Chen Weijie

The study reports an europium (III) trifluoromethanesulfonate [Eu(OTF)₃] additive to enhance the performance and high-temperature photostability of PSCs. Eu(OTF)₃ suppresses the iodine vacancy defects in perovskite films, boosting the PCE to 23.8%. The Eu(OTF)₃-based PSCs retain 82% of their initial PCE after 1500 h under 85 ± 5 °C and 1 sun illumination in ambient air.

Abstract

Perovskite solar cells (PSCs) have witnessed a meteoric rise in device performance. However, maintaining photostability, particularly under thermal stress, remains a challenge due to defect formation in the perovskite layer. This study introduces europium (III) trifluoromethanesulfonate [Eu(OTF)₃] as a multifunctional additive in two-step processed perovskite films, significantly improving the performance and high-temperature photostability of n-i-p PSCs. Density function theory (DFT) calculations reveal that the OTF⁻ anion strongly coordinates with Pb²⁺, effectively inhibiting iodine vacancy defect formation. The addition of Eu(OTF)₃ promotes perovskite grain growth to ≈2 µm and enhances film crystallinity. PSCs with a structure of ITO/SnO₂/perovskite/PDCBT/NiOx/Au achieve a champion power conversion efficiency (PCE) of 23.8%. Under 85 ± 5 °C and 1 sun illumination at an open circuit in ambient air, the PSCs with Eu(OTF)₃ retain 82% of their initial PCE after aging for 1500 h.

This study reports the first prototype of filterless bandpass photodetectors based on thick 2D/3D perovskite heterojunctions. Due to the presence of strong excitonic absorption of the 2D perovskites employed, filterless bandpass detectors with record spectral rejection ratios (SRR ≅ 2000) and ultrasharp response edges (Δλ = 10 ± 1 nm) are developed. New design rules for filterless bandpass detectors are proposed in this work.

Abstract

Bandpass photodetectors have tremendous applications in colorimetric analysis, light communication, imaging and machine vision systems. Compared to broadband photodetectors combined with external optical filters, solution-processed filterless bandpass photodetectors enjoy high integration density and low cost, but suffer from broadened response edges and insufficient spectral rejection ratios (SRRs). Here, prototype filterless bandpass photodetectors with near square-shape photoresponse are developed based on (C _m H_{2 m+ 1}NH₃)₂PbI₄/MAPbI₃ (m = 4–8) and (C _m H_{2 m+ 1}NH₃)₂PbBr₄/MAPbBr₃ (m = 2–8) perovskite heterojunctions. The strong and sharp excitonic absorption of 2D perovskites defines the ultranarrow response onset widths of 10 ± 1 nm. Besides, the strong photoluminescence (PL) self-absorption of 2D perovskites suppresses the PL leakage from the front absorber to the back photoactive region, which is crucial to the achieved record high SRR of >2000. By integrating Br-based 2D/3D perovskite photodetectors with onset edge wavelength discrimination of ≈20 nm, a multiple-channel optical communication system with low spectral crosstalk is demonstrated.

By introducing MBene into the green antisolvent, the grain growth of perovskite films in an air environment is effectively improved, defects are passivated, the energy level structure is enhanced, and the power conversion efficiency reaches 24.22%, with stability also improved.

Abstract

High-performance perovskite solar cells (PSCs) fabricated in ambient air are considered inevitable for low-cost commercial manufacturing. However, passivating perovskite film defects and controlling the crystallization process are critical for achieving high performance in PSCs. This study proposes using the novel 2D material MBene in green antisolvent to simultaneously modulate the crystallization and passivation defects of perovskites. MBene facilitates the passivation of uncoordinated Pb²⁺ ions, thereby enhancing the formation energy of vacancies within the perovskite film and adjusting the energy level structure. Moreover, MBene increases nucleation sites for perovskite, significantly extending crystal growth and improving film crystallinity, thereby reducing non-radiative recombination. Consequently, champion devices treated with MBene achieve a power conversion efficiency (PCE) of 24.22% when fabricated in air, and exhibit superior humidity and long-term stability. Furthermore, PSCs with added MBene exhibit significant long-term stability under various environmental conditions, including humidity and heat. The study results lay a foundation for the development of MBene materials in photovoltaics, revealing their mechanism as a new type of 2D material in perovskites, and providing new insights for industrially producing efficient and stable solar cells.

A highly effective 3D fluoride molecular glue strategy has been developed for efficient and stable PSCs. Simultaneous incorporation of the KBF₄/TFMSA demonstrates 25.8 % PCE with negligible hysteresis, and 1 cm² PSCs presents a certified 24.57 % PCE. The KBF₄ and TFMSA afford 3D fluoride passivator by strong intramolecular hydrogen bonding. Synergistic passivation effect toward the SnO₂ and perovskite layer can reduce the non-radiative recombination and guarantee high-performance including exceptional stability.

