Chen Weijie

Influence of spatial symmetry on device performance is investigated by using molecules based on symmetrical bis(2-chloroethyl)ammonium cation (B(CE)A⁺) and asymmetrical 2-chloroethylammonium cation (CEA⁺) as interface layers between the perovskite and spiro-OMeTAD. The symmetrical B(CE)A⁺ cations lead to a more homogeneous surface potential and comprehensive chelation compared to the asymmetrical CEA⁺ cations. This strategy achieves a remarkable efficiency of 25.60%.

Abstract

Modifying perovskite surface using various organic ammonium halide cations has proven to be an effective approach for enhancing the overall performance of perovskite solar cells. Nevertheless, the impact of the structural symmetry of these ammonium halide cations on perovskite interface termination has remained uncertain. Here, this work investigates the influence of symmetry on the performance of the devices, using molecules based on symmetrical bis(2-chloroethyl)ammonium cation (B(CE)A⁺) and asymmetrical 2-chloroethylammonium cation (CEA⁺) as interface layers between the perovskite and hole transport layer. These results reveal that the symmetrical B(CE)A⁺ cations lead to a more homogeneous surface potential and more comprehensive chelation with uncoordinated Pb²⁺ compared to the asymmetrical cations, resulting in a more favorable energy band alignment and strengthened defect healing. This strategy, leveraging the spatial geometrical symmetry of the interface cations, promotes hole carrier extraction between functional layers and reduces nonradiative recombination on the perovskite surface. Consequently, perovskite solar cells processed with the symmetrical B(CE)A⁺ cations achieve a power conversion efficiency (PCE) of 25.60% and retain ≈91% of their initial PCE after 500 h of maximum power point operation. This work highlights the significant benefits of utilizing structurally symmetrical cations in promoting the performance and stability of perovskite solar cells.

Asymmetric halogenation strategy (AHS) can enhance dipole moment and induce more positive surface electrostatic potential, contributing to the compact and diverse molecular stacking, thus promoting exciton delocalization for efficient charge generation. Besides, AHS suppresses electron-phonon coupling, resulting in reduced nonradiative recombination loss and enabling PTQ10 : HCl-BTA33 to yield the highest PCE of 12.54 % with a V _oc of 1.201 V.

Abstract

High open-circuit voltage (V _oc) organic solar cells (OSCs) have received increasing attention because of their promising application in tandem devices and indoor photovoltaics. However, the lack of a precise correlation between molecular structure and stacking behaviors of wide band gap electron acceptors has greatly limited its development. Here, we adopted an asymmetric halogenation strategy (AHS) and synthesized two completely non-fused ring electron acceptors (NFREAs), HF-BTA33 and HCl-BTA33. The results show that AHS significantly enhances the molecular dipoles and suppresses electron-phonon coupling, resulting in enhanced intramolecular/intermolecular interactions and decreased nonradiative decay. As a result, PTQ10 : HF-BTA33 realizes a power conversion efficiency (PCE) of 11.42 % with a V _oc of 1.232 V, higher than that of symmetric analogue F-BTA33 (PCE=10.02 %, V _oc=1.197 V). Notably, PTQ10 : HCl-BTA33 achieves the highest PCE of 12.54 % with a V _oc of 1.201 V due to the long-range ordered π–π packing and enhanced surface electrostatic interactions thereby facilitating exciton dissociation and charge transport. This work not only proves that asymmetric halogenation of completely NFREAs is a simple and effective strategy for achieving both high PCE and V _oc, but also provides deeper insights for the precise molecular design of low cost completely NFREAs.

An incorporation strategy of using small-size A-site and large-size X-site to modulate the lattice distortion and improve the film quality of Wide-bandgap (WBG) formamidinium-methylammonium (FAMA) perovskite films for photostable perovskite solar cells (PSCs) based on two-step deposition method. Leading to the suppression of photoinduced phase segregation in the resultant RbCsFAMA quadruple cation perovskites.

