Chen Weijie

A surface state manipulation is developed to effectively address the issue of poor interface contacts in the inverted perovskite solar cells (PSCs). The strong chemical interaction between highly electronegative 4-fluorophenethylamine hydrochloride (p-F-PEACl) and perovskite film reduces non-radiative recombination and facilitates efficient charge extraction of interface. Finally, an overall efficiency improvement from 22.34% to 24.78% is achieved.

Abstract

Inverted perovskite solar cells (PSCs) are considered as the most promising avenue for the commercialization of PSCs due to their potential inherent stability. However, suboptimal interface contacts between electron transport layer (ETL) (such as C₆₀) and the perovskite absorbing layer within inverted PSCs always result in reduced efficiency and poor stability. Herein, a surface state manipulation strategy has been developed by employing a highly electronegative 4-fluorophenethylamine hydrochloride (p-F-PEACl) to effectively address the issue of poor interface contacts in the inverted PSCs. The p-F-PEACl demonstrates a robust interaction with perovskite film through bonding of amino group and Cl⁻ with I⁻ and Pb²⁺ ions in the perovskite, respectively. As such, the surface defects of perovskite film can be significantly reduced, leading to suppressed non-radiative recombination. Moreover, p-F-PEACl also plays a dual role in enhancing the surface potential and improving energy-level alignment at the interfaces between the perovskite and C₆₀ carrier transport layer, which directly contributes to efficient charge extraction. Finally, the open-circuit voltage (V _oc) of devices increases from 1.104 V to 1.157 V, leading to an overall efficiency improvement from 22.34% to 24.78%. Furthermore, the p-F-PEACl-treated PSCs also display excellent stability.

We provided a new method for accurately controlling the nucleation kinetics of tin halide perovskite films through modulating zeta potential of tin halide perovskite colloids. A fast nucleation rate was achieved by adding 3-aminopyrrolidine dihydroiodate (APDI₂) in the precursor solution to change the zeta potential of the FASnI₃ colloids. The high-quality tin halide perovskite film with APDI₂ yields a high photovoltaic efficiency of 15.13 %.

Abstract

Tin halide perovskites (THPs) have demonstrated exceptional potential for various applications owing to their low toxicity and excellent optoelectronic properties. However, the crystallization kinetics of THPs are less controllable than its lead counterpart because of the higher Lewis acidity of Sn²⁺, leading to THP films with poor morphology and rampant defects. Here, a colloidal zeta potential modulation approach is developed to improve the crystallization kinetics of THP films inspired by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. After adding 3-aminopyrrolidine dihydro iodate (APDI₂) in the precursor solution to change the zeta potential of the pristine colloids, the total interaction potential energy between colloidal particles with APDI₂ could be controllably reduced, resulting in a higher coagulation probability and a lower critical nuclei concentration. In situ laser light scattering measurements confirmed the increased nucleation rate of the THP colloids with APDI₂. The resulting film with APDI₂ shows a pinhole-free morphology with fewer defects, achieving an impressive efficiency of 15.13 %.

Publication date: June 2024

Source: Journal of Energy Chemistry, Volume 93

Author(s): Xingrui Zhang, Jian Zhang, Wei Wang, Boyuan Hu, Yayu Dong, Debin Xia, Kaifeng Lin, Yulin Yang

Herein, a ferrocene capping layer is introduced on the surface of Sn–Pb perovskite to maintain a reducing environment. This approach significantly improves the power conversion efficiency (PCE) from 17.49% to 21.02% and maintains 87% of its initial PCE after light exposure at 1 sun conditions in an N₂ atmosphere for 288 h.

