Promising Power Conversion Efficiency Research Articles

Suppressing Nonradiative Recombination in Lead–Tin Perovskite Solar Cells through Bulk and Surface Passivation to Reduce Open Circuit Voltage Losses

Lead–Tin perovskite solar cells (Pb/Sn PSCs) are limited by the intrinsic instability of Sn(II), which tends to oxidize forming Sn vacancies in perovskite films. Herein, a Lewis base β-guanidinopropionic acid (GUA) and hydrazinium iodide (HAI) are introduced to effectively passivate the perovskite bulk and surface, respectively. The synergistic approach leads to Pb/Sn PSCs with a promising power conversion efficiency of 20.5% owing to the significantly reduced nonradiative recombination and voltage losses. As a result, the VOC × FF product of PSCs is significantly improved, which is among the highest values documented in the literature, being favorable for perovskite-based tandem applications. Additionally, the strategy demonstrated in this work could also improve the stability of PSCs by enhancing the chemical robustness of the perovskite layer. These results emphasize the significance of bulk and surface passivation in the development of efficient and stable PSCs based on Pb/Sn perovskites.

Panchromatic oxasmaragdyrin as dual functional hole‐transporting material in all‐inorganic CsPbIBr2 perovskite solar cells

AbstractAll‐inorganic perovskite CsPbIBr2 offers both an optimal bandgap and good stability. The perovskite solar cells (PSCs) with CsPbIBr2 as a solar harvester utilize mainly spiro‐OMeTAD as a hole‐transporting material (HTM). Still, these PSCs are prone to degradation and not cost‐effective. Herein we examined, for the first time, a metal‐free dimethoxyboranyl (B(OR)2) chelated oxasmaragdyrin, SM‐OMe, as an alternative bifunctional HTM for CsPbIBr2‐based PSCs to demonstrate promising power conversion efficiencies at lower costs. The devices with SM‐OMe as HTM outperform spiro‐OMeTAD‐based devices with the highest power conversion efficiency of 6.04%. This enhanced performance can be attributed to an HTM and sensitizer dual‐function of SM‐OMe, which extends the absorption edge and consequently improves the short circuit current density. Furthermore, SM‐OMe‐based devices exhibited better charge extracting and hole‐transporting properties. Hence, this study demonstrates an effective and successful utilization of a new HTM with a bifunctional role as an alternative to conventional spiro‐OMeTAD in all‐inorganic PSCs.

Modulating the nanoscale morphology on carboxylate-pyrazine containing terpolymer toward 17.8% efficiency organic solar cells with enhanced thermal stability

It had been commonly accepted in the organic photovoltaic (OPV) community that subtle variations in the molecular structure of active layer materials would cause profound impacts on their aggregating structure and blend morphology and therefore the performance of such polymer solar cells (PSCs). Herein, we employed an electron-deficient building block 3,6-dithiophenyl-2-carboxylate pyrazine (DTCPz) for constructing one series of promising donor terpolymers of PMZ1, PMZ2, and PMZ3, respectively, gaining their relatively lower-lying highest occupied molecular orbital (HOMO) energy levels, more closed π-π stacking and enhanced crystallinity in thin films, and lower miscibility with acceptor Y6, in comparison with their parent polymer counterpart (namely PM6). Reaching DTCPz moieties up to 20% (mol/mol%) in its terpolymer composition, the resulting polymer (PMZ2) achieved more favorable phase separation with improved exciton dissociation, and charge transport and extraction. As a result, an outstanding fill factor of 77.2% and a promising power conversion efficiency of 17.8 % was achieved. Moreover, the corresponding device shows better thermal stability over the PM6-based one. This work suggests a facile method for significantly improving the thin film morphology of the active-layer materials via fine-tuning the chemical structure of electron-deficient units on the backbone of the wide bandgap donor polymer, therefore achieving enhanced photovoltaic performance and thermal stability for practical applications.

