Chen Weijie

The effect of measurement conditions on the current–voltage characteristics is evaluated in detail. It is shown that varying the measurement conditions can lead to significant differences in measured efficiency, which do not occur in the same manner on the module level. This entails considerable variations in cell-to-module power factors. Hints to increase the significance of solar cell measurements are given.

Precise solar cell measurements become more and more challenging due to the increasing complexity of metallization patterns and the sensitivity to rear side illumination for bifacial cell concepts. In this context, the measurement conditions under which conversion efficiencies are determined need to be closely examined: Different efficiency values can occur for the same solar cell because of different measurement conditions. To provide more transparency, a notation has recently been published, which unambiguously characterizes the measurement conditions used and which is included in the calibration documents of the calibration laboratories ISFH CalTeC and Fraunhofer ISE CalLab PV Cells. As this notation is held rather technical and no quantitative assessment is given so far, herein, the effects associated with different measurement conditions are analyzed and quantified in detail for typical industrial-type solar cells. It is shown that varying the measurement conditions as well as the busbar concept can lead to significant differences in measured efficiency of 0.5%_abs. The power gains coming from different cell measurement configurations do not occur in the same manner on the module level though and can lead to considerable variations in cell-to-module power factors. Several hints to increase the significance of solar cell measurements are given.

A method for high-throughput preparation of chemical bath deposited SnO₂ has been developed through incorporating a concentrated tin source stabilized by the ethanol ligand, and doping with antimony. Consequently, the deposition time of SnO₂ can be appreciably reduced from 3–4 h to only 5 min while maintaining 95% of the maximum efficiency when assembled in perovskite solar cells.

Abstract

Chemical bath deposited (CBD) SnO₂ is one of the most prevailing electron transport layers for realizing high-efficiency perovskite solar cells (PSCs) so far. However, the state-of-the-art CBD SnO₂ process is time-consuming, contradictory to its prospect in industrialization. Herein, a simplified yet efficient method is developed for the fast deposition of SnO₂ electrodes by incorporating a concentrated Sn source stabilized by the ethanol ligand with antimony (Sb) doping. The higher concentration of Sn source promotes the deposition rate, and Sb doping improves the hole-blocking capability of the CBD SnO₂ layer so that its target thickness can be reduced to further save the deposition time. As a result, the deposition time can be appreciably reduced from 3–4 h to only 5 min while maintaining 95% of the maximum efficiency, indicating the power of the method toward high-throughput production of efficient PSCs. Additionally, the CBD SnO₂ substrates are recyclable after removing the upper layers of complete PSCs, and the refurbished PSCs can maintain ≈98% of their initial efficiency after three recycling-and-fabrication processes.

Nature Communications, Published online: 04 December 2023; doi:10.1038/s41467-023-43852-5

Nature Energy, Published online: 04 December 2023; doi:10.1038/s41560-023-01392-8

Publication date: February 2024

Source: Nano Energy, Volume 120

Author(s): Chong Dong, Dayu Liu, Afei Zhang, Xuke Yang, Haisheng Song, Long Hu, Xiong Li, Ling Xu, Liang Wang, Chao Chen, Jiang Tang

Publication date: 17 January 2024

Source: Joule, Volume 8, Issue 1

Author(s): Jin-Woo Lee, Heung-Goo Lee, Eun Sung Oh, Sun-Woo Lee, Tan Ngoc-Lan Phan, Sheng Li, Taek-Soo Kim, Bumjoon J. Kim

The intermolecular forces in DMA²⁺ establish a precise distance between the colloidal particles in perovskite precursor, resulting in pure 2D perovskite with n = 3, effectively enhancing carrier transport of the 3D perovskites. Finally, the devices accomplish a power conversion efficiency of 25.26% (certified 25.04%) and 23.56% at a larger area (1 cm²).

