Search

Numerous deep/shallow level defects generated at the surface/grain boundaries of perovskite during uncontrollable crystallization pose a formidable challenge to the photovoltaic performance of perovskite solar cells (PSCs). Herein, an organometallic cobaltocenium salt additive, 1‐propanol‐2‐(1,2,3‐triazol‐4‐yl) cobaltocenium hexafluorophosphate (PTCoPF6), is incorporated into the perovskite precursor solution to regulate crystallization and minimize holistic defects for high‐performance inverted PSCs. The cobaltocenium cations and PF6− in PTCoPF6 stabilize the Pb‐I framework and repair the shallow‐level defects of positively and negatively charged vacancies in the perovskite. The N═N in the triazole ring of PTCoPF6 can passivate the deep‐level defects of uncoordinated lead. The interaction between PTCoPF6 and perovskite materials delays perovskite nucleation and crystal growth, ensuring high‐quality perovskite with large grains, and suppressing non‐radiative recombination and ion migration. Therefore, the PTCoPF6‐incorporated PSC achieves an impressive power conversion efficiency of 25.03% and outstanding long‐term stability. Unencapsulated and encapsulated PTCoPF6‐incorporated PSCs maintain 93% and 95% of their initial efficiencies under 85 °C storage in a nitrogen atmosphere for 1000 h and maximum power point tracking for nearly 1000 h, respectively. Synergistic crystallization kinetic modulation and deep/shallow level defect passivation with ionized metal‐organic complex additives will become prevalent methods to improve the efficiency and stability of PSCs. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Encapsulation engineering is an effective strategy to improve the stability of perovskite solar cells. However, current encapsulation materials are not suitable for lead-based devices because of their complex encapsulation processes, poor thermal management, and inefficient lead leakage suppression. In this work, we design a self-crosslinked fluorosilicone polymer gel, achieving nondestructive encapsulation at room temperature. Moreover, the proposed encapsulation strategy effectively promotes heat transfer and mitigates the potential impact of heat accumulation. As a result, the encapsulated devices maintain 98% of the normalized power conversion efficiency after 1000 h in the damp heat test and retain 95% of the normalized efficiency after 220 cycles in the thermal cycling test, satisfying the requirements of the International Electrotechnical Commission 61215 standard. The encapsulated devices also exhibit excellent lead leakage inhibition rates, 99% in the rain test and 98% in the immersion test, owing to excellent glass protection and strong coordination interaction. Our strategy provides a universal and integrated solution for achieving efficient, stable, and sustainable perovskite photovoltaics. Encapsulation engineering is an effective strategy to improve the stability of perovskite solar cells. Here, authors design and synthesize self-crosslinked fluorosilicone polymer gel for nondestructive encapsulation at room temperature, and maintain 98% of efficiency after 1000 h in damp heat test. [ABSTRACT FROM AUTHOR]

Because of the compatibility with tandem devices and the ability to be manufactured at low temperatures, inverted perovskite solar cells have generated far‐ranging interest for potential commercial applications. However, their efficiency remains inadequate owing to various traps in the perovskite film and the restricted hole blocking ability of the electron transport layer. Thus, in this work, a wide‐bandgap n‐type semiconductor, 4,6‐bis(3,5‐di(pyridin‐4‐yl)phenyl)‐2‐phenylpyrimidine (B4PyPPM), to modify a perovskite film via an anti‐solvent method is introduced. The nitrogen sites of pyrimidine and pyridine rings in B4PyPPM exhibit strong interactions with the undercoordinated lead ions in the perovskite material. These interactions can reduce the trap state densities and inhibit nonradiative recombination of the perovskite bulk. Moreover, B4PyPPM can partially aggregate on the perovskite surface, leading to an improvement in the hole‐blocking ability at its interface. This modification can also increase the built‐in potential and upshift the Fermi level of the modified perovskite film, promoting electron extraction to the electron transport layer. The champion device achieves a high efficiency of 23.51%. Meantime, the sealed device retains ≈80% of its initial performance under a maximum power point tracking for nearly 2400 h, demonstrating an excellent operational stability. [ABSTRACT FROM AUTHOR]

Nickel oxide (NiOx) is a promising hole transport material in inverted organic‐inorganic metal halide perovskite solar cells. However, its low intrinsic conductivity hinders its further improvement in device performance. Here, we employ a trimercapto‐s‐triazine trisodium salt (TTTS) as a chelating agent of Ni2+ in the NiOx layer to improve its conductivity. Due to the electron‐deficient triazine ring, the TTTS complexes with Ni2+ in NiOx via a strong Ni2+‐N coordination bond and increases the ratio of Ni3+:Ni2+. The increased Ni3+ concentration adjusts the band structure of NiOx, thus enhancing hole density and mobility, eventually improving the intrinsic conductivity of NiOx. As a result, the device with TTTS modification displays a champion power conversion efficiency (PCE) of 22.81%. The encapsulated device based on a modified‐NiOx layer maintains 94% of its initial power output at the maximum power point and continuous one‐sun illumination for 1000 h at 45 °C. In addition, the unencapsulated target devices also maintain 92% at 60 ± 5% relative humidity and 25 °C in the air for 5000 h; and 91% at 85 °C in a nitrogen atmosphere for 1000 h. The research provides an effective strategy to enhance PCE and stability of inverted PSCs via modifying NiOx films with triazine molecule. [ABSTRACT FROM AUTHOR]

