Chen Weijie

In this work, a self-assembled bilayer comprising a covalent monolayer (Br-2PACz) and a wetting layer (4CzNH₃I) as HTL in a Sn/Pb perovskite solar cell is implemented. It is demonstrated that the 4CzNH₃I layer completely solves the wettability problem due to the higher polarity of the newly formed surface. The NH₃ ⁺ groups also help in the passivation of the buried interface.

Abstract

Recently, carbazole-based self-assembled monolayers (SAMs) have been utilized as hole transport layers (HTLs) in perovskite solar cells. However, their application in Sn or mixed Sn/Pb perovskite solar cells has been hindered by the poor wettability of the perovskite precursor solution on the carbazole surface. Here a self-assembled bilayer (SAB) comprising a covalent monolayer (Br-2PACz) and a noncovalent wetting layer (4CzNH₃I) as the HTL in a Cs_0.25FA_0.75Sn_0.5Pb_0.5I₃ perovskite solar cell is proposed. It is demonstrated that the wetting layer completely solves the problem due to the higher polarity of the surface and, furthermore, the ammonium groups help in the passivation of trap states at the buried SAB/perovskite interface. The introduction of the SAB enhances the device reproducibility with an average efficiency of 18.98 ± 0.28% (19.45% for the best device), compared to 11.54 ± 9.36% (19.34% for the best device) for the SAM-only devices. Furthermore, the improved perovskite processability on the SAB helps to increase the reproducibility of larger size device, where, a 12.5% efficiency for a 0.8 cm² active area device compared to 0.68% for the best SAM-based solar cell is demonstrated. Finally, the device's operational stability is also improved to 358 hours (T_80%), compared to 220 hours for the SAM-based solar cell.

Publication date: October 2023

Source: Applied Materials Today, Volume 34

Author(s): Woraprom Passatorntaschakorn, Warunee Khampa, Wongsathon Musikpan, Chawalit Bhoomanee, Athipong Ngamjarurojana, Sakhorn Rimjaem, Atcharawon Gardchareon, Chatchai Rodwihok, Han S. Kim, Nutcha Khambunkoed, Ratchadaporn Supruangnet, Hideki Nakajima, Ladda Srathongsian, Pongsakorn Kanjanaboos, Akarin Intaniwet, Anusit Kaewprajak, Pisist Kumnorkaew, Fabrice Goubard, Pipat Ruankham, Duangmanee Wongratanaphisan

A novel method is uncovered for in situ generation of I₃ ⁻ via doping 4-(chlorosulfonyl)benzoic acid into CsPbI₂Br and suppress the light-soaking effect of solar cells through zwitterionic passivation. This work offers a deep opinion for future researchers to modulate the light-soaking effect of all-inorganic perovskite solar cells.

The light-soaking (LS) effect has been reported to limit the accuracy and stability of device power output of perovskite solar cells (PSCs) and it is significant to develop effective approaches and strategies to eliminate the LS effect in PSCs. There are very few reports on suppressing the LS effect in CsPbI₂Br-based all-inorganic PSCs. Herein, a method to eliminate the LS effect by synchronous passivation of anionic and cationic defects in CsPbI₂Br perovskite film is demonstrated. The 4-(chlorosulfonyl)benzoic acid (CSBA) is added into perovskite precursor and the in situ generation of I₃ ⁻ effectively passivates the anionic halogen vacancy defects in CsPbI₂Br. In the meantime, the Lewis base groups on CSBA coordinate with Cs⁺ and Pb²⁺ to passivate the cationic defects. This zwitterionic passivation effect of CSBA remarkably cuts off the path of defect-induced charge recombination and thus eliminates the LS effect. This work offers a deep opinion for future researchers to modulate the LS effect of all-inorganic PSCs.

Nonuniform strain in perovskite thin films, stemming from factors like thermal expansion mismatch and deposition conditions, significantly impairs optical and electronic properties, undermining structural integrity and resulting in device failure. Moreover, successful perovskite photoelectric device advancement necessitates an in-depth understanding of strain effects, enabling the amelioration of stability-related challenges and the optimization of performance.

