet–ozone (UVO) cleaner for five min. This was adopted by deposition of the opening transport layer MeO-2PACz (0.5 mg ml⁻¹ in menthol) through spin-coating at 4,000 rpm for 20 s, adopted by annealing at 95 °C for 10 minutes. The 1.5 M Cs_0.08Rb_0.02FA_0.9PbI₃ precursor was then spin-coated at 2,000 rpm for 20 s, adopted by 6,000 rpm for 30 s. N₂ was blown onto the floor within the final 20 s earlier than the top of the spin course of. The movie was annealed at 105 ^oC for 10 min, producing a deep, darkish, dense perovskite movie. The substrates have been then transferred right into a thermal evaporation chamber for 20 nm C₆₀ deposition. This was adopted by 20-nm SnO₂ deposition by thermal ALD in an Arradiance GEMStar reactor. TDMASn was used because the Sn precursor and was held at 60 °C in a stainless-steel container. Water was used as an oxidant and was delivered from a stainless-steel container at room temperature, and the precursor supply manifold temperature was set to 115 °C. The TDMASn/purge1/H₂O/purge2 instances have been 1 s/10 s/0.2 s/15 s with corresponding nitrogen flows of 30 sccm/90 sccm/90 sccm/90 sccm to the deposition chamber at 80 °C. A 20-nm tin oxide layer was shaped after 135 cycles. After that, Au was deposited through thermal evaporation for various durations. Nominal thickness studying at 0, 0.2, 0.4, 0.6, 0.8 and 1 nm (utilizing the Inficon quartz crystal monitor with corrected tooling issue for gold materials) was used to differentiate completely different deposition instances.

The 1.91-eV prime perovskite cell had the construction: NiO_x/MeO-2PACz/Cs_0.16Rb_0.04FA_0.8Pb(I_0.45Br_0.55)₃/(PDCl)/C₆₀/SnO₂/Ag/MgF₂. The ten-nm NiO_x was deposited by sputter-coating utilizing a 2-inch goal underneath 60-W radiofrequency energy in Ar at 2 mTorr utilizing an AJA Worldwide sputtering system. The identical focus of MeO-2PACz was used as above for deposition, apart from an extended period of 30 s adopted by annealing at the next temperature of 100 °C. A 0.8 M, wide-bandgap perovskite precursor was then spin-coated utilizing a single-step spin programme (3,000 rpm for 50 s), with nitrogen fuel blown onto the floor over the past 25 s of the spin course of. The ensuing movie was annealed at 105 °C for 10 min, yielding a deep crimson, dense movie. The worth of x in Cs_0.2−xRb_xFA_0.8Pb(I_0.45Br_0.55)₃ was allowed to differ between 0 and 0.12 for optimizing perovskite movie high quality and system efficiency. The outcomes may be present in Supplementary Figs. 1 and 2. For the PDCl-treated perovskite, an answer of PDCl (~0.1 mg ml⁻¹ in isopropyl alcohol) was spin-coated onto the perovskite floor at 5,000 rpm for 20 s, adopted by annealing at 105 °C for an additional 10 min. The identical circumstances have been used for the deposition of C₆₀ and SnO₂ as above. Lastly, the 90 nm ITO clear electrode was deposited by sputter-coating by way of a metallic masks with an space of 1.1 × 1.1 cm² or 4.1 × 4.1 cm² with a 35-W radiofrequency energy and Ar at 1.5 mTorr utilizing the AJA Worldwide sputtering system. To finish triple-junction cell fabrication, the silver grid was deposited by thermal evaporation to a thickness of 230 nm and 720 nm, for 1 cm² and 16 cm², respectively, by way of a masks. Lastly, the entrance of the cell was deposited with 100 nm MgF₂ for antireflection.

For course of optimizations, 1.91-eV perovskite single-junction opaque cells and perovskite–perovskite double-junction semitransparent check cells have been additionally fabricated on glass substrates.

The patterned ITO-coated glass was first ready by ultrasonic cleansing in deionized water containing 2% Hellmanex, adopted by rinses in deionized water, acetone and isopropanol, every for 15 min. The cleaned ITO substrates have been then subjected to UVO remedy for 15 min. After UVO remedy, the substrates have been transferred to a nitrogen-filled glovebox for subsequent perovskite or perovskite–perovskite check photo voltaic cell fabrication.