The Sn–Pb mixed perovskite with a narrow bandgap is essential for the construction of all-perovskite tandem solar cells. However, the oxidation of Sn²⁺ to Sn⁴⁺ makes the fabrication of Sn–Pb perovskite solar cells (PSCs) challenging. Herein, a ferrocene (Fc) capping layer is introduced on the surface of Sn–Pb mixed perovskite to maintain a reducing environment. This is due to a strong electron supply capacity from the π-orbitals in cyclopentadiene in Fc, which effectively suppresses the oxidation of Sn²⁺, reduces the defect density, and leads to an improvement in carrier lifetime. Therefore, the Fc capping layer significantly improves the power conversion efficiency (PCE) of single-junction Sn–Pb PSCs from 17.49% to 21.02%. It maintains 87% of its initial PCE after light exposure at 1 sun condition in N₂ atmosphere for 288 h, demonstrating good long-term stability. The strategy outlined herein offers a straightforward and efficient approach to enhance the stability and PCE of narrow-bandgap Sn–Pb mixed PSCs.

The composite modification ideas of phase-change materials (PCMs) suitable for photovoltaic (PV) or PV/T integration are summarized. The research status of PCM-integrated PV and PV/T is introduced. The feasibility and economy of PV–PCM systems and PV/T-PCM systems are evaluated. The future research emphases of PCMs in PV and PV/T integration are prospected.

Photovoltaic (PV) cells convert solar energy into electricity is currently the cleanest and most economical way to generate electricity. Nevertheless, just a portion of the solar power can be transformed into electrical energy, while the remaining portion is converted into heat, leading to an increase in the temperature of the PV cells. The rise in temperature will not only cause a decrease in the electrical efficiency of PV cells, but it may also impact their life span. By placing phase-change materials (PCMs) on the back of the PV cells, it is possible to decrease the temperature increase and enhance the electrical efficiency. The heat collected by PCMs can also be taken away using liquid cooling and put to use. In this article, the classification, performance evaluation, and composite modification technology of PCMs are introduced in detail. The practical application requirements of PCMs in thermal management of PV cells are discussed, and some new ideas of applying PCMs to PV cells are prospected. Moreover, the prior investigations regarding the incorporation of PCMs with PV systems and PV/T systems are also compiled, encompassing the various research perspectives and methodologies employed. In addition, the possible development direction in the future is prospected.

Using a simple synthesis process to convert waste Sn–Pb solder into SnI₂/PbI₂ and apply them to perovskite solar cells (PSCs). Meanwhile, Sn–Pb waste solder can be used as a reducing agent to remove Sn⁴⁺ from the Sn–Pb mixed perovskite precursor. The target Sn–Pb mixed PSC achieved an efficiency of 21.04%.

Abstract

The preparation of perovskite components (PbI₂ and SnI₂) using waste materials is of great significance for the commercialization of perovskite solar cells (PSCs). However, this goal is difficult to achieve due to the purity of the recovered products and the easy oxidation of Sn²⁺. Here, a simple one-step synthetic process to convert waste Sn–Pb solder into SnI₂/PbI₂ and then applied as-prepared SnI₂/PbI₂ to PSCs for high additional value is adopted. During fabrication, Sn–Pb waste solder is also employed to serve as a reducing agent to reduce the Sn⁴⁺ in Sn–Pb mixed narrow perovskite precursor and hence remove the deep trap states in perovskite. The target PSCs achieved an efficiency of 21.04%, which is better than the efficiency of the device with commercial SnI₂/PbI₂ (20.10%). Meanwhile, the target PSC maintained an initial efficiency of 80% even after 800 h under continuous illumination, which is significantly better than commercial devices. In addition, the method achieved a recovery rate of 90.12% for Sn–Pb waste solder, with a lab-grade purity (over 99.8%) for SnI₂/PbI₂, and the cost of perovskite active layer reduced to 39.81% through this recycling strategy through calculation.

Developing dopant-free hole transport layer (HTL) materials processed with green solvents is essential for producing high-performance perovskite solar cells. In this review, the intrinsic relationships between molecular structure, solubility, molecular stacking, and device performance are specifically discussed. It also proposes a molecular design guideline based on the Hansen solubility parameter principle to guide the green solvent-processable dopant-free organic HTL materials.

