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[Display omitted] • The mesoporous TiO 2 film was chlorinated by HCl solution and first applied in perovskite solar cells. • It is the first time that the properties of the interface layer between TiO 2 and perovskite are regulated by HCl solution. • The efficiency of C-PSCs based on HCl aqueous solution treated m-TiO 2 layer increased by 7.96 %. • The C-PSCs based on chlorinated TiO 2 have an excellent stability on a large square of 1 cm2. Printable HTM-free (HTM = hole-transporting material) mesoporous carbon-based perovskite solar cells (C-PSCs) are one of the most promising technologies. In this study, a high-quality chlorinated mesoscopic TiO 2 (m-TiO 2) film was obtained by hydrochloric acid (HCl) wet chemical process and applied in C-PSCs based on TiO 2 /ZrO 2 /(5-AVA) x (MA) 1-x PbI 3 /C structures. Experimental results show that the PCE of chlorinated m-TiO 2 C-PSCs greatly improved. Based on (5-AVA) x (MA) 1-x PbI 3 , C-PSCs with TiO 2 ETL treated with HCl aqueous solution achieved an average photovoltaic conversion efficiency of 9.36 %, which is an increase of 7.96 % in comparison with the efficiency of the device using unmodified TiO 2 ETL, while the V oc and the J sc were increased by 3.63 % and 2.63 %, respectively. In a 30-day aging test, C-PSCs based on (5-AVA) x (MA) 1-x PbI 3 and TiO 2 -HCl 1 exhibited excellent stability under ambient air conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bilateral passivation strategy by PEACl doping and NPB post-treatment is proposed. • Construction of GHJ provides a favorable transport pathway for hole migration. • Achieving a PCE of 21.88% for PEACl-SnO 2 -NPB based PSCs with negligible hysteresis. • Improved moisture and thermal stability of PSCs by using synchronous regulation. Defects and inferior charge transport dynamics within devices are key issues that inhibit the improvements of photovoltaic performance and stability. Developing facile and feasible strategies for synchronous passivation of defects regarding charge transport layers (CTLs), perovskite films and their interfaces, and precise tuning of energy level structure, is a definite way to solve above problems. Herein, we develop a synergistic passivation strategy for perovskite films and bilateral interfaces to improve device performance. Firstly, an appropriate amount of phenylethylammonium chloride is adopted to modify SnO 2 electron transport layer (ETL). The complexation reaction between N atoms in –NH 2 and Sn4+ improve the agglomeration of SnO 2 nanoparticles and film quality of SnO 2 ETL. The presence of Cl− ions not only effectively fill oxygen vacancies within SnO 2 ETL, but also participate in regulating crystal growth dynamics of perovskite films, thus improving electron transport properties at interface. Subsequently, p-type conducting material N,N'-Bis-(1-naphthalenyl)-N,N'-bis-phenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) is introduced into anti-solvent chlorobenzene during the preparation of perovskite films to further regulate the crystal quality and achieve full-range defect passivation. Particularly, the introduction of NPB helps to construct a gradient heterojunction between upper perovskite film and SpiroOMeTAD hole transport layer, thus reducing the accumulation of hole carriers near interface and further suppressing current–voltage hysteresis behavior of devices. Additionally, the hydrophobicity of NPB and full range of defect passivation greatly enhance the humidity and thermal stability of devices. Finally, a high power conversion efficiency of 21.88% is obtained with suppressed hysteresis and enhanced long-term stability. This work highlights the role of full-range defect passivation on CTLs, perovskite absorption layers and interfacial charge transport properties, which provide a novel concept for constructing high-performance and stable perovskite devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Iodine ligand-coupled PbS QDs film was firstly used to modify ZnO ETLs to boost photovoltaic performance of PSCs. • Introducing PbS-TBAI layer improves crystal quality of perovskite and forms cascade energy band structure. • A maximum PCE of 20.53 % has been achieved in the PSCs based on ZnO/PbS-TBAI-80 ETLs. Zinc oxide (ZnO) was traditional cathode material for solar cells due to excellent photoelectric properties. However, when ZnO is used as electron transport layers (ETLs) in perovskite solar cells (PSCs), the occurred deprotonation reactions can easily lead to the decomposition of perovskite layer. Herein, we reported a simple and controllable low-temperature strategy to overcome above problem for achieving high-efficient and stable ZnO based planar PSCs, i.e. the colloidal PbS QDs and tetrabutylammonium iodide (TBAI) was sequentially spin-coated on ZnO ETLs and then mild post-annealing process was carried out to obtaining ZnO/PbS-TBAI compact layer. Due to the iodine ligands from TBAI, the PbS-TBAI films act as both