Abstract

Aiming at numerous defects at SnO₂/perovskite interface and lattice mismatch in perovskite solar cells (PSCs), we design a kind of three-dimensional (3D) molecular glue (KBF₄-TFMSA), which is derived from strong intramolecular hydrogen bonding interaction between potassium tetrafluoroborate (KBF₄) and trifluoromethane-sulfonamide (TFMSA). A remarkable efficiency of 25.8 % with negligible hysteresis and a stabilized power output of 25.0 % have been achieved, in addition, 24.57 % certified efficiency of 1 cm² device is also obtained. Further investigation reveals that this KBF₄-TFMSA can interact with oxygen vacancies and under-coordinated Sn(IV) from the SnO₂, in the meantime, FA⁺ (NH₂−C=NH₂ ⁺) and K⁺ cations can be well fixed by hydrogen bonding interaction between FA⁺ and BF₄ ⁻, and electrostatic attraction between sulfonyl oxygen and K⁺ ions, respectively. Thereby, FAPbI₃ crystal grain sizes are increased, interfacial defects are significantly reduced while carrier extraction/ transportation is facilitated, leading to better cell performance and excellent stabilities. Non-encapsulated devices can maintain 91 % of their initial efficiency under maximum-power-point (MPP) tracking while continuous illumination (~100 mW cm⁻²) for 1000 h, and retain 91 % of the initial efficiency after 1000 h “double 60” damp-heat stability testing (60 °C and 60 %RH (RH, relatively humidity)).

An asymmetric 9H-thieno[2′,3′ : 4,5]thieno[3,2-b]indole (TTID) core based on the hybrid strategy is constructed. With the hybrid thieno[2,3-b]thiophene unit, the synthesized K1 and KF SAMs show favorable surface wettability, downshifted HOMO energy level, and good defect passivation capability. The fluorine substituent donates high dipole moment for the KF molecule and enhanced device stability. Solar cell with KF exhibits a certified PCE of 25.17 % and exceptional operational stability.

Abstract

Carbazole-based self-assembled molecules (SAMs) are widely applied in inverted perovskite solar cells (iPSCs) due to their unique molecular properties. However, the symmetrical structure of the carbazole-based SAMs makes it difficult to finely regulate their performance, which impedes the further enhancement of the efficiency and stability of iPSCs. This work demonstrates that by constructing an asymmetric carbazole core, 9H-thieno[2′,3′ : 4,5]thieno[3,2-b]indole) (TTID), the key properties of SAM molecules can be effectively regulated. It has been confirmed that the hybrid thieno[2,3-b]thiophene unit of this asymmetric core governs the energy level, the surface wettability, and the defect passivation capability of the SAMs, while the substituent of core has a greater impact on the molecular dipole and device stability. The synergistic effects from thieno[2,3-b]thiophene and fluorine lead to the KF-derived iPSC demonstrating a certified power conversion efficiency (PCE) of 25.17 % and excellent operational stability. This hybrid design concept offers a promising approach for the further structural modification of SAMs in iPSCs.

A novel solvent optimization approach is used to improve the efficiency and stability of inverted OSCs by utilizing the polar cosolvent DMF to prepare ZnO layers. The incorporation of polar cosolvent DMF not only facilitated the sustainable formation of the crucial intermediate Zn (OH)₂, but also contributed to reducing vacancy defects and eliminating amine residues in DMF-ZnO bulk films, thereby significantly decreasing the photocatalytic effect in corresponding devices.

Abstract

Here, a simple method of applying dimethylformamide (DMF) as cosolvent in the sol-gel technology is used to improve the quality of ZnO bulk films. First-principles calculations show that with the addition of polar solvent DMF, the adsorption energy (E_ads) between the solvent and Zn(OH)₂ increases from −1.42 to −1.74 eV, which can stabilize the existence of Zn(OH)₂, thereby promoting the ZnO synthesis. Besides, the elimination of amine residues in the DMF-ZnO film significantly suppress the photocatalytic activity induced by amine-induced coordination or redox reactions. Inverted organic solar cells (OSCs) based on PM6:Y6 and PM6:BTP-eC9 achieves impressive power conversion efficiencies (PCE) of 17.58 and 18.14%, respectively. Furthermore, benefiting from the reduced defects of bulk ZnO, pseudo-bilayer bulk heterojunction (PBHJ) devices based on the optimized ZnO film exhibited superior stability, the PM6:Y6 devices based on DMF-ZnO ETLs can maintain 90.28% of their initial PCE after 1000 h of thermal aging at 85 °C, and 80.98% of their initial PCE after 168 h of UV aging. This simple solvent optimization strategy can significantly improve the charge transport of ZnO bulk films, making it a reliable strategy for the preparation of electron transport layers in OSCs.