Abstract

Dopant-free hole transport layers (HTLs) are crucial in enhancing perovskite solar cells (pero-SCs). Nevertheless, conventional processing of these HTL materials involves using toxic solvents, which gives rise to substantial environmental concerns and renders them unsuitable for large-scale industrial production. Consequently, there is a pressing need to develop dopant-free HTL materials processed using green solvents to facilitate the production of high-performance pero-SCs. Recently, several strategies have been developed to simultaneously improve the solubility of these materials and regulate molecular stacking for high hole mobility. In this review, a comprehensive overview of the methodologies utilized in developing dopant-free HTL materials processed from green solvents is provided. First, the study provides a brief overview of fundamental information about green solvents and Hansen solubility parameters, which can serve as a guideline for the molecular design of optimal HTL materials. Second, the intrinsic relationships between molecular structure, solubility in green solvents, molecular stacking, and device performance are discussed. Finally, conclusions and perspectives are presented along with the rational design of highly efficient, stable, and green solvent-processable dopant-free HTL materials.

A wide-bandgap organic semiconductor PCz as the third component in PM6:Y6 system reveals efficient exciton dissociation feature in ternary organic solar cells. Nonradiative recombination losses are reduced, resulting in an improved power conversion efficiency in organic solar cells.

Abstract

The achievement of high performance in organic solar cells (OSCs) is highly dependent on efficient exciton dissociation. However, a comprehensive understanding of the exciton dissociation process under photoexcitation in OSCs remains elusive. Herein, a prototypical system of PM6:Y6 is adopted to explore the exciton dissociation process. An organic semiconductor PCz with distinctive photoexcitation signals from PM6 and Y6 is incorporated as the third component. Femtosecond transient absorption spectroscopy demonstrates clear cascade charge transfer processes in ternary PM6:PCz:Y6 system. These cascade channels contribute to enhancing the efficiency of exciton dissociation. Consequently, the nonradiative recombination energy loss is reduced, resulting in an improved power conversion efficiency (PCE) of OSCs. Furthermore, the reduction of energy loss is verified in different OSCs. When PCz is introduced into the D18:L8-BO system, a low nonradiative recombination energy loss of 0.175 eV is demonstrated, contributing a PCE of over 19%. This work highlights that the insight of efficient exciton dissociation enables low nonradiative recombination losses for efficient OSCs.

A facile method for depositing multidimensional perovskite thin films is presented, incorporating phenethylammonium chloride (PEACl) treatment into the antisolvent step for 3D perovskite formation. Using multimodal in situ characterization, it is shown that PEACl slows crystal growth, resulting in reduced grain boundary recombination and improved device efficiency. PEACl also forms hydrophobic 2D structures, protecting the film from humidity-induced degradation.

Abstract

This work introduces a simplified deposition procedure for multidimensional (2D/3D) perovskite thin films, integrating a phenethylammonium chloride (PEACl)-treatment into the antisolvent step when forming the 3D perovskite. This simultaneous deposition and passivation strategy reduces the number of synthesis steps while simultaneously stabilizing the halide perovskite film and improving the photovoltaic performance of resulting solar cell devices to 20.8%. Using a combination of multimodal in situ and additional ex situ characterizations, it is demonstrated that the introduction of PEACl during the perovskite film formation slows down the crystal growth process, which leads to a larger average grain size and narrower grain size distribution, thus reducing carrier recombination at grain boundaries and improving the device's performance and stability. The data suggests that during annealing of the wet film, the PEACl diffuses to the surface of the film, forming hydrophobic (quasi-)2D structures that protect the bulk of the perovskite film from humidity-induced degradation.

A robust shield emerges on perovskite, crafted through the dance of nucleophilic addition, coordination, and polymerization with triphenylmethane triisocyanate. A high-melting-point organic promoter for air-doping bars ion diffusion in the transport layer. This duet yields >25 % efficient n-i-p perovskite solar cells, basking in operational stability at 65 °C.