Perovskite solar cells (PSCs) are regarded as the most promising new generation of green energy technology due to their outstanding device performance and simple processing technology. The strain in the active layer of PSCs is primarily caused by lower interionic and intercrystal forces, leading to an increase in defect density and high recombination of carriers, which can negatively impact the performance and stability of perovskite devices. Herein, the origins of strain in perovskite film of solution processing are revealed by conducting strain tests and characterizing photophysical processes. The impacts of strain on optical and electrical properties are summarized, including its effects on molecular interaction force, band structure, defect formation energy, activation energy of ion migration, phase segregation, and phase transition. To mitigate these negative effects, the review introduces several methods for modulating strain in perovskite films, including crystallization, component tailoring, adding additives, and modifying contact layers, which are aimed at improving carrier transport and collection efficiency. It is believed that these approaches will provide scientists with new ways of thinking and system schemes for improving the performance and stability of perovskite solar cells.

The crystallization dynamics of α-formamidinium lead triiodide (α-FAPbI₃) perovskites during ambient blade coating are manipulated by employing an additive 1-butylpyridine tetrafluoroborate (BPyBF₄), resulting in the highly crystalline perovskite film with large grains, eliminated voids, and reduced defects. This enables the high power conversion efficiencies of 23.50% and 21.60% for a 0.09 cm² area device and a 5 cm × 5 cm-area module, respectively.

Abstract

Upscalable printing of high-performance and stable perovskite solar cells (PSCs) is highly desired for commercialization. However, the efficiencies of printed PSCs lag behind those of their lab-scale spin-coated counterparts owing to the lack of systematic understanding and control over perovskite crystallization dynamics. Here, the controlled crystallization dynamics achieved using an additive 1-butylpyridine tetrafluoroborate (BPyBF₄) for high-quality ambient printed α-formamidinium lead triiodide (FAPbI₃) perovskite films are reported. Using in situ grazing-incidence wide-angle X-ray scattering and optical diagnostics, the spontaneous formation of α-FAPbI₃ from precursors during printing without the involvement of  δ-FAPbI₃ is demonstrated. The addition of BPyBF₄ delays the crystallization onset of α-FAPbI₃, enhances the conversion from sol-gel to perovskite, and reduces stacking defects during printing. Therefore, the altered crystallization results in fewer voids, larger grains, and less trap-induced recombination loss within printed films. The printed PSCs yield high power conversion efficiencies of 23.50% and 21.60% for a 0.09 cm^–2area device and a 5 cm × 5 cm-area module, respectively. Improved device stability is further demonstrated, i.e., approximately 94% of the initial efficiency is retained for over 2400 h under ambient conditions without encapsulation. This study provides an effective crystallization control method for the ambient printing manufacture of large-area high-performance PSCs.

We synthesized three 3D four-arm small molecules with spirobifluorene as the central core and different end-group-modified benzotriazole units as arms. By incorporating four-arm molecules, PM6 : Y6-based ternary organic solar cells (OSCs) achieved improved efficiencies of 18.7–19.1 %, benefiting from triggered multiple mechanisms and the inhibited excessive aggregation of Y6. Our results open a new avenue for the design of promising guest molecules for ternary OSCs.

Abstract

A third component featuring a planar backbone structure similar to the binary host molecule has been the preferred ingredient for improving the photovoltaic performance of ternary organic solar cells (OSCs). In this work, we explored a new avenue that introduces 3D-structured molecules as guest acceptors. Spirobifluorene (SF) is chosen as the core to combine with three different terminal-modified (rhodanine, thiazolidinedione, and dicyano-substituted rhodanine) benzotriazole (BTA) units, affording three four-arm molecules, SF-BTA1, SF-BTA2, and SF-BTA3, respectively. After adding these three materials to the classical system PM6 : Y6, the resulting ternary devices obtained ultra-high power-conversion efficiencies (PCEs) of 19.1 %, 18.7 %, and 18.8 %, respectively, compared with the binary OSCs (PCE=17.4 %). SF-BTA1-3 can work as energy donors to increase charge generation via energy transfer. In addition, the charge transfer between PM6 and SF-BTA1-3 also acts to enhance charge generation. Introducing SF-BTA1-3 could form acceptor alloys to modify the molecular energy level and inhibit the self-aggregation of Y6, thereby reducing energy loss and balancing charge transport. Our success in 3D multi-arm materials as the third component shows good universality and brings a new perspective. The further functional development of multi-arm materials could make OSCs more stable and efficient.

Efficient and photostable furan-based n-type semiconductors were developed for organic solar cells. Important photodegradation mechanisms were revealed and analyzed and the findings lead to effective strategies to improve the photostability of non-fullerene electron acceptors.