DL-serine hydrazide hydrochloride (DL-SH) containing reducing group is introduced into FA-Cs perovskite to promote nucleation and phase transition in antisolvent-free method. Hydrazine inhibits the production of volatile iodine, inhibits ion migration, and enhances the stability of the device. Finally, DL-SH added device achieves a champion efficiency of 22.22%, and maintains 85.88% of the initial efficiency after continuous exposure under 1 sun for 7000 s at a relative humidity of ≈40%.

Abstract

The efficiency and stability of solar cells are two key indicators that determine for the commercial feasibility of photovoltaic devices. Formamidine-cesium perovskite has been extensively investigated since its excellent thermal stability and has great potential in achieving high power conversion efficiency. However, during the aging process, especially under light conditions, formamidine-rich perovskites are prone to produce iodine, and the escape of iodine is one of the important factors leading to device degradation. Here, DL-Serine Hydrazide Hydrochloride containing the reducing group is introduced into the precursor solution of formamidine-cesium perovskite, which achieves multiple-site passivation. Hydrazine reacts with iodine to reduce it to iodine ions, inhibiting the escape of iodine. In addition, carbonyl groups and uncoordinated lead ions form coordination bonds to reduce defects. In the end, the perovskite solar cell with DL-Serine Hydrazide Hydrochloride added achieves a champion efficiency of 22.22%, and maintains 85.88% of the initial efficiency after continuous exposure under 1 sun for 7000 s at a relative humidity of ≈40%. Additionally, DL-Serine Hydrazide Hydrochloride added device shows good stability in air environments with relative humidity of 50%–60%. DL-Serine Hydrazide Hydrochloride improves the stability of formamidine-rich perovskite solar cells and provides a low-cost strategy for commercial development.

A dipole electric field (DEF) is deployed at the CsPbI₃/carbon interface by using 4-trifluoromethyl-Phenylammonium iodide (CF₃-PAI), in which the ─NH₃ group anchors on the perovskite surface and the ─CF₃ group connects with carbon electrode, to enhance hole selectivity and charge separation. Consequently, the CsPbI₃ C-PSCs achieve an excellent efficiency of 18.33% with a high V _OC of 1.144 V.

Abstract

Carbon-based CsPbI₃ perovskite solar cells without hole transporter (C-PSCs) have achieved intense attention due to its simple device structure and high chemical stability. However, the severe interface energy loss at the CsPbI₃/carbon interface, attributed to the lower hole selectivity for inefficient charge separation, greatly limits device performance. Hence, dipole electric field (DEF) is deployed at the above interface to address the above issue by using a pole molecule, 4-trifluoromethyl-Phenylammonium iodide (CF₃-PAI), in which the ─NH₃ group anchors on the perovskite surface and the ─CF₃ group extends away from it and connects with carbon electrode. The DEF is proven to align with the built-in electric field, that is pointing toward carbon electrode, which well enhances hole selectivity and charge separation at the interface. Besides, CF₃-PAI molecules also serve as defect passivator for reducing trap state density, which further suppresses defect-induced non-radiative recombination. Consequently, the CsPbI₃ C-PSCs achieve an excellent efficiency of 18.33% with a high V _OC of 1.144 V for inorganic C-PSCs without hole transporter.

Perovskite solar cells (PSCs) have emerged as a leading low-cost photovoltaic technology. However, processing challenges in air pose a significant hurdle. Herein, a novel air processing technique, incorporating antisolvent vapors into a controlled air-quenching process, is presented for planar carbon-electrode PSCs. This method mitigates moisture-induced instability, resulting in champion power conversion efficiencies exceeding 20% and robust stability under ambient conditions.

Perovskite solar cells (PSCs) have emerged as a leading low-cost photovoltaic technology, achieving power conversion efficiencies (PCEs) of up to 26.1%. However, their commercialization is hindered by stability issues and the need for controlled processing environments. Carbon-electrode-based PSCs (C-PSCs) offer enhanced stability and cost-effectiveness compared to traditional metal-electrode PSCs, i.e., Au and Ag. However, processing challenges persist, particularly in air conditions where moisture sensitivity poses a significant hurdle. Herein, a novel air processing technique is presented for planar C-PSCs that incorporates antisolvent vapors, such as chlorobenzene, into a controlled air-quenching process. This method effectively mitigates moisture-induced instability, resulting in champion PCEs exceeding 20% and robust stability under ambient conditions. The approach retains 80% of initial efficiency after 30 h of operation at maximum power point without encapsulation. This antisolvent-mediated air-quenching technique represents a significant advancement in the scalable production of C-PSCs, paving the way for future large-scale deployment.