Abstract

In two-dimensional/three-dimensional (2D/3D) perovskite heterostructure, randomly distributed multiple quantum wells (QW) 2D perovskites are frequently generated, which are detrimental to carrier transport and structural stability. Here, the high quality 2D/3D perovskite heterostructure is constructed by fabricating functional-group-induced single QW Dion–Jacobson (DJ) 2D perovskites. The utilization of ─OCH₃ in the precursor solution facilitates the formation of colloidal particles with uniform size, resulting in the production of a pure 2D DJ perovskite with an n value of 3. This strategy facilitates the improvement of 3D structural stability and expedites carrier transport. The resultant devices accomplish a power conversion efficiency of 25.26% (certified 25.04%) and 23.56% at a larger area (1 cm²) with negligible hysteresis. The devices maintain >96% and >89% of their initial efficiency after continuous maximum power point tracking under simulated AM1.5 illumination for 1300 h and under damp-heat conditions (85 °C and 85% RH) for 1010 h, respectively.

In spectrometric characterization, current–voltage curves of multi-junction solar cells are measured under different defined spectral conditions allowing for accurate determination of the current matching point. Herein, this method is extended from dual-junction to triple-junction solar cells. First, the method is presented. Afterward, the application and evaluation are exemplarily shown for a III–V on silicon triple-junction solar cell.

Spectrometric characterization allows for accurate determination of the current matching point and investigation of sub-cell properties of multi-junction solar cells. It is widely used for dual-junction solar cells. Although the concept is suggested for triple-junction solar cells, it is only applied for the variation of two sub-cells. In this work, the applicability and evaluation procedure for a systematic variation of all three sub-cells of a triple-junction solar cell are presented. Clearly defined measurement conditions are derived which allow for meaningful characterization and comparisons of different triple-junction devices. The presented procedure is exemplarily tested on a III–V on silicon triple-junction solar cell using an light-emitting diode-based solar simulator where all needed spectral conditions can be calculated in advance and accordingly adjusted. Spectral conditions around the air mass 1.5 global spectrum are chosen and a fit routine to determine the current matching point from the discrete measurement points is proposed and validated by a measurement with a higher resolution around the current matching point. Finally, it is shown that the spectral conditions applied during the measurement also reflect outdoor conditions. This highlights the relevance of the presented procedure beyond the determination of the current-matching conditions.

A nonfused ring electron acceptor based on benzotriazole moiety with asymmetric terminal groups is first synthesized to reveal the effect of asymmetric terminal groups on optoelectronic property, molecular packing behaviors, charge transports, film morphology, as well as photovoltaic performance.

Nonfused ring electron acceptors (NFREAs) have received much attention due to their distinguished advantages such as simple chemical structure, facile synthesis, and low cost. Herein, three NFREAs with asymmetric and symmetric terminal groups, named CY101, CY102, and CY103, respectively, are designed and synthesized. The effect of terminal groups on the photophysical, electrochemical, and charge transport properties of the NFREAs is further investigated, providing insight to the relationships between the molecular structures and properties of NFREAs. It is found that the asymmetric NFREA CY102-based organic solar cells (OSCs) can yield a power conversion efficiency of 11.30%, which is higher than those of the symmetric CY101-based OSCs (10.20%) and CY103-based OSCs (8.99%). These results indicate that the asymmetric design strategy can be introduced into NFREAs to engage the high-performance OSCs.

A facile CsF treatment enhances CZTSSe grain growth and phase homogeneity, resulting in effective charge transport and a favorable P-N junction. This leads to a significant performance enhancement in CZTSSe thin-film solar cells, increasing efficiency from 8.38% to 10.20%. The CsF-treated CZTSSe bottom cell is integrated into a mechanically-stacked perovskite/CZTSSe 4-terminal tandem solar cell, achieving the highest reported tandem efficiency of 23.01%.

Abstract

Cu₂ZnSn(S,Se)₄ (CZTSSe) thin film solar cells are an attractive choice for a bottom cell of the low-cost and environmental tandem solar cells with perovskite. However, the progress in developing efficient perovskite/CZTSSe tandem solar cells has been hindered by the lack of high performance of the CZTSSe bottom cell. Here, an efficient CZTSSe bottom cell is demonstrated by adopting a facile and effective CsF treatment process. It is found that the CsF treatment not only facilitates grain growth and improves phase homogeneity by suppressing the detrimental deep-level defects and secondary phases, but also induces larger band bending and stronger drift force at the P-N junction. As a result, the carrier extraction/transport can be effectively accelerated, while reducing the interfacial recombination. These combined effects eventually result in a significant performance enhancement from 8.38% to 10.20%. The CsF-treated CZTSSe solar cell is finally applied to the mechanically-stacked perovskite/CZTSSe 4-terminal tandem cell by coupling a semi-transparent perovskite top cell, which exhibits the highest reported tandem efficiency of 23.01%.