Abstract

Wide-bandgap (WBG) perovskite solar cells (PSCs) have been widely used as the top cell of tandem solar cells. However, photoinduced phase segregation and high open-circuit voltage loss pose significant obstacles to the development of WBG PSCs. Here, a two-step small-size A-site and large-size X-site incorporation strategy is reported to modulate the lattice distortion and improve the film quality of WBG formamidinium-methylammonium (FAMA) perovskite films for photostable PSCs based on two-step deposition method. First, CsI with content of 0–20% is introduced to tune the lattice distortion and film quality of FAMA perovskite with a bandgap of 1.70 eV. Then, 4% RbI is incorporated to further modulate the perovskite growth and lattice distortion, leading to the suppression of photoinduced phase segregation in the resultant RbCsFAMA quadruple cation perovskites. As a result, the 20%CsI/4%RbI-doped device obtains a promising efficiency of 20.6%, and the corresponding perovskite film shows good photothermal stability. Even without encapsulation, the device can maintain 92% of its initial efficiency after 1000 h of continuous operation under 1 sun equivalent white light-emitting diode illumination.

Bulk-heterojunction is buried into layer-by-layer structures to realize decent vertical phase distribution and sufficient exciton dissociation interfaces simultaneously. This scheme possesses efficient exciton dissociation and rapid charge transport, resulting in a power conversion efficiency of 16.0% in organic solar cells with 500-nm-thick active layers.

Abstract

Large-area printing fabrication is a distinctive feature of organic solar cells (OSCs). However, the advance of upscalable fabrication is challenged by the thickness of organic active layers considering the importance of both exciton dissociation and charge collection. In this work, a bulk-heterojunction-buried (buried-BHJ) structure is introduced by sequential deposition to realize efficient exciton dissociation and charge collection, thereby contributing to efficient OSCs with 500 nm thick active layers. The buried-BHJ distributes donor and acceptor phases in the vertical direction as charge transport channels, while numerous BHJ interfaces are buried in each phase to facilitate exciton dissociation simultaneously. It is found that buried-BHJ configurations possess efficient exciton dissociation and rapid charge transport, resulting in reduced recombination losses. In comparison with traditional structures, the buried-BHJ structure displays a decent tolerance to film thickness. In particular, a power conversion efficiency of 16.0% is achieved with active layers at a thickness of 500 nm. To the best of the authors’ knowledge, this represents the champion efficiency of thick film OSCs.

Publication date: 1 June 2024

Source: Nano Energy, Volume 124

Author(s): Fuhua Hou, Xiaoqi Ren, Haikuo Guo, Xuli Ning, Yulong Wang, Tiantian Li, Chengjun Zhu, Ying Zhao, Xiaodan Zhang

Publication date: 19 June 2024

Source: Joule, Volume 8, Issue 6

Author(s): Junjie Zhou, Liguo Tan, Yue Liu, Hang Li, Xiaopeng Liu, Minghao Li, Siyang Wang, Yu Zhang, Chaofan Jiang, Ruimao Hua, Wolfgang Tress, Simone Meloni, Chenyi Yi

In this work, Ag and Cu films are successfully transferred from PTFE onto PSCs as top electrodes. Further, the energy-level matching between HTL and metal electrodes is improved by doping regulation. Thus obtained transfer Ag and Cu electrode perovskite devices reach efficiencies of 18.41% and 17.25%, respectively, comparable to those of evaporated electrode devices.

As an alternative technology to the standard evaporated metal top electrode in perovskite solar cells, the transfer method top electrode is featured with low cost, simple process, and ease of scalability. However, as the transfer method preparation of the less expensive metal electrodes (Ag and Cu) is explored, the mismatch between the hole-transport layer and the top electrode results in anomalous photovoltaic properties. In this study, the work function of the hole-transporting material is adjusted by changing the dopant content to achieve a good energy-level match with either Ag or Cu electrode material. The power conversion efficiencies of perovskite devices based on transferred Ag and Cu electrodes can reach 18.41% and 17.25%, respectively, which are comparable to the performance of the evaporated top electrode devices.

A new green-emitting material ((CH₃)₄ N)₂(C₂H₅)₄N·MnBr₄ is synthesized and introduced on the perovskite layer to achieve both defect passivation and light complementation. The green luminescence of this single crystal at the interface is found to provide secondary light absorption, and it is also found that the excess PbI₂ on the surface of perovskite can be effectively removed.