Highly scalable nanosphere lithography-assisted chemical etching method is developed to create light-trapping nanostructures in InGaP/GaAs dual-junction solar cells. The enhanced broadband absorption in the nanostructured device is ascribed to a combination of Fabry–Perot and guided-wave resonances into which incident light is scattered by the Al₂O₃/Ag nanostructured rear mirror. This versatile technique facilitates enhanced performance in InGaP/GaAs dual-junction solar cells.

III–V-based multijunction solar cells have become the leading power generation technology for space applications due to their high power conversion efficiency and reliable performance in extraterrestrial environments. Thinning down the absorber layers of multijunction solar cells can considerably reduce the production cost and improve their radiation hardness. Recent advances in ultrathin GaAs single-junction solar cells suggest the development of light-trapping nanostructures to increase light absorption in optically thin layers within III–V-based multijunction solar cells. Herein, a novel and highly scalable nanosphere lithography-assisted chemical etching method to fabricate light-trapping nanostructures in InGaP/GaAs dual-junction solar cells is studied. Numerical models show that integrating the nanostructured Al₂O₃/Ag rear mirror significantly enhances the broadband absorption within the GaAs bottom cell. Results demonstrate that the light-trapping nanostructures effectively increase the short-circuit current density in GaAs bottom cells from 14.04 to 15.06 mA cm⁻². The simulated nanostructured InGaP/GaAs dual-junction structure shows improved current matching between the GaAs bottom cell and the InGaP top cell, resulting in 1.12x higher power conversion efficiency. These findings highlight the potential of light-trapping nanostructures to improve the performance of III-V-based multijunction photovoltaic systems, particularly for high-efficiency applications in space.

In this study, the challenges of integrating self-assembled monolayers (SAMs) into large-scale perovskite solar modules (PSMs) using slot-die coating are explored. Herein, a novel approach is presented combining a triphenylamine-based polymer with SAMs to mitigate the wetting issues for SAM interlayers for layer-by-layer slot-die coating of p–i–n PSMs. In this method, the morphology of the buried interfaces and the current–voltage performance in general are improved.

The strategy of incorporating self-assembled monolayers (SAMs) with anchoring groups is an effective and promising method for interface engineering in perovskite solar cells with metal oxide charge-transporting layers. However, coating SAM layers in upscaled perovskite solar modules (PSMs) using slot-die coating is challenging due to the low viscosity and wettability of the solutions. In this study, a triphenylamine-based polymer poly([{5-[4-(diphenylamino)phenyl]-2-thienyl}(4-fluorophenyl)methylene]malononitrile) (pTPA)–TDP, blended with SAM based on 5-[4-[4-(diphenylamino)phenyl]thiophene-2-carboxylic acid, is integrated to address these challenges. And, p–i–n-oriented PSMs on 50 × 50 mm² substrates (12 sub-cells) are fabricated with a NiO hole-transport layer and organic interlayers for surface modification. Wetting angle mapping shows that ununiform regions of the slot-die-coated SAM has extreme hydrophobicity, causing absorber thickness fluctuations and macro-defects at buried interfaces. The blended interlayer at the NiO/perovskite junction homogenizes surface wettability and mitigates lattice strain, enabling the effective use of SAM properties on large surfaces. This improved energy level alignment, enhancing the power conversion efficiency of the modules from 13.98% to 15.83% and stability (ISOS-L-2, T ₈₀ period) from 500 to 1630 h. In these results, the complex effects of using SAM in slot-die-coating technology for large-scale perovskite photovoltaics are highlighted.

A new method is reported to produce perovskite solar cells by 4-source by coevaporation and a modified hole transport layer (loaded hole transport layer). The best cells reach ≈21% efficiency and comparable performing ≈20% cells maintain their original efficiency after 1000 h of maximum power tracking at 25 °C.