It reveals the degradation pathways of a wide range of state-of-the-art nonfullerene acceptors from molecular to aggregation level. The structural confinement and molecular ordering are responsible for molecular conformational stability under illumination. The origin of increased nonradiative decay under illumination is predominantly in the aggregated states with strong intermolecular interactions while the intramolecular exciton dynamics are stable.

Abstract

Wide-bandgap (WBG) perovskite solar cells (PSCs) have drawn great attention owing to their promising potential for constructing efficient tandem solar cells. However, the rapid crystallization results in poor film properties and easy formation of defects, thereby greatly restricting the acquisition of a small open-circuit voltage (V _OC) deficit due to the severe nonradiative recombination. Herein, it introduced the triethanolamine borate (TB) to effectively slow down the rapid crystallization for preparing highly crystalline and uniform WBG perovskite films with reduced defects. The strong intermolecular interaction (e.g., coordination and hydrogen bond) between TB and perovskite can suppress the halide vacancy formation and inhibit phase segregation for improving long-term stability. The devices based on a 1.65 eV perovskite absorber achieved a high efficiency of 21.55% with a V _OC of 1.24 V, demonstrating the V _OC deficit is as low as 0.41 V, which is one of the lowest reports. By combining a semitransparent WBG subcell with a narrow-bandgap tin-based PSC, the four-terminal tandem solar cell delivers a high efficiency of 26.48%.

Lead chloride (PbCl₂) is introduced into the co-evaporated (Cs, FA)Pb(I, Br)₃, which has significantly enhanced the structural stability of perovskite and accelerated interfacial charge transfer and carrier diffusion by inducing minor octahedral tilting and improving the crystallinity. Consequently, fully evaporated perovskite/silicon tandem solar cells have achieved a power conversion efficiency of 27.43% with an open-circuit voltage of 1.810 V.

Abstract

Thermal evaporation can significantly facilitate scalable, uniform, and conformal perovskite film, particularly well-suited for the preparation of perovskite/silicon (Si) tandem solar cells . However, the perovskite material easily induces a phase transition from a photoactive phase to a photoinactive phase, limiting the development of the stability and efficiency of tandem cells. Introducing lead chloride (PbCl₂) into wide-bandgap perovskite materials is beneficial for the fabrication of efficient and stable light-absorbing materials, but the microscopic mechanism of the effect of PbCl₂ on perovskite is still unclear. The study here reports evidences that the addition of PbCl₂ to improve perovskite film stability and optoelectronic performance is due to the minor octahedral tilting of the perovskite structure are reported. It also demonstrates that this strategy accelerates interfacial charge transfer and carrier diffusion in the perovskite bulk and heterojunction interfaces. Therefore, the wide-bandgap perovskite solar cells (PSCs) prepared by adding PbCl₂ exhibit a champion power conversion efficiency (PCE) of 17.80%. The PSCs retain 97% of their performance following 200 h of operation at the maximum power point under full 1-sun illumination. Finally, monolithic perovskite/Si tandem cells with record PCEs of 27.43% and an open-circuit voltage of 1.817 V are fabricated.

Ionic radius-controlled doping of NiO _x nanoparticles-based HTLs is achieved, resulting in tunable work functions (WFs) and enhanced conductivity. These HTLs are further modified with catechol for use in OSCs, achieving remarkable power conversion efficiencies (PCEs) of 18.42% (PM6:L8-BO) and 19.18% (D18:N3:F-BTA3) and setting new records for solution-processed inorganic nanoparticle HTL-based OSCs.