The 1.91-eV perovskite single-junction opaque photo voltaic cell has the construction: glass/ITO/MeO-2PACz/Cs_0.16Rb_0.04FA_0.8Pb(I_0.45Br_0.55)₃/(PDCl)/C₆₀/BCP/Cu.

To judge the operational stability of Rb and MA incorporation in perovskites, three completely different compositions have been utilized in fabrication check cells with the construction glass/ITO/MeO-2PACz/perovskite/C₆₀/BCP/Cu. The three compositions have been:

1. (1)

   Cs_0.16Rb_0.04FA_0.8Pb(I_0.45Br_0.55)₃ (CsFARb);

2. (2)

   Cs_0.16MA_0.04FA_0.8Pb(I_0.45Br_0.55)₃ (CsFAMA);

3. (3)

   Cs_0.2FA_0.8Pb(I_0.45Br_0.55)₃ (CsFA).

The identical circumstances have been used as for the 1.55-eV center perovskite cell for the deposition of MeO-2PACz. The identical circumstances have been additionally used as above for the deposition of 1.91-eV perovskite, PDCl remedy and C₆₀. As a substitute of SnO₂, 7 nm BCP was deposited through thermal evaporation. Lastly, 100-nm-thick copper electrodes have been deposited by way of a metallic masks (to an outlined system aperture space of 0.0706 cm²) by thermal evaporation, to complete the single-junction perovskite photo voltaic cell fabrication.

The 1.55-eV perovskite–1.91-eV perovskite semitransparent tandem check cells have been fabricated utilizing the identical circumstances as these used for triple-junction cells, besides the Si backside cell was changed by ITO-patterned glass and the cell aperture space was 0.09 cm² and no metallic grid was deposited. Electrical contact was made on to the ITO.

Machine encapsulation

For stability exams, 1-cm² tandem units have been laminated between two items of 3-mm-thick glass laminated by clear polyolefin-type materials, with polyisobutylene utilized on the edges for sealing⁷. The laminating course of was carried out in a Radiant YDS-1111 laminator at 110 °C for 10 min at 800 millibars of stress. Copper tape was employed to ascertain electrical contact with the system electrodes, extending outward from the duvet glass.

Characterizations

J–V measurements for single-junction opaque units and perovskite–perovskite semitransparent double-junction units have been carried out utilizing a 1 lamp photo voltaic cell I–V testing system utilizing a category AAA photo voltaic simulator underneath an illumination energy of 100 mW cm⁻². The sunshine was calibrated utilizing an authorized reference cell. A scan fee of 100 mV s⁻¹ was used throughout measuring, sweeping from near-open circuit voltage (V_OC) (1.4 V for single junctions, 2.3 V for perovskite–perovskite tandems) to near- quick circuit present density (J_SC) (−0.1 V). Apertures of 0.0706 cm² and 0.09 cm² have been used for single-junction opaque cells (illuminated from the glass facet) and semitransparent double-junction cells (illuminated from the low-bandgap facet), respectively.

J–V measurements for 1-cm² triple-junction units have been carried out utilizing an LED photo voltaic simulator (6,060 A, 350–1,200 nm, AAA class, Qingdao Photo voltaic Science Instrument Hightech) underneath an illumination energy of 100 mW cm⁻². A scan fee of 100 mV s⁻¹ was used throughout measurement, sweeping from 3.2 V to close J_SC (−0.1 V). An aperture of 1.0 cm² was used. J–V measurements for 16 cm² triple-junction units have been carried out by the Shanghai Institute of Microsystem and Data Know-how, Chinese language Academy of Science, utilizing a twin gentle supply AAA steady-state photo voltaic simulator (YSS-T155A-2M) underneath an illumination energy of 100 mW cm⁻² with an aperture of 16.0 cm².

EQE measurements for single-junction photo voltaic cells have been carried out utilizing the QuantX-300 Spectral Response (Newport) system with monochromatic gentle from a xenon arc lamp.

EQE measurements for triple-junction tandem photo voltaic cells have been carried out in AC mode utilizing Enli Know-how (mannequin QE-R) Taiwan system. The EQE response was calibrated utilizing an authorized reference cell for 300–1,100 nm. For measuring EQE of the silicon backside cell, a blue LED (450 nm) and infrared LED (730 nm) have been used to saturate the highest and the center cells. For measuring EQE of the center perovskite cell, a blue LED (450 nm) and near-infrared LED (940 nm) have been used to saturate the highest and the underside cells. For measuring EQE of the highest perovskite cell, an infrared LED (730 nm) and near-infrared LED (940 nm) have been used to saturate the center and the underside cells.