Although perovskite solar cells (PSCs) are on the road to industrialization, the operational stability under high efficiency still needs to be improved, and the water solubility of lead ions (Pb2+) will cause environmental pollution problems. Herein, it is successfully implanted an environment‐friendly (biodegradability) poly(butylene adipate‐coterephthalate) polymer (PBAT) into the perovskite film, which can passivate the uncoordinated Pb2+ and neutral iodine defects of the perovskite material because of the adequate carbonyl groups and benzene rings in PBAT polymer, thereby regulating the crystallization of perovskite film with lower trap density, inhibiting the nonradiative recombination and improving charge carrier transport. As a result, the polymer‐incorporated inverted PSCs achieve optimal conversion efficiencies of 22.07% (0.1 cm2) and 20.31% (1 cm2). Meanwhile, the incorporated device, after being encapsulated, exhibits a prominent improvement in operational stability of high‐efficiency device under maximum power point tracking and continuous one sunlight illumination, maintaining the initial efficiency of 80% for 3249 h. More importantly, the polymer network can protect Pb2+ from being dissolved by water and prevent nearly 98% of Pb2+ from leaking by directly immersing the polymer‐coated perovskite film in water. Environmental‐friendly molecules provide new hope for solving lead poisoning and improving device operational stability under high efficiency. [ABSTRACT FROM AUTHOR]

The harmful defects accumulated at surfaces and grain boundaries (GBs) limit the performance and stability of perovskite solar cells (PSCs), which results from the poor crystallization and ion migration. Here, a multifunctional molecular additive L‐4‐fluorophenylalanine (FPA) is explored for highly efficient and stable inverted PSCs. The multifunction is realized through comprehensive defect passivation, surface hydrophobicity, and crystallization control with the multitude groups, such as the amino and carbonyl groups for passivating the unsaturated lead defects at GBs, and the benzene ring for electron‐deficient iodine defects, and the fluorine group for the improvement of crystallization and the inhibition of ions migration. The resulting inverted device shows a champion power conversion efficiency of 21.28% with negligible hysteresis. The unencapsulated FPA‐modified devices maintain nearly 90% of the initial performance after high‐temperature (85 °C) thermal accelerated aging for 500 h and 85% after aging for 4000 h under ambient conditions, and about 90% of the original efficiency after being maximum power point tracked for 1000 h under continuous illumination. This study provides a multipronged strategy to the future design of PSCs with higher efficiency and enhanced stability. [ABSTRACT FROM AUTHOR]

The electron transport layer (ETL) is one of the determinants for the performance improvement of perovskite solar cells (PSCs). Here, a multifunctional molecule named 4‐fluoro‐phenylalanine (4‐F‐Phe) to modify the surface of tin oxide (SnO2) ETL is introduced as a novel interfacial layer for high‐efficiency PSCs. The modified SnO2 ETLs exhibit an elevated Fermi level, increasing the carrier extraction and suppressing the interfacial recombination. In addition, the various functional groups of the 4‐F‐Phe realize strong interfacial interactions with both the bottom SnO2 ETLs and the top perovskite, which reduces trap state density significantly to promote the interfacial charge transport. As a result, power conversion efficiency (PCE) for the 4‐F‐Phe optimized device reaches 21.91%. Most importantly, the 4‐F‐Phe optimized device without encapsulation maintains 91% of its initial PCE after 2000 h at 25 °C with a humidity of 50 ± 5%, and 90% of the initial PCE after 1000 h at 80 °C in N2. In addition, the encapsulated devices maintain 94% of their initial efficiency under continuous 1 sun illumination for 1000 h when tracking the maximum power point at 45 °C. This work provides a new strategy of modifying ETL to simultaneously improve the efficiency and stability of PSCs. [ABSTRACT FROM AUTHOR]

The performance enhancement of inverted perovskite solar cells applying nickel oxide (NiOx) as the hole transport layer (HTL) has been limited by impurity ions (such as nitrate ions). Herein, we have proposed a strategy to obtain high‐quality NiOx nanoparticles via an ionic liquid‐assisted synthesis method (NiOx‐IL). Experimental and theoretical results illustrate that the cation of the ionic liquid can inhibit the adsorption of impurity ions on nickel hydroxide through a strong hydrogen bond and low adsorption energy, thereby obtaining NiOx‐IL HTL with high conductivity and strong hole‐extraction ability. Importantly, the removal of impurity ions can effectively suppress the redox reaction between the NiOx film and the perovskite film, thus slowing down the deterioration of device performance. Consequently, the modified inverted device shows a striking efficiency exceeding 22.62 %, and superior stability maintaining 92 % efficiency at a maximum power point tracking under one sun illumination for 1000 h. [ABSTRACT FROM AUTHOR]