Magnesium doped spinel NiCo2O4 for improved hole extraction in efficient inverted perovskite solar cells

In recent years, p-type oxide semiconductors have been widely used as hole transport materials (HTMs) in halide perovskite solar cells (PSCs). Spinel NiCo2O4 has attracted much attention in this regard due to its environmental friendliness and rich elemental composition. In this work, a solution-processed Mg-doped NiCo2O4 film was prepared for the first time as HTM for inverted planar PSCs. The density functional theory calculations reveal that the Mg doping increases the electronic states at the Fermi energy level of NiCo2O4 to promote the carrier transport. Ultraviolet photoelectron spectroscopy (UPS) further shows that the valance band maximum (VBM) of the Mg-doped NiCo2O4 is increased by 0.08 eV compared to that of pristine NiCo2O4, thus reducing the energy level mismatch at the HTM/perovskite interface. As a result, the Mg-doped NiCo2O4 HTM enables a promising power conversion efficiency (PCE) of 16.71% for the inverted MAPbI3 PSCs, which is 18% higher than that of the pristine NiCo2O4 devices (14.07%). The improved PCE is attributed to the improved hole extraction and better matching of the interfacial energy levels of the Mg-doped NiCo2O4. Our result provides novel prospect for the electronic structure manipulation of spinel NiCo2O4 by element doping.

Photovoltaic Performance of TiO2 Mesoporous Films with Different Working Areas for Dye-sensitized Solar Cells

The photovoltaic performance of Dye-sensitized Solar Cells (DSSC) could be optimized by playing the working area of the mesoporous TiO2 photoanode. A small working area will enhance the photovoltage and power conversion efficiency. In comparison, a large working area will improve the recombination rate and reduce the photon particle transport rate at the photoanode. The TiO2 based photoanode layer consists of a blocking layer and mesoporous paste deposited using spin coating and screen printing technique, respectively with various working areas of 0.25, 0.30, and 0.56 cm2. The cells were characterized using XRD, SEM-EDX, UV-Vis spectroscopy, and solar simulator. XRD confirmed that the TiO2 was in the anatase phase. SEM image represented a high surface area of mesoporous TiO2 indicated by porosity level up to 70%. The elemental analysis of TiO2 using EDX observed the presence of Ti and O peaks. The TiO2 mesoporous-based photoanode immersed in 0.07 mM of N719 solution possessed an absorbance range in the ultraviolet to the visible light. The working area of 0.25 cm2 exhibited a promising power conversion efficiency of 2.02% with a circuit current density of 10.8 mA/cm2 under an illumination light of 100 mW/cm2.

Numerical simulations of novel quaternary chalcogenide Ag2MgSn(S/Se)4 based thin film solar cells using SCAPS 1-D

This paper presents numerical simulation study of novel chalcogenide materials Ag2MgSnS4 and Ag2MgSnSe4 based thin film solar cells using SCAPS-1D simulation package. Effect of absorber layer properties such as thickness, doping density, defect density, and mobility on device performance have been optimized and analyzed in detail in this work. Also, thickness of buffer layer along with the effect of device series and shunt resistance have been studied on characteristic parameters of both the devices. A promising simulated power conversion efficiency of 19.2% and 21.35% have been obtained, respectively, for Ag2MgSnS4 and Ag2MgSnSe4 based devices. The values of built-in potential (BIP) have been estimated using capacitance voltage curve. Further, recombination coefficients at buffer/absorber interface, depletion region and quasi neutral region have also been calculated. The obtained values are compared with CZTS based TFSC and our calculated values outperform the conventional TFSC. Hence, our study will motivate researchers to fabricate the similar device.

Solvent-engineering-processed CsPbIBr2 inorganic perovskite solar cells with efficiency of ∼11%

Recently, the cesium lead halide perovskite (CsPbIBr2) materials demonstrating the most balanced bandgap and stability among all inorganic perovskite analogs have received great attention in photovoltaic community. However, the poor quality of solution-processed CsPbIBr2 films with small grains and massive voids and defects severely impedes its further development. This obstacle issue mainly roots from the slow crystallization process of perovskites when using traditional high boiling point solvent of dimethyl sulfoxide (DMSO). Herein, a novel solvent engineering strategy, namely alcohol-induced rapid crystallization process, is originally developed. We intentionally add some low boiling point alcohols, such as methanol, ethanol, isopropanol, and n-butanol, to form a lower boiling point DMSO-alcohol azeotropic mixture, which can be volatilized quickly and effectively accelerate the crystallization process of CsPbIBr2 films. Meanwhile, we elaborately adopt some CsI additives to suppress the intrinsic self-doping and passivate the defects of perovskites. Besides, the influence of annealing temperatures on the film quality and device performance is also investigated in this study. Consequently, the pinhole-free, highly crystallized CsPbIBr2 films with large grains and a preferable (100) orientation are successfully achieved via CsI/methanol treatment recipe when annealed at the optimized temperature of 280 °C. The as-obtained perovskite solar cells (PSCs) with a superior long-term stability feature yield a highly promising power conversion efficiency (PCE) of 11.49%. To our knowledge, this is the highest reported efficiency among all CsPbIBr2 inorganic PSCs.