Abstract

We explore a series of furan-based non-fullerene acceptors and report their optoelectronic properties, solid-state packing, photodegradation mechanism and application in photovoltaic devices. Incorporating furan building blocks leads to the expected enhanced backbone planarity, reduced band gap and red-shifted absorption of these acceptors. Still, their position in the molecule is critical for stability and device performance. We found that the photodegradation of these acceptors originates from two distinct pathways: electrocyclic photoisomerization and Diels–Alder cycloaddition of singlet oxygen. These mechanisms are of general significance to most non-fullerene acceptors, and the photostability depends strongly on the molecular structure. Placement of furans next to the acceptor termini leads to better photostability, well-balanced hole/electron transport, and significantly improved device performance. Methylfuran as the linker offers the best photostability and power conversion efficiency (>14 %), outperforming all furan-based acceptors reported to date and all indacenodithiophene-based acceptors. Our findings show the possibility of photostable furan-based alternatives to the currently omnipresent thiophene-based photovoltaic materials.

Publication date: November 2023

Source: Nano Energy, Volume 116

Author(s): Chao Gao, Haotian Zhang, Feiyang Qiao, Huanpei Huang, Dezhao Zhang, Dong Ding, Daxue Du, Jingjing Liang, Jiahao Bao, Hong Liu, Wenzhong Shen

There is a lattice mismatch between the α-phase FAPbI₃ perovskite and the δ-phase impurity. It generates strong microstrain in perovskite film and accelerates the aging of perovskite. Introducing Cs ions decreases the lattice mismatch and improves the device stability accordingly.

Lattice strain is often regarded as an important factor affecting the stability of organic–inorganic hybrid perovskite solar cells, but the current understanding on the origin of the strain is still unclear. Herein, the microstructure of formamidinium perovskite is analyzed by the Rietveld refinement method to reveal the origin of its microstrain. It is found that there is a lattice mismatch between the α-phase perovskite and the δ-phase impurity during the fabrication process, which generates strong microstrain in perovskite film. Moreover, the strain also exacerbates the aging process of formamidinium perovskite. By introducing Cs ions, the lattice mismatch of α-phase and δ-phase perovskites is reduced, thereby reducing the microstrain of perovskites and improving the device performance.

An efficient perovskite/TiO₂ heterojunction is constructed by adding TiO₂ to an antisolvent to concurrently form a perovskite layer and a top TiO₂ electron transport layer in one step, which significantly improves the interfacial contact and thus facilitates charge transport at the heterojunction. The resultant inverted all-layer-inorganic CsPbI₂Br device achieves a superior efficiency of 17.1% and excellent stability.

Abstract

All-layer-inorganic perovskite solar cells (PSCs) are prized for their remarkable thermal stability and low cost. However, “imperfect contact” at the perovskite heterojunction hinders charge transport and causes photochemical deterioration, restricting photovoltaic performance, and operational stability. Herein, an efficient perovskite/TiO₂ heterojunction is constructed, produced by adding TiO₂ to an antisolvent to concurrently form a CsPbI₂Br perovskite layer and a top TiO₂ electron transport layer in one step, which significantly improves the interfacial contact and thus facilitates charge transport at the heterojunction. The resultant inverted all-layer-inorganic PSCs exhibit a superior efficiency of 17.1%. Moreover, given the high-quality perovskite/TiO₂ heterojunction and low interface defects, the encapsulated PSCs retain 91% or 92% of their initial efficiency for 1000 h under maximum power point tracking or damp-heat conditions (85 °C and 85% relative humidity), respectively. Surprisingly, the unencapsulated PSCs maintain an initial efficiency of 86% during aging, even at 200 °C for 200 h.

Publication date: October 2023

Source: Nano Energy, Volume 115

Author(s): Ruihao Chen, Yang Yang, Zhiyuan Dai, Li Yuan, Jieru Du, Penghui Yang, Yuyao Yang, Hui Shen, Zhe Liu, Hongqiang Wang

In this study, the interface passivation capability of different chalcogenide-based molecules is investigated. It is observed that compared to oxygen-based passivators, the sulfur, and selenium-based molecules are more effective in passivating the interfacial defects and enhancing the stability of perovskite solar cells.