In conventional p–i–n inverted perovskite solar cells (PSCs), there exists considerable energy loss due to both unsatisfactory light path design and trap-induced interfacial defects. The sunlight is absorbed competitively by conductive oxide substrates and hole transport material in front of the perovskite layer, while the opaque metal back electrode also prevents light penetration. Worse yet, there is severe nonradiative charge recombination caused by defects between the perovskite layer and the electron transport material. To tackle the above two issues, a new green-emitting material ((CH₃)₄ N)₂(C₂H₅)₄N·MnBr₄ is synthesized and introduced in/on the perovskite layer to achieve both defect passivation and light complementation. The green luminescence of this single crystal at the interface is found to provide secondary light absorption, as evidenced by a remarkable promotion of short-circuit current density. It is also found that the excess PbI₂ on the surface of perovskite can be effectively removed, and as the interfacial additive, ((CH₃)₄ N)₂(C₂H₅)₄ N·MnBr₄ inhibits trap-assisted recombination losses, which provides favorable energy-level alignment and extends charge carrier lifetime. As a result, the champion PCE (21.23%) of the target-treated ((CH₃)₄ N)₂(C₂H₅)₄ N·MnBr₄ device exceeds that 19.5% of the pristine-without ((CH₃)₄ N)₂(C₂H₅)₄ N·MnBr₄ device. This work provides an effective interfacial strategy for high-performance and stable inverted PSCs.

Gold (Au) penetration into the perovskite light absorber during vacuum deposition of the Au electrode on top of 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobi-fluorene (spiro-OMeTAD) hole transport layer induces detrimental carrier recombination. Inserting the molybdenum oxide interlayer between the spiro-OMeTAD layer and the Au electrode reduces the amount of the penetrated Au component, increasing PCEs from ≈16.9% to ≈19.6%.

Perovskite solar cells (PSCs) have undergone an unprecedentedly rapid development in both power conversion efficiency (PCE) and operational durability. However, a number of unknown challenges remain before PSC products are ready to launch. Herein, it is demonstrated that the vacuum deposition of gold (Au) onto the organic hole-transport layer (HTL) results in Au penetration into the perovskite layer. This Au penetration proves to be a limiting factor in PCE due to detrimental carrier recombination caused by the penetrated Au component inside the perovskite light absorber. To mitigate this issue, a thin molybdenum oxide (MoO _x ) interlayer between the organic HTL and the Au electrode is introduced, effectively reducing the Au penetration and suppressing the carrier recombination. Consequently, this MoO _x introduction increases PCEs from ≈16.9% to ≈19.6% by ≈2.7%. Furthermore, using the MoO _x interlayer improves the long-term durability of PSCs. These findings are crucial in elucidating a basic mechanism that limits PCE and in advancing the fabrication of PSC products with even higher performance.

Herein, the effect of mixed self-assembled hole-transport monolayers, which blend [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid and [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid, on the efficiency and stability of perovskite solar cells (PSCs) is investigated. It is found that mixed self-assembled monolayer (SAM) enables simultaneous improvement of efficiency and stability of PSCs. These findings suggest the potential of mixed SAM approaches for the realization of high-performance PSCs.

As one of the interface engineering methods for realizing high-performance perovskite solar cells (PSCs), self-assembled monolayers (SAMs) with hole-transport properties have recently been applied as an effective way to reduce energy losses at the hole-transport layer/perovskite interface, especially in PSCs with p–i–n structure. However, there are still limitations in implementing PSC with high efficiency and high stability due to the inherent weaknesses of single SAMs. Herein, it is demonstrated that a mixed self-assembled hole-transport monolayer with an appropriate mixture of [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) and [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) enables simultaneous improvement of efficiency and stability of PSCs. In the mixed SAM, MeO-2PACz maintains favorable wettability to produce high-quality films, while the deep highest occupied molecular orbital of Me-4PACz optimizes the energy level for efficient charge transfer, resulting in improved PSC performance. Encouragingly, Me-4PACz mitigates the stability issues of MeO-2PACz, producing mixed SAM-based PSCs with excellent stability. These PSCs achieve up to 20.63% efficiency and exhibit excellent thermal long-term stability, retaining 90% and 80% of their initial efficiency after approximately 1400 and 2100 h at 65 °C in an N₂ atmosphere. These findings suggest the potential of mixed SAM approaches for the realization of high-performance PSCs.

A review of the optimization process of four-terminal and two-terminal perovskite/copper indium gallium selenide (CIGS) tandem solar cells (TSCs), including a summary of the key technologies and challenge in the material, structure, and optoelectronic properties of tandem cells, aiming to provide a comprehensive understanding of perovskite/CIGS TSCs and create ideas for their future development, is provided.