Abstract

Nickel oxide (NiO _x ) has garnered considerable attention as a prospective hole-transporting layer (HTL) in organic solar cells (OSCs), offering a potential solution to the stability challenges posed by traditional HTL, PEDOT:PSS, arising from acidity and hygroscopicity. Nevertheless, the lower work function (WF) of NiO _x relative to donor polymers reduces charge injection efficiency in OSCs. Herein, NiO _x nanoparticles are tailored through rare earth doping to optimize WF and the impact of ionic radius on their electronic properties is explored. Lanthanum (La³⁺) and yttrium (Y³⁺) ions, with larger ionic radii, are effectively doped at 1 and 3%, respectively, while scandium (Sc³⁺), with a smaller ion radius, allows enhanced 5% doping. Higher doping ratios significantly enhance WF of NiO _x . A 5% Sc³⁺ doping raises WF to 4.99 eV from 4.77 eV for neat NiO _x while maintaining high conductivity. Consequently, using 5% Sc-doped NiO _x as HTL improves the power conversion efficiency (PCE) of OSCs to 17.13%, surpassing the 15.64% with the neat NiO _x . Further enhancement to 18.42% is achieved by introducing the reductant catechol, outperforming the PEDOT:PSS-based devices. Additionally, when employed in a ternary blend system (D18:N3:F-BTA3), an impressive PCE of 19.18 % is realized, top-performing among reported OSCs utilizing solution-processed inorganic nanoparticles.

A poly(3-hexylthiophene)/perovskite (P3HT/PVK) heterointerface is created by using a novel strategy of spinodal decomposition, which effectively alleviates both energy and carrier losses in perovskite solar cells (PSCs). This innovative approach achieves a remarkable 24.53% power conversion efficiency for PSCs.

Abstract

The best research-cell efficiency of perovskite solar cells (PSCs) is comparable with that of mature silicon solar cells (SSCs); However, the industrial development of PSCs lags far behind SSCs. PSC is a multiphase and multicomponent system, whose consequent interfacial energy loss and carrier loss seriously affect the performance and stability of devices. Here, by using spinodal decomposition, a spontaneous solid phase segregation process, in situ introduces a poly(3-hexylthiophene)/perovskite (P3HT/PVK) heterointerface with interpenetrating structure in PSCs. The P3HT/PVK heterointerface tunes the energy alignment, thereby reducing the energy loss at the interface; The P3HT/PVK interpenetrating structure bridges a transport channel, thus decreasing the carrier loss at the interface. The simultaneous mitigation of energy and carrier losses by P3HT/PVK heterointerface enables n-i-p geometry device a power conversion efficiency of 24.53% (certified 23.94%) and excellent stability. These findings demonstrate an ingenious strategy to optimize the performance of PSCs by heterointerface via Spinodal decomposition.

A V³⁺/V²⁺ redox couple was developed to accelerate the spontaneous redox reactions between Sn⁴⁺ and Pb⁰, enabling the perpetual regeneration of Sn²⁺ and Pb²⁺ for self-healing tin-lead mixed perovskites under light soaking. The target vanadium-containing tin-lead mixed perovskite (V−Sn−Pb) solar cells showed substantially improved durability over 1000 hours under operation.

Abstract

The facile oxidation of Sn²⁺ to Sn⁴⁺ poses an inherent challenge that limits the efficiency and stability of tin-lead mixed (Sn−Pb) perovskite solar cells (PSCs) and all-perovskite tandem devices. In this work, we discover the sustainable redox reactions enabling self-healing Sn−Pb perovskites, where their intractable oxidation degradation can be recovered to their original state under light soaking. Quantitative and operando spectroscopies are used to investigate the redox chemistry, revealing that metallic Pb⁰ from the photolysis of perovskite reacts with Sn⁴⁺ to regenerate Pb²⁺ and Sn²⁺ spontaneously. Given the sluggish redox reaction kinetics, V³⁺/V²⁺ ionic pair is designed as an effective redox shuttle to accelerate the recovery of Sn−Pb perovskites from oxidation. The target Sn−Pb PSCs enabled by V³⁺/V²⁺ ionic pair deliver an improved power conversion efficiency (PCE) of 21.22 % and excellent device lifespan, retaining nearly 90 % of its initial PCE after maximum power point tracking under light for 1,000 hours.

Nature Energy, Published online: 30 November 2023; doi:10.1038/s41560-023-01378-6

In this review, the buried interlayer design shall regulate energy level structure of inorganic NiO _x hole-transport layer and passivate interfacial defects at NiO _x /perovskite interface, which can be implemented by energy level alignment engineering and interfacial defect passivation engineering for improving the photovoltaics performance and long-term operational stability of perovskite solar cells.