Abstract

Chalcogenide-based Lewis bases are widely used in perovskite solar cells (PSCs) due to their effectiveness in passivating Pb²⁺ and Pb⁰-related defects. However, the underlying principles governing their defect passivation and the relative efficacy of different chalcogen elements remain poorly understood. This study evaluates the effectiveness of oxygen, sulfur, and selenium-based interface passivator molecules in enhancing the stability and power conversion efficiency (PCE) of perovskite solar cell devices. The hard and soft acid and base (HSAB) principle has been utilized here to gain insights into the defect passivation behavior of chalcogenide-based molecules. The photoluminescence, ideality factor, and trap density measurements reveal that the sulfide and selenide-passivated devices exhibit superior defect passivation compared to the oxide-passivated control device. In terms of stability, the average T₇₅ lifetime (time at which 75% of the initial PCE is retained) of the oxide, sulfide, and selenide passivated samples is 6%, 30%, and 50% higher compared to their un-passivated counterparts. This enhanced stability with the sulfide and selenide-based passivators can be attributed to their soft Lewis base nature, which resulted in stronger interaction with the Pb-related defects, as evidenced by the density-functional theory calculations and X-Ray photoelectron spectroscopy study.

Highly efficient and stable, rigid and flexible p-i-n perovskite solar cells are developed by incorporating a 2-(acetyloxy)-N,N,N-trimethylethanium chloride additive into the lead iodide precursor solution to prepare a porous PbI₂ layer. The good diffusion of the organic ammonium salt results in flat and dense perovskite film with large particle size, which achieves high power conversion efficienciesPCE of 23.40% (rigid) and 21.10% (flexible) with excellent ambient and mechanical stability.

Abstract

Flexible perovskite solar cells (FPSCs) are attracting widespread research and attention for their benefits as the next-generation wearable electronic products. However, there are still many challenges in the quest to achieve dense, pinhole-free, high crystal quality, low defect, and stable perovskite films, which limit further improvement in the efficiency and stability of FPSCs. Herein, a novel technique for the incorporation of quaternary ammonium halide (QAH) additives to prepare fluffy porous lead iodide layers by using a two-step sequential deposition method, is reported. Benefiting from the good diffusion of organic amine salts on porous PbI₂ layers, flat and dense perovskite films are produced with large particle sizes, few defects, and high crystal quality. Finally, the champion rigid and flexible p-i-n PSCs with the 2-(acetyloxy)-N,N,N-trimethylethanium chloride (AtaCl) additive achieves exciting power conversion efficiencies (PCE) of 23.40% and 21.10%, respectively. The device with the AtaCl additive retains over 90% of its original PCE under ambient conditions (40 ± 5% relative humidity (RH)) over 1000 h of aging without encapsulation. In addition, the flexible device with the AtaCl additive shows excellent stability under mechanical bending conditions, retaining ≈85% of its original PCE after 10 000 cycles (bending radius = 5 mm).

The hot-casting strategy assists in the fast and synchronous molecular assembly in the active layer, which contributes to preferable vertical phase separation, donor/acceptor ratio, and molecular stacking. The profitable morphology is beneficial to charge generation and extraction, leading to top-ranked device efficiencies based on different matrixes and high-boiling solvents.

Abstract

Most top-rank organic solar cells (OSCs) are manufactured by the halogenated solvent chloroform, which possesses a narrow processing window due to its low-boiling point. Herein, based on two high-boiling solvents, halogenated solvent chlorobenzene (CB) and non-halogenated green solvent ortho-xylene (OX), preparing active layers with the hot solution is put forward to enhance the performance of the OSCs. In situ test and morphological characterization clarify that the hot-casting strategy assists in the fast and synchronous molecular assembly of both donor and acceptor in the active layer, contributing to preferable donor/acceptor ratio, vertical phase separation, and molecular stacking, which is beneficial to charge generation and extraction. Based on the PM6:BO-4Cl, the hot-casting OSCs with a wide processing window achieve efficiencies of 18.03% in CB and 18.12% in OX, which are much higher than the devices processed with room temperature solution. Moreover, the hot-casting devices with PM6:BTP-eC9 deliver a remarkable fill factor of 80.31% and efficiency of 18.52% in OX, representing the record value among binary devices with green solvent. This work demonstrates a facile strategy to manipulate the molecular distribution and arrangement for boosting the efficiency of OSCs with high-boiling solvents.

Nature, Published online: 09 August 2023; doi:10.1038/s41586-023-06514-6

This innovative solution demonstrates a new process for the stabilization of CsPbI_3−x Br _x perovskites at the lower annealing temperature of 180 °C, thanks to a rational halide substitution enabled by the introduction of mixed halide dimethylammonium additives. This approach allows the fabrication of mesoscopic n–i–p CsPbI_3−x Br _x solar cells, with a champion power conversion efficiency of 16.23%.