Organo-lead-halide perovskites are promising materials for solar cell applications with efficiencies now exceeding 26% for single junction, and over 33% for silicon tandem devices. Evaporation has proven viable for industrial scale-up but presents challenges for perovskite materials. Perovskite precursor is introduced into self-assembling MeO-2PACz hole transport layers for application to 4 source perovskite coevaporation. This allows precursors that can be difficult to add via evaporation, like methylammonium chloride. These precursor molecules influence growth during evaporation, film behavior during annealing as measured by photoluminescence, and aid the conversion to perovskite as shown by X-Ray diffraction. Devices have improved power conversion efficiency and stability compared to a control sample within the same evaporation. The best cells reach ≈21% efficiency and comparable performing ≈20% cells maintain their original efficiency after 1000 h of maximum power tracking at 25 °C. This process provides significant process flexibility for perovskite evaporation and requires no additional steps.

A roll-to-roll slot-die coating process is used to fabricate wide-bandgap CsFAPbBr₃ perovskite solar cells under ambient conditions. The optimized ink formulation, incorporating 5% CsBr with a DMSO: butanol (9:1) solvent mixture, enhances film morphology and crystallinity, yielding an efficiency of 8.97%. This work supports the scalable and cost-effective production of perovskite solar cells.

The growing demand for sustainable energy solutions has made the development of scalable, efficient, and cost-effective perovskite solar cells (PSCs) increasingly important. Wide-bandgap perovskites (WB-PSCs) stand out due to their efficiency in low-light conditions and their use in tandem solar cells. WB-PSCs are currently behind conventional PSCs in upscaling, with limited success in printing wide bandgap PSCs. Developing upscaling methods is essential to fully realize their potential in the renewable energy sector. This research addresses the development of roll-to-roll (R2R) slot-die coating of Cs_0.05FA_0.95PbBr₃-based WB-PSCs by focusing on improving the film formation process and ink formulation. By adding optimal concentration of CsBr and performing in situ characterization, we obtained Cs_0.05FA_0.95PbBr₃ films with enhanced morphology and crystallinity in ambient conditions (50% RH), without inducing secondary phase formation. In addition, slot-die coating defects are eliminated through introducing DMSO: Butanol (9:1) solvent system. The R2R coated wide-bandgap PSCs reaches a power conversion efficiency (PCE) of up to 8.97% under 1-sun conditions and 18.3% PCE under indoor conditions. The corresponding R2R coated modules with a 5 × 5 cm² active area achieve a PCE of 5.8%, representing a crucial step towards the high-throughput, cost-effective production of perovskite solar modules.

An environmental-friendly (halogen-free) 1-benzothiophene (BBT) is employed as solid additive and combined it with solvent vapor annealing (SVA) post-treatment to optimize the morphology of active layer and improve performance of OSCs. Ultimately, an impressive efficiency of 19.53% is obtained in D18-Cl:N3 OSCs, which is one of the highest reported efficiencies for binary OSCs to date.

Abstract

Volatile solid additive is an effective and simple strategy for morphology control in organic solar cells (OSCs). The development of environmentally friendly new additives which can also be easily removed without high-temperature thermal annealing treatment is currently a trend, and the working mechanism needs to be further studied. Herein, a highly volatile and non-halogenated solid additive 1-benzothiophene (BBT) is reported to regulate molecular aggregation and stacking of active layer components. According to the film-forming kinetics process, a momentary intermediate phase is formed during spin-coating, which slows down the film-forming process and leads to more ordered molecular stacking in the solid film after introducing solid additive BBT. Subsequently, after solvent vapor annealing (SVA) further treatment, the resultant blend films exhibit a tighter and more ordered molecular stacking. Consequently, the synergistic effect of solid additive BBT and SVA treatment can effectively control morphology of active layer and improve carrier transport characteristics, thereby enhancing the performance of OSCs. Finally, in D18-Cl:N3 system, an impressive power conversion efficiency of 19.53% is achieved. The work demonstrates that the combination of highly volatile solid additives and SVA treatment is an effective morphology control strategy, guiding the development of efficient OSCs.

Weakly basic ammonium sulfide ((NH₄)₂S, AS) is employed to modify PEDOT:PSS/Pb-Sn perovskite interface. AS can react with both PbI₂ and PEDOT:PSS to regulate perovskite crystallization, optimize PEDOT:PSS performance, and promote interface carrier transport. Consequently, single-junction Pb–Sn and all-perovskite tandem solar cells obtained power conversion efficiencies of 24.23% and 27.48%, respectively.

Abstract

The commonly used hole transport layer (HTL) Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) still has some shortcomings that will limit the development of Pb–Sn perovskite solar cells (PSCs). In this work, multifunctional ammonium sulfide (AS) is attempted to modify PEDOT:PSS/perovskite interface. AS has multiple effects on different functional layers and the device as a whole: a) optimize the perovskite crystallization by the formation of PbS nucleation sites; b) neutralize the acidity of PEDOT:PSS by reaction with PSS; c) promote carrier transport at HTL/perovskite interface by tuning the energy level of PEDOT:PSS. As a result, a power conversion efficiency of 24.23% is obtained in the reverse scanning direction and 23.84% in the steady-state output power test for the single-junction Pb–Sn PSCs, and 27.48% for all-perovskite tandem solar cells. These results show that AS modification can be an effective way to boost the development of Pb–Sn PSCs.