In recent years, perovskite solar cells (PSCs) have emerged as a focal point for numerous researchers due to their excellent photoelectric performance. In comparison to their single-junction devices, double-junction cells have exhibited the potential for superior power conversion efficiency (PCE). Copper indium gallium selenide (CIGS) solar cells, a well-established photovoltaic technology, can be used as a viable bottom cell candidate for double-junction tandem solar cells (TSCs). Recently, the PCE of the most advanced 4T perovskite/CIGS TSCs reached 29.9%, while the highest PCE of 2T perovskite/CIGS TSC is 24.2%, which develops relatively slowly. In contrast to the leading perovskite/silicon (Si) TSCs in terms of PCE (PCE_2T = 33.9%, PCE_4T = 30.35%), perovskite/CIGS TSCs exhibit distinctive advantages such as adjustable bandgap, high absorption coefficient, radiation resistance, and can be prepared on flexible substrates. Building upon these advantages, the optimization process in four-terminal and two-terminal perovskite/CIGS TSCs is elucidated, the key technologies and challenges in material, structure, and photoelectric performance of the tandem cells are summarized, and a prospective analysis of their future overall development in this review is provided. Furthermore, it is hoped to give readers a comprehensive understanding of perovskite/CIGS TSCs.

In this study, a room-temperature spin-coated IL, n-butylamine acetate (BAAc), is identified as an ideal passivation agent for formamidinium lead iodide (FAPbI₃) films. The PCE of the devices treated by BAAc RT achieves 24.76%, with a Voc value reaching as high as 1.19 V.

Abstract

Ionic liquid salts (ILs) are generally recognized as additives in perovskite precursor solutions to enhance the efficiency and stability of solar cells. However, the success of ILs incorporation as additives is highly dependent on the precursor formulation and perovskite crystallization process, posing challenges for industrial-scale implementation. In this study, a room-temperature spin-coated IL, n-butylamine acetate (BAAc), is identified as an ideal passivation agent for formamidinium lead iodide (FAPbI₃) films. Compared with other passivation methods, the room-temperature BAAc capping layer (BAAc RT) demonstrates more uniform and thorough passivation of surface defects in the FAPbI₃ perovskite. Additionally, it provides better energy level alignment for hole extraction. As a result, the champion n–i–p perovskite solar cell with a BAAc capping layer exhibits a power conversion efficiency (PCE) of 24.76%, with an open-circuit voltage (Voc) of 1.19 V, and a Voc loss of ≈330 mV. The PCE of the perovskite mini-module with BAAc RT reaches 20.47%, showcasing the effectiveness and viability of this method for manufacturing large-area perovskite solar cells. Moreover, the BAAc passivation layer also improves the long-term stability of unencapsulated FAPbI₃ perovskite solar cells, enabling a T80 lifetime of  3500 h when stored at 35% relative humidity at room temperature in an air atmosphere.

Two cost-effective fully non-fused ring electron acceptors BTZT-2Cl and BTZT-4Cl are developed and synthesized. A binary device based on D18:BTZT-4Cl gives a high power conversion efficiency (PCE) of 14.12%. The PCE is further improved to 15.41% using a ternary device by incorporating a good solubility and high compatibility BTZT-2Cl as the third component, which is one of highest efficiencies with V _oc exceeding 0.95 V for non-fused ring-based OPV to date.

Abstract

Simple chemical structure and simplified synthesis process of active layer materials are critical for advancing the practical application of organic solar cells. Herin, two completely non-fused ring electron acceptors BTZT-2Cl and BTZT-4Cl are developed. BTZT-4Cl exhibits an enhanced absorption band, increases electrostatic potential differences with D18, and improves crystallinity and molecular packing properties. Consequently, the binary device based on BTZT-4Cl displays a markedly improved efficiency of 14.12%, compared to the BTZT-2Cl-based device, which only achieves a moderate efficiency of 11.25%. More importantly, an alloy-like structure can be formed by incorporating a small amount of high miscibility and compatibility BTZT-2Cl. The ternary blend exhibits more compact molecular packing, efficient exciton dissociation, and an extended charge carrier lifetime due to the formation of an alloy-like structure. The ternary device achieves a decent efficiency of 15.41% with superior thermal stability and a high T ₈₀ lifetime over 1600 h after being aged at 65 °C. These results establish it as the most efficient among devices based on completely non-fused ring acceptors with both high efficiency and voltage. This study demonstrates a simple material design strategy and high-performance device optimization techniques, which are critical for advancing practical applications in the OSC field.