Abstract

Formamidinium lead triiodide serves as the optimal light-absorbing layer in single-junction perovskite solar cells. However, achieving operational stability of high-efficiency n-i-p type devices at elevated temperatures remains challenging. In this work, we implemented effective surface modifications on microcrystalline perovskite films. This involved the nucleophilic addition of formamidinium cations and coordination of residual PbI₂ with triphenylmethane triisocyanate as well as subsequent polymerization. The in situ growth of a cross-linking network chemically anchored on the perovskite film in this approach effectively reduced trap densities, favorably altered surface work function, suppressing interface charge recombination and thus enhancing cell efficiency. Coupled with a high-melting-point air-doping promoter, we fabricated n-i-p type perovskite solar cells surpassing 25 % efficiency, demonstrating excellent operational stability at 65 °C.

Nature Energy, Published online: 28 February 2024; doi:10.1038/s41560-024-01470-5

CsPb₂Br₅ that acts as a 2D seed is proposed for fabricating high-quality perovskite films and efficient perovskite solar cells. The formation energy of perovskite significantly reduces according to the density functional theory calculations. A precursor solution with 30% concentration identifies the longest charge lifetime and a remarkable power conversion efficiency of 24.06% is obtained.

Crystallization is a crucial step in obtaining high-quality perovskite films. A 2D seed-induced method is proposed for fabricating perovskite solar cells (PSCs). CsPb₂Br₅ significantly reduces the formation energy of perovskite according to the density functional theory calculations. The creation of perovskites is facilitated by CsPb₂Br₅, which also helps to improve the conditions for perovskite formation. The creation of large perovskite particles is accelerated by using a 2D seed-precursor solution, which also improves the performance of PbI₂ thin films. However, excessive doping can cause dopants to precipitate on the smooth surface of PbI₂ thin films, resulting in the formation of perovskite thin films with numerous cracks, ultimately reducing device efficiency. Through meticulous optimization, the perovskite thin film obtained from a precursor solution with 30% concentration identifies the longest charge lifetime. With a remarkable power conversion efficiency of 24.06% under one solar illumination, the champion gadget demonstrates extraordinary photovoltaic performance. These results offer important insights for the logical design and manufacture of perovskite materials and have the potential to significantly advance PSC technology.

Nature Energy, Published online: 26 February 2024; doi:10.1038/s41560-024-01471-4

This review highlights the stability challenges for the highly efficient perovskite–Si tandem solar cell. This article presents insight into tandem configuration challenges, namely, the significant thermal mismatch between the top perovskite and bottom Si solar cell, phase segregation in perovskites, strain in perovskites, and textured Si bottom cell besides other field-test scenarios along with their solutions.

As the balance of system cost of photovoltaic (PV) installations governs the competitiveness of PV device market, next-generation solar cells desire substantially enhanced power conversion efficiencies (PCEs). The single-junction perovskite and Si solar cells have demonstrated PCEs beyond 26% and 25%, respectively. The tandem configuration has crossed the threshold posed by the shockley queisser limit by demonstrating the 33.9% PCE. However, the unresolved issues in the perovskite community from a stability perspective pose challenges for realizing highly efficient and stable perovskite–Si tandem solar cells (TSCs). This review highlights the current status of perovskite–Si TSC from a stability perspective besides elucidating the degradation mechanisms at the perovskite–Si at the cell and module level. A highly efficient perovskite–Si TSC needs optimization keeping view the specific requirements for tandem configuration like strain, current matching, and bandgap optimization between the top perovskite and bottom Si subcell. Various stressors affecting the efficiency of the perovskite–Si module, namely, reverse bias and hot spot formation, and delamination, highlight valuable insight to develop future strategies for the perovskite–Si TSC. Stability regimes for the single-junction perovskite solar cell can provide the essential stepping stone but, modified stability regimes are inevitable.

The effects of a series of pyridine-derivative isomers containing both amino and carboxyl on the quality and stability of wide-bandgap perovskite are studied. The isomer with uniform functional group distribution delivers the best performance. A certified cell efficiency of 22.17% is obtained using the 1.68 eV perovskite, which is one of the highest values in wide-bandgap perovskite solar cells.