The cathode interface materials (CIMs) are crucial for organic solar cells (OSCs). Herein, Excellent CIMs PDINN-Br and PDINN-2Br are reported, by bromination of PDINN. Both of them have strong work function (WF) tunability, self-doping properties, and excellent film-forming properties. In particular, PDINN-2Br has shown good performance in different active layer devices.

Abstract

The cathode interface materials (CIMs) are crucial for organic solar cells (OSCs). Herein, excellent CIMs PDINN-Br and PDINN-2Br are reported, by bromination of PDINN. Both of them have strong work function (WF) tunability, self-doping properties, and excellent film-forming properties. They show higher electron mobility (over 2 × 10⁻⁴ cm² V⁻¹ s⁻¹) and conductivity (≈5 × 10⁻⁵ S cm⁻¹) than PDINN. Grazing-incidence wide-angle X-ray scattering measurements (GIWAXS) illustrate that PDINN-2Br has more ordered arrangement than PDINN and PDINN-Br. PDINN, PDINN-Br, and PDINN-2Br in PM6:Y6-based OSCs lead to 15.96%, 16.71%, and 17.03% power conversion efficiency (PCE), respectively. The PDINN-2Br has well performance as well in the PM6:PYIT and D18:L8BO OSCs, PCEs of 18.14% and 18.98% are obtained, respectively, which are higher than PDINN (16.97% and 18.01%).

A crystalline 3D non-fullerene acceptor named SF-HR is cost-effectively synthesized and introduced into D18:Y6 binary system as the third component. The ternary OSCs exhibit more complementary absorptions, cascaded energy levels, preferred face-on packing, and finer domain size, thus achieving a significantly higher PCE of 18.85% than that of the host binary device (16.97%).

Abstract

The advantages of 3D materials as guest components of ternary organic solar cells (TOSCs) are being realized, showing great potential in improving device performance. However, the correlation between their distinctive 3D structure and device performance remains largely unexplored. Herein, a 3D acceptor named SF-HR is cost-effectively synthesized utilizing a twisted spirofluorene core. SF-HR shows an edge-on oriented packing but not the disordered aggregation as other 3D molecules. When introduced into D18:Y6 binary system, SF-HR can induce more predominant face-on packing and finer domain size in ternary blend, which facilitates exciton dissociation and multi-direction charge transport. Besides, SF-HR exhibits complementary absorption and cascaded energy levels with D18 and Y6, contributing to the improvement of short-circuit current density (J _sc) and open-circuit voltage (V _oc), respectively. Accordingly, the optimized ternary device achieves higher V _oc of 0.893 V, J _sc of 27.13 mA cm⁻², and fill factor (FF) of 77.8%, respectively, than that of the host binary device, yielding an excellent efficiency of 18.85%. This success demonstrates that the utilization of a crystalline 3D material as a guest component represents a promising strategy for achieving state-of-the-art OSCs, which is conducive to understanding the relationship between 3D guest structure and device performance from a new perspective.

The synergistic effect of H⁺ + I⁻ oxidation reduces the formation energy of α-FAPbI₃, reduces the dependence of FAPbI₃ crystallization on MA⁺, and inhibits the phase separation of MA-FA during crystallization. Finally, blade-coated PSCs utilizing FA_0.9MA_0.1PbI₃ as the absorber with a bandgap at 1.54 eV achieved an impressive champion efficiency of 23.67%.

Abstract

The role of MA in FAMA mixed perovskite remains far from being fully understood, due to the intricate chemical evolutions in the precursor solutions. Adjusting the content of MA in FAMA mixed perovskite arbitrarily remains a great challenge. This study elucidates a synergistic effect between H⁺ and I⁻ oxidation which helps to reduce the content of MA in FA-dominated perovskite. Briefly, excessive H⁺ boosts the balanced and rapid assembly of MA and FA components in FA-dominated perovskite and hampers unfavorable chemical evolution induced by nucleophilic reaction between MA and FA in the precursor solution, while I⁻ oxidation accelerates the in situ crystallization of perovskite. Leveraging this synergistic effect, centimeter-scaled FA_xMA_(1-x)PbI₃ single crystals with arbitrarily adjustable values of x are successfully fabricated. In addition, peroxyacetic acid is introduced as the additive, enabling the blade-coated FA_0.9MA_0.1PbI₃ perovskite solar cells (PSCs) to achieve an impressive efficiency of 23.7%. The efficiency achieved here is among the highest values for blade-coated PSCs with FA content exceeding 90% so far. The optimized solution developed in this study achieved exceptional stability, allowing it to be stored under air conditions for over 2 months without significant degradation in cell efficiency. This outcome satisfies the requirements for commercialization.