Publication date: July 2024

Source: Journal of Energy Chemistry, Volume 94

Author(s): Tian Chen, Ying Yang, Congtan Zhu, Weihuang Lin, Qilin Dai, Xueyi Guo

2-pyrrolidin-1-ium-1-ethylammonium tetrafluoroborate (PyE(BF₄)₂ can form hydrogen bonds and strong ionic interactions to stabilize the [PbI₆]⁴⁻ framework of perovskite, resulting in highly efficient perovskite solar cells with a notable power conversion efficiency of 23.80% and remarkable stability exceeding 1300 h under standard testing protocols (ISOS-V-1) .

In the rapidly developing field of photovoltaics, organic–inorganic metal halide perovskites are outstanding for their exceptional power conversion efficiencies (PCE), exceeding 26%. However, the full potential of these materials is often undermined by the prevalence of defects within their structure and at the grain surfaces, leading to significant nonradiative recombination losses. To meet this critical challenge, this study introduces a novel strategy involving a pyrrolidinium derivative and tetrafluoroborate ionic liquid, specifically 2-pyrrolidin-1-ium-1-ethylammonium tetrafluoroborate (PyE(BF₄)₂), as an additive in the perovskite precursor. This approach aims to meticulously control crystallization processes and effectively passivate defects on the surface and grain boundaries of the perovskite. The formation of N─H…I⁻ hydrogen bonds and strong ionic interactions, PyE(BF₄)₂ not only stabilizes the [PbI₆]⁴⁻ framework but also optimizes the valence band alignment with the hole transport layer. Empirical results demonstrate that perovskite solar cells modified with PyE(BF₄)₂ have achieved a notable PCE of 23.80% and remarkable stability exceeding 1300 h under standard testing protocols (ISOS-V-1). The findings emphasize the transformative potential of multifunctional ionic liquids in enhancing the performance and durability of perovskite-based photovoltaic devices, marking a significant step forward in pursuing sustainable and efficient solar energy solutions.

The additive with the best-matched molecular size for selected perovskite exhibits the most effective passivation effect, while the additives with the mismatched size have a negative effect on the device performance simply because of the size difference.

Abstract

Surface engineering in perovskite solar cells, especially for the upper surface of perovskite, is widely studied. However, most of these studies have primarily focused on the interaction between additive functional groups and perovskite point defects, neglecting the influence of other parts of additive molecules. Herein, additives with -NH₃ ⁺ functional group are introduced at the perovskite surface to suppress surface defects. The chain lengths of these additives vary to conduct a detailed investigation into the impact of molecular size. The results indicate that the propane-1,3-diamine dihydroiodide (PDAI₂), which possesses the most suitable size, exhibited obvious optimization effects. Whereas the molecules, methylenediamine dihydroiodide (MDAI₂) and pentane-1,5-diamine dihydroiodide (PentDAI₂) with unsuitable size, lead to a deterioration in device performance. The PDAI₂-treated devices achieved a certified power conversion efficiency (PCE) of 25.81% and the unencapsulated devices retained over 80% of their initial PCE after 600 h AM1.5 illumination.

A benzylamine-based spacer, namely 3,5-difluorobenzylamine (DF-BZA), is developed for stable and efficient quasi-2D-RP perovskite solar cells (PSCs). Due to the high electron negativity of F atoms, DF-BZA has a higher dipole (12.48 D) than BZA (8.90 D), which is positive to increase the dielectric constant of DF-BZA-based 2D perovskite, resulting in reduced exciton binding energy. As a result, the optimized (DF-BZA)₂FA₃Pb₄I₁₃ PSCs achieved a power conversion efficiency (PCE) of 19.24%. This represents the champion PCE using FA as the A-site cation in quasi-2D RPPs with n = 4.