Near-Infrared All-Fused-Ring Nonfullerene Acceptors Achieving an Optimal Efficiency-Cost-Stability Balance in Organic Solar Cells

Near-Infrared All-Fused-Ring Nonfullerene Acceptors Achieving an Optimal Efficiency-Cost-Stability Balance in Organic Solar Cells

Organic-semiconductor-assisted dielectric screening effect for stable and efficient perovskite solar cells

Perovskite solar cells (pero-SCs) performance is essentially limited by severe non-radiative losses and ion migration. Although numerous strategies have been proposed, challenges remain in the basic understanding of their origins. Here, we report a dielectric-screening-enhancement effect for perovskite defects by using organic semiconductors with finely tuned molecular structures from the atoms level. Our method produced various perovskite films with high dielectric constant values, reduced charge capture regions, suppressed ion migration, and it provides an efficient charge transport pathway for suppressing non-radiative recombination beyond the passivation effect. The resulting pero-SCs showed a promising power conversion efficiency (PCE) of 23.35% with a high open-circuit voltage (1.22 V); and the 1-cm2 pero-SCs maintained an excellent PCE (21.93%), showing feasibility for scalable fabrication. The robust operational and thermal stabilities revealed that this method paved a new way to understand the degradation mechanism of pero-SCs, promoting the efficiency, stability and scaled fabrication of the pero-SCs.

Restricting lithium-ion migration via Lewis base groups in hole transporting materials for efficient and stable perovskite solar cells

• Lewis base groups are introduced into HTMs to restrict ion migration of Li + . • Phen-TPA effectively restricts ion migration of Li + by strong coordination effect. • PSC based on Phen-TPA achieves a PCE of 20.02% with negligible hysteresis effect. • PSC based on Phen-TPA exhibits preferable humid and thermal stability. • The performance of PSCs is promoted with enhanced coordination ability of HTMs. Li-TFSI as an indispensable dopant for hole transporting materials (HTMs) suffers from inherent hydrophilicity and ion migration, which seriously damages the stability of perovskite solar cells (PSCs). Herein, a facile design strategy is proposed to restrict ion migration of Li + by introducing different Lewis base groups (pyridine, 1,10-phenanthroline and pyrazine) into HTMs. Owing to the coordination effect of Lewis base groups to Li + , the doped HTMs (Pyrd-TPA, Phen-TPA and Pyra-TPA) exhibit significantly enhanced conjugation and hole mobility. Particularly, theoretical calculation and Fourier-transform infrared spectroscopy (FTIR) results demonstrate that Phen-TPA forms the strongest coordination with Li + due to the most negative electrostatic potential region existing around 1,10-phenanthroline group. The generated Li + -coordinated Phen-TPA contributes to preferable energy levels, morphology uniformity and hydrophobicity. Element mapping analysis shows that Li-ion migration in doped Phen-TPA is restricted effectively. In addition, Phen-TPA can also passivate the perovskite surface defects dramatically, which facilitates more efficient charge transfer to hole transporting layer. Consequently, PSCs based on Phen-TPA achieve promising power conversion efficiency (PCE) of 20.02% with negligible hysteresis effect. More importantly, it maintains over 88% of the initial PCE after 1056 h storage in ambient condition of 40–60% RH and about 81% of the original efficiency after 264 h storage at 60–70 °C. This work systematically revealed the relation between coordination ability of HTMs and the performance of PSCs for the first time, which provides new design strategies to develop efficient and stable PSCs.