A halogenation engineering is proposed to develop solid additives (fluorinated D1-F and chlorinated D1-Cl) with isolated positive/negative charge distributions. Two solid additives show strong non-covalent interactions with both donor and acceptor components, especially D1-Cl, leading to an optimized morphology. Therefore, the D1-Cl treated binary organic solar cells achieve an efficiency of up to 19.39%.

Abstract

By selectively interacting with acceptor components, various typed solid additives achieve boosted power conversion efficiency (PCE) in organic solar cells (OSCs). However, due to the efficient active layer being composed of donor and acceptor materials, it is difficult to obtain the desired morphology by manipulating the acceptor component alone, limiting further improvement of PCEs. Herein, two solid additives with a same backbone of thiophene-benzene-thiophene (halogen-free D1-H) but different halogen substituents (fluorinated D1-F and chlorinated D1-Cl) are developed to probe the working mechanism of halogenated variation of solid additives in OSCs. Unlike D1-H with continuous charge distributions, D1-F and D1-Cl show isolated positive charge distribution in benzene-core and negative charge distribution in thiophene, offering stronger non-covalent interactions with both donor (PM6) and acceptor (L8-BO), especially D1-Cl. Consequently, D1-Cl-treated active layer obtains an optimized phase separation and improved molecular packing, boosting PCE to 18.59% and device stability of OSCs, with 17.62% for D1-H-treated counterparts. Moreover, using D18:L8-BO and D18:BTP-eC9 as active layers, D1-Cl-treated binary OSCs obtain impressive PCEs of 19.29% and 19.39%, respectively. This work indicates that halogenation engineering developed in solid additives can effectively regulate morphology for improving PCE and stability of OSCs, and elucidates the underlying mechanism.

Quantifying charge extraction losses in organic solar cells is crucial for understanding the origin of power losses and, consequently, for improving the performance. An analytical framework is presented that utilizes a readily available observable photoshunt and its correlation with light intensities for evaluating charge transport properties of a solar cell.

Abstract

The low charge carrier mobility of molecular materials is one of the key obstacles to achieving higher efficiencies in organic photovoltaics. Therefore, understanding and quantifying charge collection losses owing to low mobility is an important challenge in organic photovoltaics and other emerging photovoltaic technologies. Here, an approach is proposed to use the photoshunt and its dependence on light intensity as an easily accessible indicator of charge-collection losses. The physical meaning of the photoshunt is explored using drift-diffusion simulations and an analytical model. The results show that the recombination current visible as the photoshunt is decreasing with increasing charge carrier mobility. Furthermore, a framework is presented for evaluating the short-circuit current losses in experimental data using a photoshunt. The study reveals that the charge-collection efficiency at shortcircuit is strongly influenced by the charge carrier mobility and light intensity.

Surface reconstruction helps to further improve the efficiency of solar cells. In this study, a novel surface reconstruction method is presented that transforms the top surface of perovskite films into a bilayer heterojunction (BLH). This BLH structure enables an order of magnitude reduction in surface trap density, reaching 26.1% efficiency in inverted perovskite solar cells with superior long-term operational stability.

Abstract

The efficiency of perovskite photovoltaics remains distant from their theoretical limits, primarily due to high photovoltage losses. Here a strategy is reported to minimize voltage losses by reconstructing the perovskite surface into a bilayer heterojunction (BLH) structure. Unlike conventional low-dimensional capping layers, typically constrained to a few nanometers to prevent low fill factors, this methodology facilitates a more comprehensive reaction with surface defects, allowing a more substantial capping layer (≈50 nanometers) without compromising charge transport integrity. Time-resolved microwave conductivity analysis indicates a significant reduction in trap density at the top region of the perovskite film, showing an order of magnitude lower than that of the pristine sample. Incorporating this BLH in inverted cells results in a remarkably low photovoltage deficit of 325 mV, leading to a power conversion efficiency (PCE) of 26.1% (25.72% certified). The encapsulated device maintains 94% of its original efficiency after 1200 h of maximum power point tracking under one sun illumination at 65 °C.

This study showcased a high-performance hybrid hole transport layer based on Nb₂O₅ and 2PACz by using ethanol-soluble alkoxide precursors and a self-assembled monolayer, which enhanced interfacial contact and defect passivation, thus delivering high PCEs up to 20.12% in organic solar cells.