All-inorganic perovskites are a promising solution for the fabrication of thermally stable perovskite solar cells (PSCs) with remarkable performances. However, a high annealing temperature is required for the stabilization of the photoactive phase of CsPbI₃, which represents a limiting factor for their potential scaling-up and manufacturing at industrial scale. This work demonstrates a new process for the stabilization of CsPbI_3−x Br _x perovskite at lower annealing temperature of 180°, based on a rational halogen substitution enabled by the introduction of dimethylammonium (DMA) additives. Bromide inclusion favors indeed the conversion from the intermediate phases to CsPbI_3−x Br _x . Standard mesoscopic solar cells prepared with this approach achieve a power conversion efficiency (PCE) of 14.86%, with reduced voltage losses and increased fill factor compared to the reference device. Moreover, this work proves that a rational substitution of the halide in the DMA salt is also beneficial for the devices annealed at higher temperature, achieving an encouraging PCE of 16.23%. By reducing the processing temperature, this new method widens the range of applications of all-inorganic PSCs toward temperature-sensitive materials and industrial applications.

The stepwise method proposed to synthesize non-fullerene oligomer acceptors via consecutive Stille coupling reactions offers significant advantages compared to the traditional approach, resulting in fewer unwanted by-products and easier purification processes. By utilizing this method, the obtained Tri-Y6-OD-based organic solar cells achieved a high power conversion efficiency of 18.03 %, along with excellent stability.

Abstract

Oligomer acceptors have recently emerged as promising photovoltaic materials for achieving high power conversion efficiency (PCE) and long-term stability in organic solar cells (OSCs). However, the limited availability of diverse acceptors, resulting from the sole synthetic approach, has hindered their potential for future industrialization. In this study, we present a facile and effective stepwise approach that utilizes two consecutive Stille coupling reactions for the synthesis of oligomer acceptors. To demonstrate the feasibility of the novel approach, we successfully synthesize a trimer acceptor, Tri-Y6-OD, and further systematically investigate the impact of oligomerization on device performance and stability. The results reveal that this approach has significant advantages compared to the conventional method, including reduced formation of unwanted by-products and lower difficulties in purification. Remarkably, the OSC based on PM6 : Tri-Y6-OD achieves an impressive PCE of 18.03 % and maintains 80 % of the initial PCE (T ₈₀) for 1523 h under illumination, surpassing the performance of the corresponding small molecule acceptor Y6-OD-based device. Furthermore, the versatility of the synthetic strategy in obtaining diverse acceptors is further demonstrated. Overall, our findings provide a facile, versatile and stepwise way for synthesizing oligomer acceptors, thereby facilitating the development of stable and efficient OSCs.

Nature Energy, Published online: 08 August 2023; doi:10.1038/s41560-023-01330-8

This work presents a novel and effective mixed-cation passivation system (CE) to synergically passivate various types of traps in wide-Eg perovskite, resulting in a record open-circuit voltage (V _oc) of wide-Eg PVSCs (1.35 V) and a high fill factor (FF) of 83.29%. These improvements lead to a record PCE of 24.47% when applied to fabricated perovskite/organic tandem solar cells.

Abstract

Perovskite/organic tandem solar cells (POTSCs) are gaining attention due to their easy fabrication, potential to surpass the S-Q limit, and superior flexibility. However, the low power conversion efficiencies (PCEs) of wide bandgap (Eg) perovskite solar cells (PVSCs) have hindered their development. This work presents a novel and effective mixed-cation passivation strategy (CE) to passivate various types of traps in wide-Eg perovskite. The complementary effect of 4-trifluoro phenethylammonium (CF₃-PEA⁺, denoted as CA⁺) and ethylenediammonium (EDA²⁺, denoted as EA²⁺) reduces both electron/hole defect densities and non-radiative recombination rate, resulting in a record open-circuit voltage (V _oc) of wide-Eg PVSCs (1.35 V) and a high fill factor (FF) of 83.29%. These improvements lead to a record PCE of 24.47% when applied to fabricated POTSCs, the highest PCE to date. Furthermore, unencapsulated POTSCs exhibit excellent photo and thermal stability, retaining over 90% of their initial PCE after maximum power point (MPP) tracking or exposure to 60 °C for 500 h. These findings imply that the synergic effect of surface passivators is a promising strategy to achieve high-efficiency and stable wide-Eg PVSCs and corresponding POTSCs.

A series of new carboxylate-containing poly(thiophene vinylene)s (PETTCVT-X, X = L, M, and H) with different molecular weights (MWs) is developed. Intrinsically stretchable organic solar cells featuring the highest MW PETTCVT-H achieve the highest initial power conversion efficiency (PCE= 10.1%) and stretchability (strain at PCE_80% = 16%) among the series.