Palladium(II) and Platinum(II) Porphyrin Donors for Organic Photovoltaics

Three new A-π-D-π-A structural porphyrin-based donors, C19-H2P, C19-PdP, and C19-PtP, are designed and synthesized, with porphyrin (D) moieties equipped with no metal, palladium (Pd), and platinum (Pt) as the core, respectively, and end-capped with electron-deficient 3-ethylrhodanine (A) via a π-bridge of phenylene ethynylene linker. C19-PdP and C19-PtP exhibit low-lying highest occupied molecular orbital levels than C19-H2P. The three porphyrin donors show highly intensified and broad absorptions at ca. 400–530 nm (Soret bands) and at ca. 550–800 nm (Q-bands) with an absorption valley at ca. 540 nm. Using PC71BM as an electron acceptor, the devices based on C19-PdP and C19-PtP donors achieve power conversion efficiencies (PCEs) of 8.09 and 7.31% under 1 Sun, respectively, whereas the C19-H2P device, that has no metal, has a very low PCE of 2.51%. Furthermore, at 300 lux LED source, the C19-PdP and C19-PtP devices deliver promising PCEs of 16.54 and 16.74%, respectively. The improved performance of C19-PdP- and C19-PtP-based devices is mainly due to more efficient charge collection, faster charge transport, more suppressed recombination behavior, and smoother surface morphology. These findings pave the way for the development of new metalloporphyrin-based donors for organic solar cells using simple structural engineering.

Simple-Structured Low-Cost Dopant-Free Hole-Transporting Polymers for High-Stability CsPbI2Br Perovskite Solar Cells.

Among the solution-processed devices, perovskite solar cells (PSCs) exhibit the highest power conversion efficiency (PCE) of over 25%; tremendous efforts are being undertaken to improve their stability. Recently, all-inorganic CsPbI2Br-based PSCs were reported to exhibit a significantly improved device stability, with a promising PCE of up to 16.79%. In this study, we report stable all-inorganic PSCs by incorporating novel dopant-free hole-transporting materials (HTMs). The synthesis strategy of the newly synthesized polymeric HTMs was similar to that of 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD), with the exception that they were designed to exhibit dopant-free characteristics. In particular, their polymeric backbone structure was significantly simpler than that of spiro-OMeTADs, and they were easily synthesized in two steps from commercially available chemicals, with an overall yield of ∼50%. The cost of synthesis at the laboratory scale was calculated to be at least 2.4 times cheaper than that of spiro-OMeTADs. The PCE of dopant-free HTM-based PSCs was 11.01%, which is 1.5 times higher than that of the dopant-free spiro-OMeTAD-based devices (7.52%) and comparable to that of the doped spiro-OMeTAD-based devices (12.22%). Notably, the stability of the device based on our dopant-free HTM to atmospheric oxygen and moisture as well as heat and light irradiation was superior to that of devices based on doped and dopant-free spiro-OMeTAD HTMs. On consideration of the synthesis cost, device efficiency, and device stability, our dopant-free HTM is highly promising for all-inorganic PSCs.

High-Polarizability Organic Ferroelectric Materials Doping for Enhancing the Built-In Electric Field of Perovskite Solar Cells Realizing Efficiency over 24.

The built-in electric field (BEF) intensity of silicon heterojunction solar cells can be easily enhanced by selective doping to obtain high power conversion efficiencies (PCEs), while it is challenging for perovskite solar cells (pero-SCs) because of the difficulty in doping perovskites in a controllable way. Herein, an effective method is reported to enhance the BEF of FA0.92 MA0.08 PbI3 perovskite by doping an organic ferroelectric material, poly(vinylidene fluoride):dabcoHReO4 (PVDF:DH) with high polarizability, that can be driven even by the BEF of the device itself. The polarization of PVDF:DH produces an additional electric field, which is maintained permanently, in a direction consistent with that of the BEF of the pero-SC. The BEF superpositioncan more sufficiently drive the charge-carrier transport and extraction, thus suppressing the nonradiative recombination occurring in the pero-SCs. Moreover, the PVDF:DH dopant benefits the formation of a mesoporous PbI2 film, via a typical two-step processing method, thereby promoting perovskite growth with high crystallinity and a few defects. The resulting pero-SC shows a promising PCE of 24.23% for a 0.062 cm2 device (certified PCE of 23.45%), and a remarkable PCE of 22.69% for a 1 cm2 device, along with significantly improved moisture resistances and operational stabilities.

Porphyrin-Based All-Small-Molecule Organic Solar Cells With Absorption-Complementary Nonfullerene Acceptor

It is crucial to minimize the absorption overlap between donor and acceptor for high-efficiency all-small-molecule organic solar cells with high current densities. Considering strong absorption of nonfullerene acceptors 2,2.-((2Z,2?Z)-((4,4,9,9-tetrah exyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b.]dithiophene-2,7-diyl)bis (methanylylidene))bis(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (IDIC) in the ranges of 650–750 nm, two porphyrin unit-based small molecules containing diketopyrrolopyrrole groups (Dipor and Por) are selected as the electron donor materials because of their weak absorption in this region. Porphyrin dimer Dipor displays a broad photon response from 300 to 1000 nm in the films and its absorption deficiency between the Soret and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -bands could be perfectly compensated by nonfullerene acceptors IDIC, while monomer Por shows partial overlapping absorption to IDIC in ranges of 650–700 nm and its absorption edge locates at ∼900 nm. The higher compatibility of porphyrin dimer Dipor and IDIC results in a promising power conversion efficiency of 8.3% with a high short-circuit current density ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_sc</i> ) of 20.2 mA cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup> , whereas the devices based on Por: IDIC show a lower power conversion efficiency of 6.3%.