Abstract

Light-induced phase segregation is one of the main issues restricting the efficiency and stability of wide-bandgap perovskite solar cells (WBG PSCs). Small organic molecules with abundant functional groups can passivate various defects, and therefore suppress the ionic migration channels for phase segregation. Herein, a series of pyridine-derivative isomers containing amino and carboxyl are applied to modify the perovskite surface. The amino, carboxyl, and N-terminal of pyridine in all of these molecules can interact with undercoordinated Pb²⁺ through coordination bonds and suppress halide ions migration via hydrogen bonding. Among them, the 5-amino-3-pyridine carboxyl acid (APA-3) treated devices win the champion performance, enabling an efficiency of 22.35% (certified 22.17%) using the 1.68 eV perovskite, which represents one of the highest values for WBG-PSCs. This is believed to be due to the more symmetric spatial distribution of the three functional groups of APA-3, which provides a better passivation effect independent of the molecular arrangement orientation. Therefore, the APA-3 passivated perovskite shows the slightest halide segregation, the lowest defect density, and the least nonradiative recombination. Moreover, the APA-3 passivated device retains 90% of the initial efficiency after 985 h of operation at the maximum power point, representing the robust durability of WBG-PSCs under working conditions.

A facile post-treatment method is developed to fabricate efficient inorganic perovskite solar cells (IPSCs) by dynamically spin-coating 3-amino-5-bromopyridine-2-formamide (ABF) in methanol on the surface of CsPbI_2.85Br_0.15 film. A record-high efficiency of 20.80 % for p-i-n single-junction IPSCs was obtained (certified efficiency of 20.02 %). Furthermore, an inorganic perovskite/silicon tandem solar cell was successfully demonstrated, with an impressive efficiency of 26.26 %.

Abstract

Inorganic perovskite solar cells (IPSCs) have gained significant attention due to their excellent thermal stability and suitable band gap (~1.7 eV) for tandem solar cell applications. However, the defect-induced non-radiative recombination losses, low charge extraction efficiency, energy level mismatches, and so on render the fabrication of high-efficiency inverted IPSCs remains challenging. Here, the use of 3-amino-5-bromopyridine-2-formamide (ABF) in methanol was dynamically spin-coated on the surface of CsPbI_2.85Br_0.15 film, which facilitates the limited etching of defect-rich subsurface layer, resulting in the formation of vertical PbI₂ nanosheet structures. This enabled localized contacts between the perovskite film and the electron transport layer, suppress the recombination of electron-hole and beneficial to electron extraction. Additionally, the C=O and C=N groups in ABF effectively passivated the undercoordinated Pb²⁺ at grain boundaries and on the surface of CsPbI_2.85Br_0.15 film. Eventually, we achieved a champion efficiency of 20.80 % (certified efficiency of 20.02 %) for inverted IPSCs with enhanced stability, which is the highest value ever reported to date. Furthermore, we successfully prepared p-i-n type monolithic inorganic perovskite/silicon tandem solar cells (IPSTSCs) with an efficiency of 26.26 %. This strategy provided both fast extraction and efficient passivation at the electron-selective interface.

To address severe issues in NiO_x-based perovskite solar cells, different kinds of amino acids are introduced at NiO_x/perovskite interface. Research shows the L-tryptophan with two kinds of charged groups has the superior dual-passivation effect. With L-tryptophan, the quality of NiO_x and perovskite is improved. Besides, the performance and stability of devices is enhanced significantly.

