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The hole‐transporting material (HTM), poly (3,4‐ethylene dioxythiophene) poly(styrene sulfonate) (PEDOT : PSS), is the most widely used material in the realization of high‐efficiency organic solar cells (OSCs). However, the stability of PEDOT : PSS‐based OSCs is quite poor, arising from its strong acidity and hygroscopicity. In addition, PEDOT : PSS has an absorption in the infrared region and high highest occupied molecular orbital (HOMO) energy level, thus limiting the enhancement of short‐circuit current density (Jsc) and open‐circuit voltage (Voc), respectively. Herein, two asymmetric self‐assembled molecules (SAMs), namely BrCz and BrBACz, were designed and synthesized as HTM in binary OSCs based on the well‐known system of PM6 : Y6, PM6 : eC9, PM6 : L8‐BO, and D18 : eC9. Compared with BrCz, BrBACz shows larger dipole moment, deeper work function and lower surface energy. Moreover, BrBACz not only enhances photon harvesting in the active layer, but also minimizes voltage losses as well as improves interface charge extraction/ transport. Consequently, the PM6 : eC9‐based binary OSC using BrBACz as HTM exhibits a champion efficiency of 19.70 % with a remarkable Jsc of 29.20 mA cm−2 and a Voc of 0.856 V, which is a record efficiency for binary OSCs so far. In addition, the unencapsulated device maintains 95.0 % of its original efficiency after 1,000 hours of storage at air ambient, indicating excellent long‐term stability. [ABSTRACT FROM AUTHOR]

The main obstacles to promoting the commercialization of perovskite solar cells (PSCs) include their record power conversion efficiency (PCE), which still remains below the Shockley–Queisser limit, and poor long‐term stability, attributable to crystallographic defects in perovskite films and open‐circuit voltage (Voc) loss in devices. In this study, potassium (4‐tert‐butoxycarbonylpiperazin‐1‐yl) methyl trifluoroborate (PTFBK) was employed as a multifunctional additive to target and modulate bulk perovskite defects and carrier dynamics of PSCs. Apart from simultaneously passivating anionic and cationic defects, PTFBK could also optimize the energy‐level alignment of devices and weaken the interaction between carriers and longitudinal optical phonons, resulting in a carrier lifetime of greater than 3 μs. Furthermore, it inhibited non‐radiative recombination and improved the crystallization capacity in the target perovskite film. Hence, the target rigid and flexible p‐i‐n PSCs yielded champion PCEs of 24.99 % and 23.48 %, respectively. More importantly, due to hydrogen bonding between formamidinium and fluorine, the target devices exhibited remarkable thermal, humidity, and operational tracking at maximum power point stabilities. The reduced Young's modulus and residual stress in the perovskite layer also provided excellent bending stability for flexible target devices. [ABSTRACT FROM AUTHOR]

Molecular stacking and orientation are of great importance in regulating optoelectronic properties. Typically, the face‐on orientation of hole transporting materials (HTMs) is considered to be a prerequisite for the realization of high efficiency perovskite solar cells (PSCs). Herein, a small molecule HTM, BDT‐p‐IDN, is developed with edge‐on orientation by replacing the terminal group from diphenylamine to indoline unit. Remarkably, the PSCs device based on dopant‐free BDT‐p‐IDN exhibits an efficiency of 23.28%, which is comparable to that of its face‐on control BDT‐DPA‐F. Compared to BDT‐DPA‐F, BDT‐p‐IDN has stronger interaction with the perovskite (PVK) film and therefore stronger hole extraction and defect passivation capabilities, resulting in an increased short circuit current density and improved efficiency. The results indicate that edge‐on orientation could be a powerful way for HTMs to realize efficient PSCs. [ABSTRACT FROM AUTHOR]

Organic solar cells (OSCs) have attracted a great deal of attention in the field of clean solar energy due to their advantages of transparency, flexibility, low cost and light weight. Introducing them to the market enables seamless integration into buildings and windows, while also supporting wearable, portable electronics and internet-of-things (IoT) devices. With the development of photovoltaic materials and the optimization of fabrication technology, the power conversion efficiencies (PCEs) of OSCs have rapidly improved and now exceed 20%. However, there is a significant lack of focus on material stability and device lifetime, causing a severe hindrance to commercial applications. In this review, we carefully review important strategies employed to improve the stability of OSCs over the past three years from the perspectives of material design and device engineering. Furthermore, we analyze and discuss the current important progress in terms of air, light, thermal and mechanical stability. Finally, we propose the future research directions to overcome the challenges in achieving highly stable OSCs. We expect that this review will contribute to solving the stability problem of OSCs, eventually paving the way for commercial applications in the near future. [ABSTRACT FROM AUTHOR]