On the role of carboxylated polythiophene in defect passivation of CsPbI 2 Br surface for efficient and stable all‐inorganic perovskite solar cells

Improved film surface is a prerequisite to achieve high photovoltaic performance of inorganic perovskite solar cells because defective (under-coordinated) lead ions derived from imperfect lattice structure of the film surface or grain boundaries the principal nonradiative recombination centers in the inorganic perovskite absorber. In this study, we suggest poly[3-(4-carboxybutyl)thiophene-2,5-diyl] (P3CT), a carboxylated p-type conjugated polymer, as a passivating agent of the CsPbI2Br layer to tailor electronic properties of a perovskite absorber. With the P3CT passivation, the defective sites of the perovskite film surface were improved and stabilized, which can suppress nonradiative recombination to promote charge transport of CsPbI2Br-based all-inorganic perovskite solar cells. Consequently, the P3CT passivation delivers a power conversion efficiency (PCE) of 12.25% and decent long-term stability of CsPbI2Br perovskite solar cells, which surpasses the pristine device without the passivation. The electricity generation capability under indoor light source of the passivated device is also studied, demonstrating a promising PCE of 27.47%. This work unveils the role of P3CT as a passivating agent to passivate the defective sites of CsPbI2Br perovskite film surface and grain boundaries, which facilitates charge transport and reduced carrier recombination of CsPbI2Br absorber in solar cell devices.

Highly Semitransparent Indoor Nonfullerene Organic Solar Cells Based on Benzodithiophene‐Bridged Porphyrin Dimers

Two acceptor‐donor‐acceptor‐based porphyrin dimers, C8TEBDT‐2P and C8TBDT‐2P, are presented as donors for high‐performance semitransparent indoor organic photovoltaics. Both compounds vary in that benzodithiophene (BDT) bridged the two porphyrins at the meso‐carbon directly for the latter with a less planar structure, and via ethynylene for the former with a more planar structure. As a result, the C8TEBDT‐2P exhibits a more red‐shifted absorption profile from 400 to 800 nm than the C8TBDT‐2P from 400 to 700 nm due to stronger π‐conjugation. Using indaceno‐dithiophene‐indene‐dimalononitrile (IDIC) as a nonfullerene acceptor, the blend film C8TEBDT‐2P:IDIC shows a promising power conversion efficiency (PCE) of 12.3% under indoor (300 lux light‐emitting diode) and a PCE of 7.46% under one sun illuminations. The improved efficiency of the device C8TEBDT‐2P: IDIC is mainly due to highly ordered surface morphology, that leads in efficient charge separation, faster charge transport, and less charge recombination. Furthermore, the photopic properties indicate that both devices have good transparency and chromaticity, with an average visible transmittance value of 70% for C8TEBDT‐2P:IDIC and 73% for C8TBDT‐2P:IDIC. This study enriches the pool of porphyrin donors for highly semi‐transparent indoor nonfullerene organic solar.

Donor–Acceptor Type Polymer Bearing Carbazole Side Chain for Efficient Dopant‐Free Perovskite Solar Cells

AbstractIn conventional n–i–p perovskite solar cells (PVSCs), electron donor (D)–acceptor (A) polymers have been found to be potential substitutes for doped spiro‐based small molecule hole‐transporting materials (HTMs) due to their excellent performance in hole mobility, film formability, and stability. Herein, a benzo[1,2‐b:4,5‐b′]dithiophene (BDT)‐benzodithiophene‐4,8‐dione (BDD) copolymer PBDB‐Cz is developed by employing carbazole as the conjugated side chain of BDT. PBDB‐O and PBDB‐T with alkoxy and thiophene as the side chain of BDT, respectively, are also synthesized and studied for comparison. The synergistic effect of the carbazole side chain and the BDT‐BDD backbone to promote hole transport properties is found in PBDB‐Cz. The carbazole side chain enhances both coplanarity and interaction of polymer chains, while simultaneously deepening energy levels and improving the hole mobility of the polymeric HTM. Consequently, PBDB‐Cz outperforms two counterparts, exhibiting a promising power conversion efficiency (PCE) of 22.06%. Notably, the PBDB‐Cz also improves the device stability, and the devices can retain more than 90% of their initial PCEs after being stored at ambient conditions for 100 days. To the best of the authors’ knowledge, this is the first report to incorporate carbazole into D–A polymeric HTM by side chain engineering.