Transient photocurrents of photo voltaic cells have been measured utilizing a Keysight MSO9254A oscilloscope. The 520 nm wavelength excitation gentle was offered by a Thorlabs NPL52B pulsed laser with a 5-ns pulse width, repetition fee of 1 MHz and pulse vitality of 1.2 nJ. The diameter of the beam was roughly 2 mm.

Temperature-dependent open circuit voltages of photo voltaic cells have been measured utilizing a Keysight 2636B supply meter, illuminated by a Thorlabs OSL2 Fiber-Coupled Illuminator with depth equal to 1 Solar. The temperature was managed utilizing a cryogenic cryogen-free variable temperature cryostat, with a Lakeshore 350 temperature controller.

The transmittance and reflectance of samples have been measured utilizing a Perkin Elmer Lambda1050 UV/Vis/NIR spectrophotometer.

Absorbances of samples have been measured utilizing an FS 5 (Edinburgh Devices).

Thermal admittance spectroscopy and Mott–Schottky have been carried out utilizing a Keysight E4990A impedance analyser, working from 20 Hz to 10 MHz with the ‘enhanced measurement pace’ possibility.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was carried out utilizing an IONTOF TOF-SIMS 5 system, working in constructive polarity mode with Bi³⁺ main ions at an vitality of 30 keV and Cs⁺ sputtering ions at 1 keV, within the MC^s+ operational mode

X-ray diffraction patterns have been recorded utilizing a Bruker ECO D8 diffractometer with a CuOkayα (λ = 1.5418 Å) radiation.

XPS and UPS have been carried out utilizing an ESCALAB250Xi (Thermo Scientific). For XPS evaluation, we employed X-ray emission utilizing an anode with MgOkayα line (12 kV–200 W) from an ultrahigh vacuum non-monochromatic supply. Following an preliminary survey scan to evaluate chemical states, we carried out high-resolution scans at a move vitality of 10 eV. The excitation vitality used was 1,253.6 eV. The Φ was calculated in accordance with the formulation Φ = hν (21.22 eV) − E_{cutoff-measured}.

High-view and cross-sectional SEM photographs have been obtained utilizing a field-emission microscope (NanoSEM 230).

TEM together with specimen preparation

To characterize gold Au deposited (for various durations) on the ALD SnO₂ layer, a carbon-coated TEM grid (EMSCF200-CU-UL, Proscitech) was used, which was coated with a 20-nm SnO₂ layer by ALD, adopted by thermal evaporation of Au for various instances.

The samples have been launched right into a JEOL 2100F FEG-TEM, which was fitted with a Gatan Ultrascan digicam for imaging. For the TEM imaging course of, we utilized an electron dose fee of roughly 2 e/Ų per second.

Photoluminescence characterizations

Regular-state photoluminescence spectra of perovskite movies have been measured utilizing an FS 5 (Edinburgh Devices) with an excitation wavelength of 450 nm.

For TRPL decay measurements, a LabRAM HR Evolution system was used with a time-correlated single photon counting system (DeltaPro-DD, Horiba). Utilizing a 485-nm diode laser (DD-510L, Horiba) because the excitation supply, a laser with a pulse period of 110 picoseconds, a reception fee of 312.5 kilohertz and a fluence of roughly 5–6 microjoules per sq. centimetre per pulse was used. The PL sign was captured at a wavelength of 660 nm. Each the incident and mirrored gentle have been directed by way of a ×50 goal lens (Leica PL FLUOTAR L 50/0.55), leading to a spot dimension of roughly 2 μm. The samples have been maintained in a nitrogen surroundings to stop degradation throughout the measurement course of. To find out the PL lifetime from the TRPL decay curves, a bi-exponential mannequin was utilized:

the place A₁ and A₂ are weightings of the τ₁-fast decay element recombination through defect trapping and of the τ₂-slow decay element related to radiative recombination¹⁵ was utilized in decay evaluation software program to suit the experimental outcomes. The typical lifetime, τ_avg was calculated utilizing the next equation:

For PL imaging, a customized PL imaging system, that includes 430-nm royal-blue LED chips and 451/106-nm bandpass filters, was employed. The cells have been secured in a nitrogen-filled, temperature-controlled customized jig throughout the imaging course of and uncovered to an depth equal to 1 Solar. To seize the PL picture, a Peltier-cooled (at −70 °C) Si CCD digicam from Princeton Devices (mannequin Pixis 1024) together with a 700-nm long-pass filter was used, with an publicity time of 0.03 s. The PL picture was then processed utilizing Fiji software program, which was additionally used so as to add a color bar and calibration bar to the picture.