Abstract

2D Ruddlesden–Popper perovskites (RPP) with excellent environmental and structural stability are emerging photovoltaic materials. Here, a benzylamine-based spacer, namely 3,5-difluorobenzylamine (DF-BZA), is developed for stable and efficient quasi-2D-RP perovskite solar cells (PSCs). Compared to benzylamine (BZA)-based quasi-2D RPP, the DF-BZA-based perovskite film exhibited superior film quality with significantly enlarged grain size and improved charge carrier lifetime owing to the fluorine atoms in DF-BZA. As a result, the optimized (DF-BZA)₂FA₃Pb₄I₁₃ PSCs achieve a power conversion efficiency (PCE) of 19.24%, while BZA-based PSCs ((BZA)₂FA₃Pb₄I₁₃) only achieve a PCE of 17.04%. This represents the champion PCE using FA as the A-site cation in quasi-2D RPPs with n = 4. Moreover, due to the effective insertion of fluorinated spacers into the inorganic layers, the moisture resistance stability and 85 °C thermal stability of (DF-BZA)₂FA₃Pb₄I₁₃ are significantly improved. The improvement of photovoltaic performance and stability highlight the great potential of DF-BZA-based spacer for high-performance quasi-2D RP PSCs.

Steric hindrance increase in outer alkyl chain of Se-containing acceptors causes the stacking pattern of two molecules in one dimer to shift. Se-EH with a slower crystallinity formed a suitable domain size and a favorable interpenetrating nanofiber network, reducing sub-ns recombination rate to promote balanced transport of carriers, helping improve the fill factor of Se-containing acceptor-based devices.

Abstract

Se-functionalized small molecule acceptors (SMAs) exhibit unique advantages in constructing materials with near-infrared absorption, but their photovoltaic performance lags behind that of S-containing analogs in organic solar cells (OSCs). Herein, two new Se-containing SMAs, namely Se-EH and Se-EHp, are designed and synthesized by regulating bifurcation site of outer alkyl chain, which enables Se-EH and Se-EHp to form different 3D crystal frameworks from CH1007. Se-EH displays tighter π–π stacking and denser packing framework with smaller-sized pore structure induced by larger steric hindrance effect of outer alkyl chain branched at 2-position, and a higher dielectric constant of PM6:Se-EH active layer can be obtained. OSCs based on PM6:Se-EH achieved very high PCEs of 18.58% in binary and 19.03% in ternary devices with a high FF approaching 80% for Se-containing SMAs. A more significant alkyl chain steric hindrance effect in Se-EH adjusts the molecular crystallization to form a favorable nanofiber interpenetrating network with an appropriate domain size to reduce rate of sub-ns recombination and promote balanced transport of carriers. This work provides references for further design and development of highly efficient Se-functionalized SMAs.

The PEDOT:PSS is deposited on the Me-4PACz to form a composite hole-transport interface layer. There is a built-in potential inside the composite interlayer due to the change in work function, which is beneficial for hole collection and results in low nonradiative recombination rate. As a result, the high power conversion efficiency of 18.70% is achieved for binary all-polymer solar cells.

Abstract

Trap states in organic solar cells (OSCs) can capture free charges, leading to a reduction in current density and significant energy loss. Since charge collection is primarily dependent on the interface layer, minimizing trap states at interfaces can effectively suppress energy losses, a topic that has been rarely explored. Herein, an interface strategy is proposed by combining Me-4PACz and PEDOT:PSS to mitigate the trap-assisted nonradiative recombination at the hole transport layer (HTL). OSCs based on the Me-4PACz/PEDOT:PSS exhibit reduced trap densities and low energy losses compared to devices fabricated with a single-layer HTL. This reduction can be attributed to a lower nonradiative recombination rate during hole transport at the interface. Changes in the work function of the two interlayers due to contact result in the existence of a built-in potential inside the composite interlayer, promoting charge collection and reducing energy loss from charge recombination. Furthermore, the composite HTL interface induces vertical phase separation of active layer, leading to significant improvements of the fill factor for OSCs. As a result, high power conversion efficiencies (PCEs) of 18.70% and 19.02% are achieved for binary all-polymer solar cells and polymer donor/small molecule acceptor solar cells, respectively.

This review systematically summarizes defect formation causes, discusses the defect regulation strategies for all–inorganic PSCs from interface, internal, and surface engineering in recent years, and overviews the development in terrestrial ecosystem, alongside conducting an in-depth analysis and summary of their potential developmental stage under extreme conditions such as those encountered in space and underwater environments.