Abstract

Owing to their simple chemical structures and straightforward synthesis, poly(thiophene vinylene) (PTV) derivatives are promising types of polymer donors for organic solar cells (OSCs). However, the structural rigidity of PTVs results in the formation of films with poor mechanical properties, which limits the application of PTVs in intrinsically stretchable (IS)-OSCs. Here, new carboxylate-containing PTVs are developed with tuned molecular weight (MW) (PETTCVT-X, X = L, M, and H) and realize efficient and mechanically durable IS-OSCs. The crystallinity of the PTVs increases progressively with increasing MW, leading to enhanced hole mobility and suppressed charge recombination of the OSCs. Moreover, both the mechanical stretchability and electrical properties of the PTVs increase significantly with increasing MW, owing to the formation of tie-chains that connect the isolated crystalline domains. Consequently, OSCs featuring a PTV with the highest MW (PETTCVT-H) exhibit the highest power conversion efficiency (PCE, 15.3%) and crack-onset strain (COS, 7.1%) among the series, compared to lower values for the PETTCVT-L (PCE = 9.7% and COS = 1.3%) and PETTCVT-M-based OSCs (PCE = 12.5% and COS = 3.7%). Therefore, the IS-OSCs employing PETTCVT-H present the highest initial PCE (10.1%) and stretchability (strain at PCE_80% (retaining 80% of the initial PCE) = 16%).

The device physics of high-performance organic photodiodes and solar cells are analyzed before and after a short-pulse 170 keV proton irradiation with a fluence of 2·10¹² p cm⁻². The devices reveal a hitherto unknown self-healing effect during several days of storage in a dry nitrogen atmosphere at room temperature by reducing the proton-induced trap concentration in the bulk of the organic active layer.

Abstract

In this study, a comprehensive quantitative analysis of the photodiode (PD) is conducted and photovoltaic (PV) characteristics of organic non-fullerene PCE10:ITIC-4F devices before and after exposure to a 150 ns pulse of 170 keV proton irradiation with the fluence of 2·10¹² p cm⁻² that is equivalent to ≈6 years of operation at a low Earth orbit. While an expected initial performance reduction happened in the photodiode and photovoltaic operation modes, a hitherto unknown self-healing effect in the organic devices is observed several days after the proton irradiation. The organic bulk-heterojunction (BHJ) material properties and the multi-mechanisms recombination processes before and after irradiation and during self-healing are investigated. This analysis provides a quantitative understanding of the changes occurring in the device physics and points toward the relevant aspects of the self-healing mechanism related to the dynamics of proton-induced traps in the bulk of the organic active layer. Ultimately, the synergy of record lightweight features and newly discovered self-healing of proton-induced damage in organic PDs and solar cells highlights their great potential for applications in rapidly emerging space technology.

A highly efficient dye-sensitized indoor photovoltaic fiber is designed with a photoanode made from a hybrid TiO₂ layer on Ti wire and a counter electrode composed of an aligned carbon nanotube sheet on metal fiber, showing a certified power conversion efficiency of 25.53% under 1500 lux illuminance. These IPVFs can supply electricity for wearables, providing a mobile power solution indoors.

Abstract

Photovoltaic devices represent an efficient electricity generation mode. Integrating them into textiles offers exciting opportunities for smart electronic textiles—with the ultimate goal of supplying power for wearable technology—which is poised to change how electronic devices are designed. Many human activities occur indoors, so realizing indoor photovoltaic fibers (IPVFs) that can be woven into textiles to power wearables is critical, although currently unavailable. Here, a dye-sensitized IPVF is constructed by incorporating titanium dioxide nanoparticles into aligned nanotubes to produce close contact and stable interfaces among active layers on a curved fiber substrate, thus presenting efficient charge transport and low charge recombination in the photoanode. With the combination of highly conductive core–sheath Ti/carbon nanotube fiber as a counter electrode, the IPVF shows a certified power conversion efficiency of 25.53% under 1500 lux illuminance. Its performance variation is below 5% after bending, twisting, or pressing for 1000 cycles. These IPVFs are further integrated with fiber batteries as self-charging power textiles, which are demonstrated to effectively supply electricity for wearables, solving the power supply problem in this important direction.

Nature Communications, Published online: 07 August 2023; doi:10.1038/s41467-023-40421-8

Based on phenomenological studies, the range of reverse breakdown voltages of electron transport layer-free perovskite solar cells (PSCs) has been confirmed. It is discovered that PSCs exhibit dynamic reverse bias behavior which is distinct from that of conventional solar cells. A model to explain this behavior in conjunction with ion migration and drift diffusion is developed.