Abstract

Nickel oxide (NiO_x) has been limited in use as a hole transport layer for its low conduction, surface defects, and redox reactions with the perovskite layer. To address these issues, the incorporation of zwitterion L-tryptophan (Trp) is proposed at the NiO_x/Trp interface. The carboxyl group of Trp effectively passivates the surface positive defects of NiO_x, thereby improving its optical and electrical properties. The ammonium group of Trp not only passivates negative defects but modulates the growth of the perovskite layer, resulting in an improved perovskite film quality. Furthermore, the Trp layer acts as a buffer layer, suppressing adverse interfacial reactions between the perovskite and NiO_x. Consequently, perovskite solar cells with 1.56 and 1.68 eV absorbers achieve the champion power conversion efficiency (PCE) of 23.79% and 20.41%, respectively. Moreover, the unencapsulated devices demonstrate excellent long-term stability, retaining above 80% of the initial PCE value after 1600 h of storage in the air with a humidity of 50–60%.

An accurate and rapid computational method is developed to predict the energy levels of nonfullerene acceptors, yielding smaller prediction errors than previous computation methods. The accurate prediction is enabled by the combination of a data-cleansing protocol that can effectively eliminate problematic experimental and a sub-unit-based molecular description method that greatly simplifies the complexity of molecular representations and hence the relevant molecular computation.

Abstract

Non-fullerene acceptors (NFAs) have recently emerged as pivotal materials for enhancing the efficiency of organic solar cells (OSCs). To further advance OSC efficiency, precise control over the energy levels of NFAs is imperative, necessitating the development of a robust computational method for accurate energy level predictions. Unfortunately, conventional computational techniques often yield relatively large errors, typically ranging from 0.2 to 0.5 electronvolts (eV), when predicting energy levels. In this study, the authors present a novel method that not only expedites energy level predictions but also significantly improves accuracy , reducing the error margin to 0.06 eV. The method comprises two essential components. The first component involves data cleansing, which systematically eliminates problematic experimental data and thereby minimizes input data errors. The second component introduces a molecular description method based on the electronic properties of the sub-units comprising NFAs. The approach simplifies the intricacies of molecular computation and demonstrates markedly enhanced prediction performance compared to the conventional density functional theory (DFT) method. Our methodology will expedite research in the field of NFAs, serving as a catalyst for the development of similar computational approaches to address challenges in other areas of material science and molecular research.

This study presents an innovative strategy, employing both gas quenching technology and ultrasonic-assisted processing (UAP), to fabricate high-caliber perovskite thin films. The UAP promotes the growth of nuclei by enhancing mass and heat transfer through microscopic mixing that improves the film quality. Ultimately, the inverted perovskite solar cells with a champion efficiency of 24.5% are successfully demonstrated.

Abstract

In recent years, perovskite solar cells have attained unprecedented advancements in power conversion efficiency, yet their commercialization remains a formidable challenge. Addressing this challenge relies on developing an affordable and scalable method for manufacturing top-notch perovskite films. This study presents an innovative strategy, employing both gas quenching technology and ultrasonic-assisted processing (UAP), to fabricate high-caliber perovskite thin films. The UAP process enhances the grain size of the perovskite film, reduces grain boundary defects, improves carrier extraction and transport, and suppresses carrier nonradiative recombination. Furthermore, it effectively reduces residual stress and mitigates lattice distortion in the perovskite crystals. Ultimately, efficient and stable inverted perovskite solar cells using FA_0.87Cs_0.13PbI_2.7Br_0.3 and FA_0.85MA_0.1Cs_0.05PbI₃ perovskite are successfully prepared. The target device achieved a power conversion efficiency of 22.32% and 24.51%, respectively. Moreover, the target devices exhibited enhanced photostability. This work provides a cost-effective and scalable method for producing high-quality perovskite films, paving the way for the commercialization of perovskite solar cells.

This study addresses the challenge of maintaining efficiency in thick-film organic solar cells (OSCs). A novel polymer adsorption strategy that regulates molecular stacking, leading to enhanced intermolecular interactions. A reduction in trap states and an elongation in exciton diffusion length, resulting in a remarkable increase in power conversion efficiency in thick-film OSCs, is achieved.