ZrSnO4: A Solution-Processed Robust Electron Transport Layer of Efficient Planar-Heterojunction Perovskite Solar Cells

A robust electron transport layer (ETL) is an essential component in planar-heterojunction perovskite solar cells (PSCs). Herein, a sol-gel-driven ZrSnO4 thin film is synthesized and its optoelectronic properties are systematically investigated. The optimized processing conditions for sol-gel synthesis produce a ZrSnO4 thin film that exhibits high optical transmittance in the UV-Vis-NIR range, a suitable conduction band maximum, and good electrical conductivity, revealing its potential for application in the ETL of planar-heterojunction PSCs. Consequently, the ZrSnO4 ETL-based devices deliver promising power conversion efficiency (PCE) up to 19.05% from CH3NH3PbI3-based planar-heterojunction devices. Furthermore, the optimal ZrSnO4 ETL also contributes to decent long-term stability of the non-encapsulated device for 360 h in an ambient atmosphere (T~25 °C, RH~55%,), suggesting great potential of the sol-gel-driven ZrSnO4 thin film for a robust solution-processed ETL material in high-performance PSCs.

Simple Additive to MAPbI3 Solution that Enhances Film Quality of Mini‐Module Perovskite Solar Cells Fabricated under Moderate Humidity

An additive to perovskite material can play a crucial role in the fabrication of perovskite solar cells (PSCs); the additive treatment investigated herein produces promising overall power conversion efficiency (PCE) enhancements. Currently, the fabrication of PSCs is mainly carried out under the dry air of a glove box to avoid moisture adsorption by methylammonium lead iodide perovskites; these tight restrictions in how PSCs are fabricated hinder the possibility of their commercialization. In this study, a technique that uses C12F4N4 as an additive to the MAPbI3 for the one‐step deposition of perovskite layers under moderate humidity is presented; this approach is able to achieve high‐quality perovskite films despite the adverse condition. The added C12F4N4 bridges the gaps between the MAPbI3 grain boundaries and significantly enhances all the photovoltaic parameters compared to using pristine methylammonium lead iodide; this method even eventually enhances the overall PCE. Both, single‐cell and optimized five‐cell integrated mini‐module devices in moderately humid conditions are fabricated. This facile method presents new possibilities for scaling up PSCs production in humid environments.

Surface Reconstruction for Stable Monolithic All‐Inorganic Perovskite/Organic Tandem Solar Cells with over 21% Efficiency

AbstractThe construction of monolithic two‐terminal tandem solar cells (2T TSCs) offers the possibility of pursuing high power conversion efficiency (PCE) by overcoming the single‐junction Shockley–Queisser limit in photovoltaics. However, little attention is paid to simultaneously improve the stability by utilizing the complementary properties of various photoactive layers. Here, beyond the stacked photoactive layers featuring complementary absorption, all‐inorganic perovskite (CsPbI1.8Br1.2) is chosen as the photoactive layer of the front wide‐bandgap subcell for its intrinsic high thermal stability and ultraviolet (UV)‐filtering function to address the burn‐in and UV degradation of organic rear subcells. To realize their monolithic integration, the charge recombination efficiency in the interconnecting layer (ICL) between the two types of subcells is tentatively improved by surface reconstruction of all‐inorganic perovskite using trimethylammonium chloride. The repaired CsPbI1.8Br1.2 surface enables effective suppression of nonradiative recombination and facilitates hole transport, providing efficient charge recombination in the ICL in the 2T TSC. As a result, the all‐inorganic perovskite/organic 2T TSC delivers a promising PCE of 21.04%, accompanied by an ultrahigh open‐circuit voltage (Voc) of 2.05 V, which is nearly equal to the superposition of the respective Voc values of the subcells. More importantly, the 2T TSC simultaneously shows outstanding operational and UV stabilities.