Perovskite solar cells (PSCs) have shown an impressive power conversion efficiency of 26.1%, while their upcoming commercialization urgently needs to solve the stability problem. Among numerous stability issues of PSCs, little attention is paid to reverse bias stability. When some cells of the module are shaded by irresistible factors, this will cause the current of the illuminated part to flow through the shaded cells as a reverse current and force them to be under reverse bias. Herein, the breakdown mechanism dominated by different reverse bias regions of a prototype electron transport layer free PSCs is distinguished. And, it is confirmed that PSCs present a thought-provoking dynamic reverse bias (DRB) behavior and variable reverse breakdown voltage (V _RB), which is essentially distinct from classic solar cells. Specifically, V _RB is significantly affected by voltage scan rate, range and direction, and illumination. The underlying mechanism is explained by drift-diffusion modeling taking into account the electric field generated by directional ion migration. The latter can hinder the movement of charge carriers and cause the observed variable V _RB and DRB behavior. Predictably, the understanding of the dynamic process is crucial to establish a standard V _RB measurement procedure and further promote the commercialization of PSCs.

By synthesizing a random terpolymer PBDB-TFCl and combining a ternary blending strategy, favorable phase separation and reinforced molecular packing are obtained. Resulting flexible organic solar modules exhibit maximum power conversion efficiency of 12.7% and excellent mechanical properties and photostability.

Abstract

All-polymer solar cells (all-PSCs) possess excellent operation stability and mechanical robustness than other types of organic solar cells, thereby attracting considerable attention for wearable flexible electron devices. However, the power conversion efficiencies (PCEs) of all-PSCs are still lagging behind those of small-molecule-acceptor-based systems owing to the limitation of photoactive materials and unsatisfactory blend morphology. In this work, a novel terpolymer, denoted as PBDB-TFCl (poly4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b″]dithiophene-1,3-bis(2-ethylhexyl)-5,7-di(thiophen-2-yl)-4H,8H-benzo[1,2-c:4,5-c″]dithiophene-4,8-dione-4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene), is used as an electron donor coupled with a ternary strategy to optimize the performance of all-PSCs. The addition of PBDB-TCl unit deepens the highest occupied molecular orbital energy level, reducing voltage losses. Moreover, the introduction of the guest donor (D18-Cl) effectively regulates the phase-transition kinetics of PBDB-TFCl:D18-Cl:PY-IT during the film formation, leading to ideal size of aggregations and enhanced crystallinity. PBDB-TFCl:D18-Cl:PY-IT devices exhibit a PCE of 18.6% (certified as 18.3%), judged as the highest value so far obtained with all-PSCs. Besides, based on the ternary active layer, the manufactured 36 cm² flexible modules exhibit a PCE of 15.1%. Meanwhile, the ternary PSCs exhibit superior photostability and mechanical stability. In summary, the proposed strategy, based on molecular design and the ternary strategy, allows optimization of the all-polymer blend morphology and improvement of the photovoltaic performance for stable large-scale flexible PSCs.

By regulating the sequence structure of conjugated block copolymers by two-pot polymerization, D18(40)-b-PYIT is obtained which enables single-component organic solar cells to achieve 13.4 % efficiency with enhanced stability. In addition, for the first time, large-area rigid and flexible single-component organic solar cells are reported with an impressive efficiency of 11.62 % and 10.73 %, respectively, much higher than their corresponding binary devices.

Abstract

Single-component organic solar cells (SCOSCs) based on conjugated block copolymers (CBCs) by covalently bonding a polymer donor and polymer acceptor become more and more appealing due to the formation of a favorable and stable morphology. Unfortunately, a deep understanding of the effect of the assembly behavior caused by the sequence structure of CBCs on the device performance is still missing. Herein, from the aspect of manipulating the sequence length and distribution regularity of CBCs, we synthesized a series of new CBCs, namely D18(20)-b-PYIT, D18(40)-b-PYIT and D18(60)-b-PYIT by two-pot polymerization, and D18(40)-b-PYIT(r) by traditional one-pot method. It is observed that precise manipulation of sequence length and distribution regularity of the polymer blocks fine-tunes the self-assembly of the CBCs, optimizes film morphology, improves optoelectronic properties, and reduces energy loss, leading to simultaneously improved efficiency and stability. Among these CBCs, the D18(40)-b-PYIT-based device achieves a high efficiency of 13.4 % with enhanced stability, which is an outstanding performance among SCOSCs. Importantly, the regular sequence distribution and suitable sequence length of the CBCs enable a facile film-forming process of the printed device. For the first time, the blade-coated large-area rigid/flexible SCOSCs are fabricated, delivering an impressive efficiency of 11.62 %/10.73 %, much higher than their corresponding binary devices.