Abstract

Developing efficient organic solar cells (OSCs) with thick active layers is crucial for roll-to-roll printing. However, thicker layers often result in lower efficiency. This study tackles this challenge using a polymer adsorption strategy combined with a layer-by-layer approach. Incorporating insulator polystyrene (PS) into the PM6:L8-BO system creates PM6+PS:L8-BO blends, effectively suppressing trap states and extending exciton diffusion length in the mixed donor domain. Adding insulating polymers with benzene rings to the donor enhances π–π stacking of donors, boosting intermolecular interactions and electron wave function overlap. This results in more orderly molecular stacking, longer exciton lifetimes, and higher diffusion lengths. The promoted long-range exciton diffusion leads to high power conversion efficiencies of 19.05% and 18.15% for PM6+PS:L8-BO blend films with 100 and 300 nm thickness, respectively, as well as a respectable 16.00% for 500 nm. These insights guide material selection for better exciton diffusion, and offer a method for thick-film OSC fabrication, promoting a prosperous future for practical OSC mass production.

We developed a new D-π-A type polymer donor QQ1 via introducing a dithienoquinoxalineimide (DTQI) A unit. The binary QQ1 : PY-IT and ternary QQ1 : PY-IT : F-BTA3 all-PSCs present high PCEs of 18.81 % and 19.20 % respectively, benefiting from broad absorption range, reduced energy loss, and compact π–π stacking. These results provide new insight in the rational design of novel nonhalogenated polymer donors for further development of all-PSCs.

Abstract

All-polymer solar cells (all-PSCs) have been regarded as one of the most promising candidates for commercial applications owing to their outstanding advantages such as mechanical flexibility, light weight and stable film morphology. However, compared to large amount of new-emerging excellent polymer acceptors, the development of high-performance polymer donor lags behind. Herein, a new D-π-A type polymer donor, namely QQ1, was developed based on dithienoquinoxalineimide (DTQI) as the A unit, benzodithiophene with thiophene-conjugated side chains (BDTT) as the D unit, and alkyl-thiophene as the π-bridge, respectively. QQ1 not only possesses a strong dipole moment, but also shows a wide band gap of 1.80 eV and a deep HOMO energy level of −5.47 eV, even without halogen substituents that are commonly indispensable for high-performance polymer donors. When blended with a classic polymer acceptor PY-IT, the QQ1-based all-PSC delivers an outstanding PCE of 18.81 %. After the introduction of F-BTA3 as the third component, a record PCE of 19.20 % was obtained, the highest value reported so far for all-PSCs. The impressive photovoltaic performance originates from broad absorption range, reduced energy loss, and compact π–π stacking. These results provide new insight in the rational design of novel nonhalogenated polymer donors for further development of all-PSCs.

Publication date: April 2024

Source: Applied Materials Today, Volume 37

Author(s): Bonsa Regassa Hunde, Abraham Debebe Woldeyohannes, Getachew Adam Workneh

A novel dibenzo[g,p]chrysene-based HTM is synthesized with peripheral methoxy- and methylthio-groups, which endow them with appropriate energy levels, high-hole mobility, and enhanced interfacial interactions. This results in a remarkable certified power conversion efficiency of 24.89% for n-i-p devices. The larger-scale PSC (1.0 cm²) and module (29.0 cm²) yield PCEs of 23.57 and 20.22%, respectively.

Abstract

Hole-transporting materials (HTMs) are indispensable for realizing efficient and stable perovskite solar cells (PSCs). Herein, a novel dibenzo[g,p]chrysene-based HTM, termed FTPE-OSMe, is synthesized with peripheral methoxy- and methylthio-groups, which contrasts with most other small molecule HTMs that feature only methoxy-groups. The presence of methoxy- and methylthio-groups endows FTPE-OSMe with appropriate energy levels, high-hole mobility and enhanced interfacial interactions. PSCs employing Li-TFSI and 4-tert-butylpyridine-doped FTPE-OSMe demonstrate a remarkable power conversion efficiency (PCE) of 24.94% (certified 24.89%). The larger-scale PSC (1.0 cm²) and module (29.0 cm²) yield PCEs of 23.57 and 20.22%, respectively. In addition, the dopant-free FTPE-OSMe-based PSCs exhibit a respectable PCE of 22.40% and excellent stability.