Stability testing

For MPPT of the photo voltaic cells to judge operational stability of triple-junction tandems, encapsulated units have been positioned inside an environmental chamber for steady Xe illumination (100 mW cm⁻²). The temperature and relative humidity have been stored at 25 ± 5°C and 60 ± 20%, respectively. The MPPT algorithm relies on the well-established perturb-and-observe methodology, built-in right into a LabVIEW program for environment friendly implementation. The algorithm begins by deriving an preliminary estimation of the MPP by way of a fast preliminary J–V measurement. Within the common operation of the algorithm, the utilized voltage is perturbed utilizing a double step of each +10 mV and −10 mV across the voltage akin to the utmost energy level, denoted as V_MPP. Subsequently, the output energy of the photo voltaic cell is measured at these three distinct voltage ranges. The algorithm then selects the brand new V_MPP on the premise of the voltage configuration that yields the best energy output. One important facet of the algorithm’s execution is the period of every voltage step. It’s crucial to make sure that this period is sufficiently lengthy to permit for transients throughout the system to equilibrate earlier than computing the facility on the newly set voltage degree. This cautious consideration ensures the accuracy and effectiveness of the MPPT course of.

For IEC 61215 normal thermal biking testing, the encapsulated triple-junction tandem system underwent a thermal biking regime and was measured ex situ frequently. The temperature cycle was between −40 °C and 85 °C, and for 204 instances, on this work. In the course of the cyclic testing, the system was held at each −40 °C and 85 °C for a period of 10 min every. The temperature transitions between these factors have been executed at a managed ramp fee of 45 °C per hour.

Simulation

Simulation of the electrostatic floor potential of PD⁺ was carried out by the DFT/B3LYP methodology with a foundation set of 6-31G(d)(p) for figuring out the dipole second. All of the calculations have been carried out utilizing the Gaussian 16 program bundle.

A business software program bundle, Silvaco expertise computer-aided design, was used to mannequin the vitality band construction of the SnO₂/(Au)/NiO_x stack underneath thermal equilibrium.

To calculate the optical impact of the Au nanoparticles, the Python-based software program RayFlare²⁸ was used, which makes use of a modified model of the solver S⁴ (ref. ²⁹). The nanoparticles have been represented as Au pillars in an NiO_x background materials. It’s assumed that the nominal thickness of Au (d_Au,nominal) deposited can be utilized to calculate the whole quantity of Au deposited per unit space, in order that the peak of the Au pillars (h_pillar) may be calculated from h_pillar = d_Au,nominal/C, the place C is the world protection fraction of the Au. The protection fraction was decided from scanning TEM photographs of Au deposited at completely different nominal thicknesses. Since RCWA calculations assume a periodic unit cell, the random construction of the Au nanoparticles was simulated by producing a random unit cell, containing eight non-overlapping Au pillars randomly positioned throughout the unit cell. The radius of the discs and dimension of the unit cell have been chosen to present the proper protection fraction with the pillar top as calculated above. The cell construction used is proven in Fig. 3a. Twenty random unit cells have been generated for every protection fraction, with the reflectance, transmittance and absorptance per layer calculated for every distinctive unit cell assuming usually incident unpolarized gentle. We then took the typical of those outcomes. The utmost potential quick circuit present of the 2 perovskite junctions was calculated as:

the place Φ_AM1.5G(λ) is the photon flux within the AM1.5G photo voltaic spectrum as a operate of wavelength, q is the elementary cost and A_i(λ) is the fraction of incident photons absorbed within the related perovskite layer, from the typical of the 20 randomly generated unit cells. For the outcomes with out antireflection coating, the simulations have been carried out utilizing RCWA solely. To simulate cells with textured polydimethylsiloxane antireflection coating, RayFlare’s ray tracer was used, assuming an everyday inverted pyramid construction with a gap angle of 52°.

Simulation codes for ends in Supplementary Figs. 18–21 may be present in ref. ³⁰.

Reporting abstract

Additional info on analysis design is offered within the Nature Portfolio Reporting Abstract linked to this text.