Introduction of binary additives leads to 2D/3D perovskites with gradient phase distribution and favorable energy funnels, which were constructed to facilitate charge transfer across the devices. The 2D components serve as a “band-aid” to heal the defects and toughen the buried heterointerfaces, yielding an efficiency of 22.5 % for fast-annealed perovskite solar cells.

Abstract

The 2D/3D perovskite heterostructures have been widely investigated to enhance the efficiency and stability of perovskite solar cells (PSCs). However, rational manipulation of phase distribution and energy level alignment in such 2D/3D perovskite hybrids are still of great challenge. Herein, we successfully achieved spontaneous phase alignment of 2D/3D perovskite heterostructures by concurrently introducing both 2D perovskite component and organic halide additive. The graded phase distribution of 2D perovskites with different n values and 3D perovskites induced favorable energy band alignment across the perovskite film and boosted the charge transfer at the relevant heterointerfaces. Moreover, the 2D perovskite component also acted as a “band-aid” to simultaneously passivate the defects and release the residual tensile stress of perovskite films. Encouragingly, the blade-coated PSCs based on only ≈2 s in-situ fast annealed 2D/3D perovskite films with favorable energy funnels and toughened heterointerfaces achieved promising efficiencies of 22.5 %, accompanied by extended lifespan. To our knowledge, this is the highest reported efficiency for the PSCs fabricated with energy-saved thermal treatment just within a few seconds, which also outperformed those state-of-the-art annealing-free analogues. Such a two-second-in-situ-annealing technique could save the energy cost by up to 99.6 % during device fabrication, which will grant its low-coast implementation.

The transparent conductive oxide glass substrates are the most impacting component of perovskite solar cells (PSCs) from an environmental and economical perspective. It can be recycled by adopting healthy and environmentally safe solvent dimethyl sulfoxide, which allows the production of new generation PSCs that retain 100% of the original power conversion efficiency.

Abstract

Transparent conductive oxide (TCO)-coated glasses are the most expensive and environmentally impacting components of perovskite solar cells (PSCs), comprising 56% of the total cost of a perovskite module and 96% of its carbon footprint. Thus, recycling TCO glasses from end-of-life perovskite modules can reduce both their levelized cost of electricity and energy payback time. In this work, tin oxide (SnO₂)-coated indium tin oxide glasses are refurbished from n-i-p PSCs employing dimethyl sulfoxide as a green solvent to dissolve the upper layers of the devices. Employing the recovered substrates, new-generation PSCs are produced, which retain the same champion power conversion efficiency (PCE) of 22.6% as fresh samples and display an even higher average PCE. This performance enhancement is investigated through compositional and electrical analyses that demonstrate that the proposed recycling protocol induces beneficial surface modifications on the SnO₂/perovskite interface and trap passivation, boosting charge extraction.

A multi-fluorine-containing higher fullerene-porphyrin dyad (F₇₀PD) is synthesized and applied to regulate the crystal orientation and the buried interface defects of the perovskite film. The robust interface engineering not only reduces the non-radiative recombination in bulk and interface of the perovskite layer but also increases the activation energy of ion migration, enabling efficient and stable perovskite solar cells.

Abstract

Perovskite films prepared by the solution process usually result in irregular grain orientation and rich buried interface defects, hindering the further improvement of device performance. Herein, multi-fluorine-containing C₆₀- and C₇₀ (higher fullerene)-porphyrin derivatives, F₆₀PD and F₇₀PD, are synthesized and pre-buried to modify the SnO₂/perovskite heterointerface. The F₇₀PD modification layer provides a better perovskite quality and more effective electron transporting capability compared to the corresponding F₆₀PD, with the F₇₀PD being more effective in regulating the perovskite growth, passivating the buried interface defects, and optimizing the interface energy level alignment. Consequently, the F₇₀PD-based device delivers superior efficiency and stability than the control and F₆₀PD-based devices. The F₇₀PD-based device yields a champion efficiency of 24.09% with negligible hysteresis. Meanwhile, due to the increased activation energy of ion migration, the F₇₀PD-based device maintains 80% of its initial efficiency after operating at the maximum power point for 1620 h. This study highlights the potential of designing higher fullerene materials for buried interface to further improve the perovskite solar cells’ performance.