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

Supplies

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

Gadget 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 had been used. A wet-chemical course of, together with saw-damage removing 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 either side of the wafer. Then, n-type (~5 nm) and p-type (~8 nm) a-Si:H layers had 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 via a shadow masks with a gap of 1.1 × 1.1 cm² or 4.1 × 4.1 cm² on the rear aspect. For the entrance aspect, a 20-nm-thick ITO layer was deposited on the n entrance aspect via 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 had 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) by way of 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 had 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 occasions had 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 by way of 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 tell apart totally different deposition occasions.

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 length of 30 s adopted by annealing at a better 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 purple, dense movie. The worth of x in Cs_0.2−xRb_xFA_0.8Pb(I_0.45Br_0.55)₃ was allowed to range between 0 and 0.12 for optimizing perovskite movie high quality and gadget efficiency. The outcomes might 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 one more 10 min. The identical circumstances had been used for the deposition of C₆₀ and SnO₂ as above. Lastly, the 90 nm ITO clear electrode was deposited by sputter-coating via 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, via 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 had 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 had been then subjected to UVO remedy for 15 min. After UVO remedy, the substrates had 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 totally different compositions had been utilized in fabrication check cells with the construction glass/ITO/MeO-2PACz/perovskite/C₆₀/BCP/Cu. The three compositions had 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 had been used as for the 1.55-eV center perovskite cell for the deposition of MeO-2PACz. The identical circumstances had 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 by way of thermal evaporation. Lastly, 100-nm-thick copper electrodes had been deposited via a metallic masks (to an outlined gadget 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 had 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.

Gadget encapsulation

For stability assessments, 1-cm² tandem gadgets had 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 strain. Copper tape was employed to determine electrical contact with the gadget electrodes, extending outward from the duvet glass.

Characterizations

J–V measurements for single-junction opaque gadgets and perovskite–perovskite semitransparent double-junction gadgets had 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 price 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 had been used for single-junction opaque cells (illuminated from the glass aspect) and semitransparent double-junction cells (illuminated from the low-bandgap aspect), respectively.

J–V measurements for 1-cm² triple-junction gadgets had 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 price 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 gadgets had been carried out by the Shanghai Institute of Microsystem and Data Know-how, Chinese language Academy of Science, utilizing a twin mild 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 had been carried out utilizing the QuantX-300 Spectral Response (Newport) system with monochromatic mild from a xenon arc lamp.

EQE measurements for triple-junction tandem photo voltaic cells had 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) had 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) had 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) had been used to saturate the center and the underside cells.

Transient photocurrents of photo voltaic cells had been measured utilizing a Keysight MSO9254A oscilloscope. The 520 nm wavelength excitation mild was supplied by a Thorlabs NPL52B pulsed laser with a 5-ns pulse width, repetition price 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 had 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 had been measured utilizing a Perkin Elmer Lambda1050 UV/Vis/NIR spectrophotometer.

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

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

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⁺ major ions at an vitality of 30 keV and Cs⁺ sputtering ions at 1 keV, within the MC^s+ operational mode

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

XPS and UPS had been carried out utilizing an ESCALAB250Xi (Thermo Scientific). For XPS evaluation, we employed X-ray emission utilizing an anode with MgOkα 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 go vitality of 10 eV. The excitation vitality used was 1,253.6 eV. The Φ was calculated in accordance with the method Φ = hν (21.22 eV) − E_{cutoff-measured}.

Prime-view and cross-sectional SEM photos had 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 occasions.

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

Photoluminescence characterizations

Regular-state photoluminescence spectra of perovskite movies had 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 length of 110 picoseconds, a reception price 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 mild had been directed via a ×50 goal lens (Leica PL FLUOTAR L 50/0.55), leading to a spot measurement of roughly 2 μm. The samples had been maintained in a nitrogen setting to forestall degradation through 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 part recombination by way of defect trapping and of the τ₂-slow decay part related to radiative recombination¹⁵ was utilized in decay evaluation software program to suit the experimental outcomes. The common 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 had been secured in a nitrogen-filled, temperature-controlled customized jig through 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 digital camera 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 guage operational stability of triple-junction tandems, encapsulated gadgets had been positioned inside an environmental chamber for steady Xe illumination (100 mW cm⁻²). The temperature and relative humidity had 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 via a speedy 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 idea of the voltage configuration that yields the best energy output. One important side of the algorithm’s execution is the length of every voltage step. It’s crucial to make sure that this length is sufficiently lengthy to permit for transients throughout the system to equilibrate earlier than computing the ability on the newly set voltage degree. This cautious consideration ensures the accuracy and effectiveness of the MPPT course of.

For IEC 61215 commonplace thermal biking testing, the encapsulated triple-junction tandem gadget underwent a thermal biking regime and was measured ex situ repeatedly. The temperature cycle was between −40 °C and 85 °C, and for 204 occasions, on this work. Through the cyclic testing, the gadget was held at each −40 °C and 85 °C for a length of 10 min every. The temperature transitions between these factors had been executed at a managed ramp price 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 had been carried out utilizing the Gaussian 16 program package deal.

A industrial software program package deal, Silvaco know-how 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 had 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 overall quantity of Au deposited per unit space, in order that the peak of the Au pillars (h_pillar) might be calculated from h_pillar = d_Au,nominal/C, the place C is the realm protection fraction of the Au. The protection fraction was decided from scanning TEM photos of Au deposited at totally 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 measurement of the unit cell had been chosen to provide the right protection fraction with the pillar top as calculated above. The cell construction used is proven in Fig. 3a. Twenty random unit cells had been generated for every protection fraction, with the reflectance, transmittance and absorptance per layer calculated for every distinctive unit cell assuming usually incident unpolarized mild. We then took the common of those outcomes. The utmost attainable 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 common of the 20 randomly generated unit cells. For the outcomes with out antireflection coating, the simulations had been carried out utilizing RCWA solely. To simulate cells with textured polydimethylsiloxane antireflection coating, RayFlare’s ray tracer was used, assuming a daily inverted pyramid construction with a gap angle of 52°.

Simulation codes for leads to Supplementary Figs. 18–21 might be present in ref. ³⁰.

Reporting abstract

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