Abstract

All–inorganic perovskite solar cells (PSCs), such as CsPbX₃, have garnered considerable attention recently, as they exhibit superior thermodynamic and optoelectronic stabilities compared to the organic–inorganic hybrid PSCs. However, the power conversion efficiency (PCE) of CsPbX₃ PSCs is generally lower than that of organic–inorganic hybrid PSCs, as they contain higher defect densities at the interface and within the perovskite light-absorbing layers, resulting in higher non-radiative recombination and voltage loss. Consequently, defect regulation has been adopted as an important strategy to improve device performance and stability. This review aims to comprehensively summarize recent progresses on the defect regulation in CsPbX₃ PSCs, as well as their cutting-edge applications in extreme scenarios. The underlying fundamental mechanisms leading to the defect formation in the crystal structure of CsPbX₃ PSCs are firstly discussed, and an overview of literature-adopted defect regulation strategies in the context of interface, internal, and surface engineering is provided. Cutting-edge applications of CsPbX₃ PSCs in extreme environments such as outer space and underwater situations are highlighted. Finally, a summary and outlook are presented on future directions for achieving higher efficiencies and superior stability in CsPbX₃ PSCs.

A cross-linkable fullerene (FTAI) is applied to regulate grain boundary conductivity and elasticity for the tin-based perovskite. The introduction of FTAI not only improves the perovskite quality, passivates the grain boundary defects, and facilitates charge transfer, but also effectively enhances the mechanical stability of perovskite film, achieving high-performance rigid and wearable tin-based perovskite solar cells.

Abstract

Tin-based perovskite solar cells (TPSCs) have received increasing attention due to their low toxicity, high theoretical efficiency, and potential applications as wearable devices. However, the inherent fast and uncontrollable crystallization process of tin-based perovskites results in high defect density in the film. Meanwhile, when fabricated into flexible devices, the prepared perovskite film exhibits inevitable brittleness and high Young's modulus, seriously weakening the mechanical stability. In this work, we design and synthesize a cross-linkable fullerene, thioctic acid functionalized C₆₀ fulleropyrrolidinium iodide (FTAI), which has multiple interactions with perovskite components and can finely regulate the crystallization quality of perovskite film. The obtained perovskite film shows an increased grain size and a more matched energy level with the electron transport material, effectively improving the carrier extraction efficiency. The FTAI-based rigid device achieves a champion efficiency of 14.91 % with enhanced stability. More importantly, the FTAI located at the perovskite grain boundaries could spontaneously cross-link during the perovskite annealing process, which effectively improves the conductivity and elasticity of grain boundaries, thereby giving the film excellent bending resistance. Finally, the FTAI-based wearable device yields a record efficiency of 12.35 % and displays robust bending durability, retaining about 90 % of the initial efficiency after 10,000 bending times.

Nature Communications, Published online: 09 March 2024; doi:10.1038/s41467-024-46493-4

Publication date: 15 May 2024

Source: Joule, Volume 8, Issue 5

Author(s): Chunyang Zhang, Yoosang Son, Hyungjun Kim, Sun-Ho Lee, Xin Liang, Guiming Fu, Sang-Uk Lee, Dong-Am Park, Qi Jiang, Kai Zhu, Nam-Gyu Park

A comprehensive and systematic 2D optimization engineering offers the new chance to understanding homogenous processing solvent processed LBL organic solar cells and solid additive's typical role in tuning donor & acceptor morphology. The efficiency enhancement in this work differing from others represents a new possibility to explore performance limit by synergistic morphology regulation.

Abstract

Herein, two emerging device optimization methods, solid additive and layer-by-layer (LBL) process, for organic solar cells (OSCs) are simultaneously studied. Through traditional blend cast and recently proposed identical solvent LBL cast, BDCB (2-monobromo-1,3-dichloro-bezene), a benzene derivative, is used to improve the device performance based on celebrity combination PM6:L8-BO. The results reveal that finely optimized BDCB concentration in PM6 solution can push the efficiency of LBL to 19.03% compared to blend cast with only 18.12% while the power conversion efficiency (PCE) changing trend is determined by BDCB's ratio in L8-BO's precursor. The morphology characterizations confirm there exists no significant stratification for LBL-processed devices, supported by a previously reported swelling-intercalation-phase separation (SIPS) model. Thereby, the solid additive's 2D optimization is considered a smart strategy for finely tuning the SIPS process, which results in various final morphology states. This work not only reports a cutting-edge efficiency for binary OSCs, but also new insight and deep understanding for LBL method-based morphology optimization strategy development.