The power conversion efficiency of inverted perovskite solar cells (PSCs) based on p–i–n structure exceeds 25%, largely owning to the persistent improvement on the quality of heterojunction interface. Nickel oxide (NiO _x ) of low cost and superior chemical stability is one of the most promising candidates as hole-transport material that is suitable for large-scale fabrication. Meanwhile, the certified efficiency of inorganic NiO _x -based inverted PSCs surpasses 25% via improving the poor quality of buried interface contact, which is originated from large offset of valence band energy level, as well as high density of interfacial defects between NiO _x hole-transport layer and perovskite film. In this review, the development and progress in buried interface engineering of inorganic NiO _x layer are systematically summarized, including strategies on energy level alignment and interfacial defect passivation, which are adopted to promote the better energy level alignment and suppress the defect-assisted nonradiative recombination at interface. On the basis of deeper understanding of buried interface features, some novel materials and methods for interface modification can be rationally designed. Perspectives on future development of efficient and stable large-scale perovskite solar modules and tandem cells are also provided.

N,N-diphenylguanidine monohydrobromide (DPGABr) dissolved in acetonitrile is blade-coated on the perovskite layer in air to reconstruct the perovskite surface by forming amorphous DPGABr–PbI₂ complex in hundreds of milliseconds. The resultant devices show a relative enhancement of 15% in the average power conversion efficiency (PCE). More importantly, the device performance undergoes negligible degradation even after 1-year storage in air.

Abstract

Blade coating has been developed to be an essential technique for large-area fabrication of perovskite solar cells (PSCs). However, effective surface treatment of the perovskite layer, which is a critical step for improving PSC performance, remains challenges during blade coating due to the short interaction time between the modification solution and the perovskite layer, as well as the limited selection of available organic solvents. In this study, a novel modifier N,N-diphenylguanidine monohydrobromide (DPGABr) dissolved in acetonitrile (ACN) is blade coated on the MA_0.7FA_0.3PbI₃ surface in air to reconstruct the perovskite surface in hundreds of milliseconds. This work finds that the solvent ACN rapidly dissolves organic iodide of the perovskite layer and leads to a PbI₂-rich surface, providing reactive sites for DPGABr to form a thin DPGABr/PbI₂ complex layer. This surface reconstruction can effectively passivate defects and induce n-type doping on the perovskite surface to facilitate electron transfer. The resultant devices show a 15% improvement in average power conversion efficiency. More importantly, the devices with the surface reconstruction show outstanding long-term stability, with negligible performance degradation even after 1-year storage in air. This study presents a convenient and effective approach for improving the performance of blade-coated PSCs prepared in air.

This work introduces a novel and effective strategy to increase the bandgap of solution-based two-step processed perovskite solar cells beyond 1.65 eV. The strategy – incorporating bromide in both deposition steps – improves the photophysical and material properties of the perovskite film. This allows a straightforward implementation in monolithic perovskite/silicon tandem solar cells with efficiencies of up to 23.7%.

Abstract

For high-performance application of perovskite solar cells (PSCs) in monolithic perovskite/silicon tandem configuration, an optimal bandgap and process method of the perovskite top cell is required. While the two-step method leads to regular perovskite film crystallization, engineering wider bandgaps (E _g > 1.65 eV) for the solution-based two-step method remains a challenge. This work introduces an effective and facile strategy to increase the bandgap of two-step solution-processed perovskite films by incorporating bromide in both deposition steps, the inorganic precursor deposition (step 1, PbBr₂) and the organic precursor deposition (step 2, FABr). This strategy yields improved charge carrier extraction and quasi-Fermi level splitting with power conversion efficiencies (PCEs) of up to 15.9%. Further improvements are achieved by introducing CsI in the bulk and utilizing LiF as surface passivation, resulting in a stable power output exceeding 18.5% for E _g = 1.68 eV. This additional performance boost arises from enhanced perovskite film crystallization, leading to improved charge carrier extraction. Laboratory scale monolithic perovskite/silicon solar cells (TSCs) (1 cm² active area) achieve PCEs up to 23.7%. This work marks a significant advancement for wide bandgap two-step solution-processed perovskite films, enabling their effective use in high-performance and reproducible PSCs and perovskite/silicon TSCs.