Abstract

In this study, a high-performance inorganic-organic hybrid hole transporting layer (HTL) was developed using ethanol-soluble alkoxide precursors and a self-assembled monolayer (SAM). Three metal oxides-vanadium oxide (VO_x), niobium oxide (Nb₂O₅), and tantalum oxide (Ta₂O₅)-were synthesized through successive low-temperature (100 °C) thermal annealing (TA) and UV-ozone (UVO) treatments of their respective precursors: vanadium oxytriethoxide (EtO−V), niobium ethoxide (EtO−Nb), and tantalum ethoxide (EtO−Ta). Among these, the Nb₂O₅ film exhibited excellent transmittance, a high work function, and good conductivity, along with a more compact and uniform structure featuring fewer interfacial defects, which facilitated efficient charge extraction and transport. Furthermore, the deposition of a SAM of (2-(9H-carbazol-9-yl)ethyl)phosphonic acid (2PACz) on top of Nb₂O₅ further passivated defects, enhancing interfacial contact with the photoactive layer. The resulting inorganic-organic hybrid HTL of Nb₂O₅/2PACz demonstrated excellent compatibility with various photoactive blends, achieving impressive power conversion efficiencies of 19.44 %, 19.18 %, and 20.12 % for the PM6:L8-BO, PM6:BTP-eC9, and D18:BTP-eC9 based organic solar cells, respectively. 20.12 % is the best performance for bulk heterojunction organic solar cells with binary components as the photoactive layer.

The flawed surface lattice configuration with numerous unsaturated dangling bonds at the surface of FA-based perovskites not only trap photoexcited charge carriers but also trigger photochemical degradation of the absorber layer. A novel surface lattice engineering is developed to achieve efficient and stable inverted perovskite solar cells by coupling surface unsaturated ions, regulating ion bonding lengths/angles, renovating surface lattice configuration.

Abstract

State-of-the-art inverted perovskite solar cells (PSCs) have exhibited considerable promise for commercialization due to their prospective stability. However, the intricate crystallization of halide perovskite, especially for multi-component perovskites, not only distorts the surface lattice from its ideal form but also introduces numerous unsaturated dangling bonds to form surface defects, which can easily lead to reduced stability and poor performance. Herein, a surface lattice engineering is developed by coupling surface unsaturated ions and regulating ion bonding lengths/angles to achieve efficient and stable inverted PSCs. The renovated surface lattice not only eliminates shallow/deep level defects on the surface of perovskite, but also enhances photo/thermal stability of the materials. Moreover, the surface lattice engineering contributes to uniform potential surface, and improves energy-level alignment at the interfaces of the perovskite and C₆₀ carrier transport layer, enhancing charge carrier extraction and transportation. Finally, the champion PSC delivers an impressive efficiency of 25.82% (certified 25.5%). Moreover, these PSCs exhibit excellent operational stability, retaining 94% initial efficiency after more than ≈1 000h maximum power point test.

In hybrid perovskite/organic solar cells (HSCs), the interface between the perovskite and organic bulk-heterojunction (BHJ) is carefully engineered with dipole interfacial layers (DILs). These DILs form strong interfacial dipoles, effectively reducing energy barriers and suppressing hole accumulation. Additionally, DILs enhance near-infrared photon harvesting and charge transport, boosting efficiency to 24.0% and achieving stability of 1200 h under extreme moisture conditions.

Abstract

The potential of hybrid perovskite/organic solar cells (HSCs) is increasingly recognized owing to their advantageous characteristics, including straightforward fabrication, broad-spectrum photon absorption, and minimal open-circuit voltage (V _OC) loss. Nonetheless, a key bottleneck for efficiency improvement is the energy level mismatch at the perovskite/bulk-heterojunction (BHJ) interface, leading to charge accumulation. In this study, it is demonstrated that introducing a uniform sub-nanometer dipole layer formed of B3PyMPM onto the perovskite surface effectively reduces the 0.24 eV energy band offset between the perovskite and the donor of BHJ. This strategic modification suppresses the charge recombination loss, resulting in a noticeable 30 mV increase in the V _OC and a balanced carrier transport, accompanied by a 5.0% increase in the fill factor. Consequently, HSCs that achieve power conversion efficiency of 24.0% is developed, a new record for Pb-based HSCs with a remarkable increase in the short-circuit current of 4.9 mA cm⁻², attributed to enhanced near-infrared photon harvesting.

Nature Photonics, Published online: 02 October 2024; doi:10.1038/s41566-024-01542-8