In recent years, the surface modification of perovskite by wide band‐gap insulating materials has been one of the main strategies to achieve efficient and stable perovskite solar cells (PSCs). Unfortunately, a significant hurdle in this approach is the dilemma surrounding the quality of passivation and the transport of charges. Here, this trade‐off is overcome by introducing self‐assembled diphenylphosphinic acid (DPPA) porous layer. Applying highly concentrated DPPA solution on the perovskite surface not only provides excellent passivation of entire surface, but also the excess DPPA will form a self‐assembled porous insulating layer (PIL), which forms random submicron‐sized openings at the interface of the insulating layer for accelerated charge transport. In addition, the energy level of the perovskite surface can be modulated by this insulating material to facilitate carrier transport. As a result, an impressive power conversion efficiency (PCE) over 24% has been achieved in methylammonium‐free p‐i‐n devices with an ultrahigh fill factor (FF) of 84.7%. The unencapsulated devices exhibit excellent thermal and operational stability. This work paves a way for establishment of an effective passivation and facilitated transport simultaneously. [ABSTRACT FROM AUTHOR]

The wearable application of flexible organic solar cells (f‐OSCs) necessitates high power conversion efficiency (PCE) and mechanical robustness. However, photoactive films based on efficient non‐fullerene small molecule acceptors (NF‐SMAs) are typically brittle, leading to poor mechanical stability in devices. In this study, we achieved a remarkable PCE of 18.06 % in f‐OSCs while maintaining ultrahigh mechanical robustness (with a crack‐onset strain (COS) of higher than 11 %) by incorporating a linker dimerized acceptor (DOY‐TVT). Compared to binary blends, ternary systems exhibit reduced non‐radiative recombination, suppressed crystallization and diffusion of NF‐SMAs, and improved load distribution across the chain networks, enabling the dissipation of the load energy. Thus, the ternary f‐OSCs developed in this study achieved, high PCE and stability, surpassing binary OSCs. Moreover, the developed f‐OSCs retained 97 % of the initial PCE even after 3000 bending cycles, indicating excellent mechanical stability (9.1 % higher than binary systems). Furthermore, the rigid device with inverted structure based on the optimal active layer exhibited a substantial increase in efficiency retention, with 89.6 % after 865 h at 85 °C and 93 % after more than 1300 h of shelf storage at 25 °C. These findings highlight the potential of the linker oligomer acceptor for realizing high‐performing f‐OSCs with ultrahigh mechanical robustness. [ABSTRACT FROM AUTHOR]

Substantial efforts of A–DA′D–A type non‐fullerene acceptors (NFAs) molecular design have impelled power conversion efficiency (PCE) of single junction organic solar cells (OSCs) to exceed 19%. Asymmetric geometry strategy, selenium‐substitution, and end‐group engineering are proven to be effective modification methods. Here, two novel selenium substitution asymmetric NFAs, AsymSSe‐2F, and AsymSSe‐2Cl, are synthesized to investigate the synergistic modification effects on device performance compared with symmetric Y6. When blending AsymSSe‐2F with the wide‐bandgap and high crystallinity polymer D18, a remarkable PCE of 18.31% is yielded, and an excellent fill factor of 79.46% is achieved, which is attributed to the broadened absorption, enhanced π–π stacking, balanced carrier mobilities, and fine phase‐separation morphology. Notably, among the reported selenium‐substituted asymmetric NFAs based OSCs, especially combined with the seldom‐reported D18, this PCE is top‐ranked in binary bulk heterojunction organic solar cells. This work indicates that the combined modification of asymmetric geometry and selenium substitution in NFAs is a promising strategy for fabricating high performance OSCs. [ABSTRACT FROM AUTHOR]