Giant molecular acceptors are typically designed with different linkers to tune their intermolecular and intramolecular interactions. Unlike prior approaches using p-type linkers, here we explore an n-type linker, notably the benzothiadiazole unit, affording BT-DL via a click-like Knoevenagel condensation. It exhibits stronger intramolecular super-exchange coupling compared to its benzene-linked counterpart, leading to better device efficiency.

Abstract

Giant molecular acceptors (GMAs) are typically designed through the conjugated linking of individual small molecule acceptors (SMAs). This design imparts an extended molecular size, elevating the glass transition temperature (T _g) relative to their SMA counterparts. Consequently, it effectively suppresses the thermodynamic relaxation of the acceptor component when blended with polymer donors to construct stable polymer solar cells (PSCs). Despite their merits, the optimization of their chemical structure for further enhancing of device performance remains challenge. Different from previous reports utilizing p-type linkers, here, we explore an n-type linker, specifically the benzothiadiazole unit, to dimerize the SMA units via a click-like Knoevenagel condensation, affording BT-DL. In comparison with B-DL with a benzene linkage, BT-DL exhibits significantly stronger intramolecular super-exchange coupling, a desirable property for the acceptor component. Furthermore, BT-DL demonstrates a higher film absorption coefficient, redshifted absorption, larger crystalline coherence, and higher electron mobility. These inherent advantages of BT-DL translate into a higher power conversion efficiency of 18.49 % in PSCs, a substantial improvement over the 9.17 % efficiency observed in corresponding devices with B-DL as the acceptor. Notably, the BT-DL based device exhibits exceptional stability, retaining over 90 % of its initial efficiency even after enduring 1000 hours of thermal stress at 90 °C. This work provides a cost-effective approach to the synthesis of n-type linker-dimerized GMAs, and highlight their potential advantage in enhancing intramolecular coupling for more efficient and durable photovoltaic technologies.

A previous study showed that blending octylammonium iodide (OAI) to carbon paste induced a kind of “in-situ healing” effect for “perovskite / carbon” interface. Here the mechanism of this effect is explored by careful examination of the interaction between OAI molecule and carbon black (CB) nanoparticles. Mass ratio tuning experiment between OAI and CB, and shelf-stability test come to show that, the famous “CB adsorption” causes a kind of “slow-release effect” during the healing processes. PCE is optimized to > 19% by adjusting the mass ratio between OAI and CB, as well as light harvesting ability of the perovskite layer.

Abstract

“Perovskite / Carbon” interface has remained a key bottleneck for the hole-conductor-free perovskite solar cells based on carbon-electrode (CPSCs), due to problems like loose physics contact, defects, energy mismatch, poor chemical coupling, etc. A previous study shows that octylammonium iodide (OAI) blending in carbon paste induced a kind of “in-situ healing” effect for “perovskite / carbon” interface, and improved power conversion efficiency from ≈13% to >19%. Here the beneath mechanism is further explored by careful examination of the interaction between OAI molecule and carbon black (CB) nanoparticles. It comes to show that, the famous “CB adsorption” plays a key role during the “healing” processes. Due to CB adsorption behavior, the mass ratio between OAI and CB influences much on the healing effect. By suitably adjusting the mass ratio between OAI and CB, and increasing the light harvest of perovskite, an efficiency of 19.41% is achieved for the hole-conductor-free CPSCs. Device efficiency and the charge-extraction and recombination process are tracked with the storage period, continuous improvement appears for devices assembled by relatively higher CB mass. A kind of “slow-release effect” is revealed during the OAI-induced “in-situ healing” process, which is caused by the famous “CB adsorption” behavior.

Nature, Published online: 21 February 2024; doi:10.1038/s41586-024-07189-3