A series of new push-pull organic dyes ( BT-I- VI), incorporating electron-withdrawing bithiazole with a thiophene, furan, benzene, or cyano moiety, as π spacer have been synthesized, characterized, and used as the sensitizers for dye-sensitized solar cells (DSSCs). In comparison with the model compound T1, these dyes containing a thiophene moiety between triphenylamine and bithiazole display enhanced spectral responses in the red portion of the solar spectrum. Electrochemical measurement data indicate that the HOMO and LUMO energy levels can be tuned by introducing different π spacers between the bithiazole moiety and cyanoacrylic acid acceptor. The incorporation of bithiazole substituted with two hexyl groups is highly beneficial to prevent close π-π aggregation, thus favorably suppressing charge recombination and intermolecular interaction. The overall conversion efficiencies of DSSCs based on bithiazole dyes are in the range of 3.58 to 7.51 %, in which BT-I-based DSSCs showed the best photovoltaic performance: a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 81.1 %, a short-circuit photocurrent density ( Jsc) of 15.69 mA cm−2, an open-circuit photovoltage ( Voc) of 778 mV, and a fill factor (ff) of 0.61, which correspond to an overall conversion efficiency of 7.51 % under standard global AM 1.5 solar light conditions. Most importantly, long-term stability of the BT-I- III-based DSSCs with ionic-liquid electrolytes under 1000 h of light soaking was demonstrated and BT-II with a furan moiety exhibited better photovoltaic performance of up to 5.75 % power conversion efficiency. [ABSTRACT FROM AUTHOR]

Tin oxide (SnO2) has recently received increasing attention as an electron transport layer (ETL) in planar perovskite solar cells (PSCs) and is considered a possible alternative to titanium oxide (TiO2). However, planar devices based on pure solution‐processed SnO2 ETL still have hysteresis, which greatly limits the application of SnO2 in high‐efficiency solar cells. Herein, to address this issue, a hybrid ETL of SnO2 and carbon nanotubes (CNTs) is fabricated by a simple thermal decomposing of a mixed solution of SnCl4·5H2O and pretreated CNTs (termed SnO2–CNT). The addition of CNTs can significantly improve the conductivity of SnO2 films and reduce the trap‐state density of SnO2 films, which benefit carrier transfer from the perovskite layer to the cathode. As a result, a high efficiency of 20.33% is achieved in the hysteresis‐free PSCs based on SnO2–CNT ETL, which shows 13.58% enhancement compared with the conventional device (power conversion efficiency = 17.90%). [ABSTRACT FROM AUTHOR]

Solution‐processed Sb2S3 planar heterojunction solar cells have shown great progress in power conversion efficiency (PCE) in recent years. However, a conventional solution process yields Sb2S3 films with a small grain size. Herein, an alcohol vapor post‐annealing strategy is reported that uses alcohol vapors to facilitate grain growth of Sb2S3 films during annealing, achieving films with a larger grain size and better crystallinity. A series of alcohols with different polarities are used for the vapor post‐annealing. Methanol with the highest polarity provides films with the largest grain size. As a result, the Sb2S3 films prepared via vapor post‐annealing show enhanced light absorption, longer carrier lifetime, and less carrier recombination, which are verified by photoluminescence, transient photovoltage, suns‐short‐circuit photocurrent density, and suns‐open‐circuit voltage measurements. The Sb2S3 solar cells post‐annealed with methanol vapor exhibit a PCE of 5.27%, showing a drastic improvement of 31% compared with the non‐treated devices. The alcohol vapor post‐annealing approach presents a new avenue toward controlling the morphology and crystallinity of solution‐processed Sb2S3 films and achieving efficient Sb2S3 solar cells. [ABSTRACT FROM AUTHOR]

• Urea-complexed SnO 2 is designed by a low temperature solution-processed method. • The amino groups on urea improve the electrical performance of SnO 2. • The amino groups also passivate the surface trap states of upper perovskite films. • A high-power conversion efficiency of 20.25% is obtained. SnO 2 is regarded as the most promising electron transporting layer (ETL) material for perovskite solar cells (PSCs). Various functional groups are introduced onto the SnO 2 surface by interface modification with the purpose of improving the performance of the PSCs. However, most of the modifications are achieved in two-step approach, which are complicated and not easily realized. Here, we employ a facile one-step, low-temperature, and effective method to synthesis urea-complexed SnO 2 ETL (referred as Urea-SnO 2). The –NH 2 groups on Urea-SnO 2 attributes to facilitate the charge transfer within the SnO 2 ETL and reduce trap state density in the perovskite film through the chemical interactions. Therefore, The PSCs based on the Urea-SnO 2 ETL exhibit a champion power conversion efficiency (PCE) of 20.25%, which is more excellent than the devices based on the pristine SnO 2 ETL (17.60%). Functionalization of SnO 2 in situ by the precursor solution method offers an efficient method for high performance planar PSCs. [ABSTRACT FROM AUTHOR]