Despite the great progress of flexible perovskite solar cells (f‐PSCs), it still faces several challenges during the homogeneous fabrication of high‐quality perovskite thin films, and overcoming the insufficient exciton dissociation. To the ends, we rationally design the ferroelectric two‐dimensional (2D) perovskite based on pyridine heterocyclic ring as the organic interlayer. We uncover that incorporation of the ferroelectric 2D material into 3D perovskite induces an increased built‐in electric field (BEF), which enhances the exciton dissociation efficiency in the device. Moreover, the 2D seeds could assist the 3D crystallization by forming more homogeneous and highly‐oriented perovskite crystals. As a result, an impressive power conversion efficiency (PCE) over 23 % has been achieved by the f‐PSCs with outstanding ambient stability. Moreover, the piezo/ferroelectric 2D perovskite intrigues a decreased hole transport barriers at the ITO/perovskite interface under tensile stress, which opens new possibilities for developing highly‐efficient f‐PSCs. [ABSTRACT FROM AUTHOR]

As a multigroup cross‐linking agent, amino acid derivatives contain different kinds of characteristic functional groups with different characteristics. Aiming at one of the most difficult problems, ionic defects, amino acid derivatives can passivate these defects through their multifunctional groups. Ionic defects (such as organic cations and halogen anions) mostly exist on surface and/or grain boundaries of perovskite films, and amino acid derivatives promote the formation of high‐quality perovskite films by coordinating well with these defects. Herein, the effects of two kinds of amino acids (l‐arginine and l‐glutamic acid) with contrastive isoelectric points (pIs) on perovskite film formation, defect passivation mechanism, device efficiency, flexible substrate, and thermal/moisture stability are studied. Efficiency of inverted perovskite solar cells is improved from ≈20% to nearly 23% with additives on rigid substrates. High pI l‐arginine improves the open‐circuit voltage significantly, while low pI l‐glutamic acid excels in fill factor and short‐circuit current. More importantly, low pI l‐glutamic acid shows superior thermal and moisture stability, indicating inherent stronger bonding between l‐glutamic acid and perovskite. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Inverted (p‐i‐n) perovskite solar cells (PSCs) are favored by researchers owing to their superior compatibility with flexible substrates and tandem device fabrication. Additionally, the hole transport layer (HTL) serves as a template for perovskite growth, which is critical for enhancing the device performance. However, the current research on how the HTL promotes perovskite crystallization is insufficient. Here, 4PADCB, a self‐assembled monolayer (SAM) hole transport material, was optimized as a superior template for perovskite growth through comparative analysis; accordingly, compact perovskite film with vertical growth was prepared. The better matched energy level alignment between 4PADCB and perovskite suppressed nonradiative recombination at the interface and enabled rapid hole extraction. Moreover, high‐quality perovskite film growth on 4PADCB exhibited lower Young's modulus and less residual stress. By integrating 4PADCB into p‐i‐n PSCs, the optimal device achieved a power conversion efficiency of 24.80%, with an open‐circuit voltage of 1.156 V, thus achieving the best rank among devices without perovskite post‐treatment, additives, dopants, or intermediate layers. Furthermore, the unencapsulated device demonstrated exceptional thermostability and photostability under maximum power point tracking. Thus, this work provides a new understanding for the development of novel SAMs and perovskite growth, and it is expected to further improve device performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two non-fullerene donors with A-π-A'-π-A type structures designed and synthesised. • The structures contain 3-hexylrhodanine and 2-butyl cyanoacetate end groups. • The introduction of DB-1/2 achieved dual FRET in PM6:Y6 system for the first time. • The excessive self-aggregation of Y6 was broken in ternary solar cells. • The ternary organic solar cells achieve high J SC of 28.0 mA cm−2. Organic solar cells (OSCs) have aroused widespread concerns in green energy and wearable electronics. One of the most powerful way to achieve high efficient OSCs is maximizing fill factor (FF) and short-circuit current density (J SC). Herein, two A-π-A'-π-A type conjugated molecules bearing different electron-deficient end groups, DB-1 and DB-2, were designed and synthesized as donor-typed third components in the well-known PM6:Y6 host system. The photoluminescence and ultrafast transient absorption spectra clearly demonstrated that dual Förster resonance energy transfer (FRET) effects were well established for the first time in the PM6:Y6-based ternary OSCs. Furthermore, the introduction of DB-1 and DB-2 could effectively prevent the excessive self-aggregation of Y6, resulting in the optimal phase separations in the ternary films. Thus, the ternary OSCs based on PM6:DB-1:Y6 and PM6:DB-2:Y6 both achieved excellent J SC of ∼28.0 mA cm−2 and high FF ∼0.780, which are significantly higher than those of the binary devices. Consequently, rational molecular design and dual FRET effects provide a new and effective method to simultaneously improve the J SC and FF of OSCs. [ABSTRACT FROM AUTHOR]