surface wetting control layer and electric dipole layer to adjust the crystal growth of perovskite films and charge behavior within devices. The better non-wetting surface of ZnO/PbS-TBAI ETLs improves the crystallization of the perovskite films by suppressing heterogeneous nucleation. And the unique energy level alignment of ZnO/PbS-TBAI induced by tunable surface dipole moment of TBAI boosted hetero-interface charge extraction of PSCs. Consequently, the optimized ZnO/PbS-TBAI based PSCs exhibits the power conversion efficiency (PCE) of 20.53 %, which is the champion PCE of ZnO PSCs with MAPbI 3 as the absorption layer. Stability tests also proved that the PCE of ZnO/PbS-TBAI based PSCs remains more than 86 % after exposure to 40 % humidity for 30 days, which is much more superior to that of control device. We firstly used iodination PbS QD films in this work to achieve higher photovoltaic performance in ZnO based PSCs, which prompts the further application of QDs materials within optoelectronic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Inorganic HAuCl 4 doping combined organic NPB post-treatment strategy was proposed. • High PCE of 19.20% for Au@PEDOT:PSS/NPB PSCs is achieved on rigid substrate. • Flexible Au@PEDOT:PSS/NPB PSCs achieve 14.04% PCE with strong wrinkle resistance. • Improved hysteresis and stability of PSCs are realized via synchronous regulation. The further improvements in optoelectronic properties, hydrophobicity of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layers, as well as regulation of defect states within devices are essential to promote the continued development of inverted p-i-n rigid and flexible planar perovskite solar cells (PSCs). However, the strong hygroscopicity, poor surface morphology, lower work function and coil configuration of pristine PEDOT:PSS films are detrimental to their own performance and growth dynamics process of perovskites, often resulting in sever energy losses and poor device performance. Herein, hydrogen tetrachloroaurate (III) hydrate (HAuCl 4 ·3H 2 O) additive is combined with a conductive N,N'-Bis-(1-naphthalenyl)-N,N'-bis-phenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) buffer layer to boost device performance by systematically modulating PEDOT:PSS and perovskite film. Wherein, the redox reaction between PEDOT:PSS and HAuCl 4 can cause phase segregation of PEDOT:PSS, improving the hydrophobicity, electrical conductivity, work function and surface morphology of the films. The reduced gold nanoparticles will produce localized surface plasmon resonance effects, thus enhancing the utilization of solar radiation by perovskite films. Furthermore, the suitable energy level alignment of NPB layer relative to perovskite and Au@PEDOT:PSS films will sufficiently exploit the dissociative excitons to facilitate effective hole transport, and the N atoms in NPB can also passivate defects at the interface by binding to uncoordinated Pb2+ ions, thereby reducing non-radiative open-circuit voltage loss and increasing short-circuit current density. A high power conversion efficiency (PCE) of 19.20% can be achieved for MA 0.85 FA 0.15 PbI 3 based p-i-n PSCs with negligible hysteresis and enhanced stability of devices. Similarly, the corresponding flexible device achieves a PCE of 14.04% with improved crumpling durability throughout low temperature preparation conditions below 140 °C. Our work presents a facile method to prepare high-efficient inverted PSCs while achieving improved long-term device stability. [ABSTRACT FROM AUTHOR]

Recently, organic solar cells (OSCs) have received rapid boosts in the power conversion efficiency (PCE), due to progresses in materials and device engineering. Several groups have reported champion PCEs over 19% in single‐junction, ternary, and tandem OSCs. In addition to the concentrated focus on the new design of OSC active materials, buffer layer materials, used for the interface layer providing the functionalities of interface charge transport and collection in OSCs, are of critical importance for the optimization of PCE. Compared with the electron transport layers (ETL), the hole transport layers (HTLs) have received less attention and are still dominated by the commercial material poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), which has limitations for the efficiency and OSC device stability enhancement. In this Review, the recent progress in HTL materials, including the modifications for PEDOT:PSS, alternative HTL materials based on polymers and inorganic oxide materials, etc, is summarized. This review also provides a summative prospect aiming to help scientists apprehend the current possibilities and challenges in this field. [ABSTRACT FROM AUTHOR]

Knowledge learned from nature demonstrates that system performance can be enhanced and optimized by hierarchical structural design which has dramatically expanded implications for synthetic materials, from design to implementation. In recent years, numerous bioinspired and biomimetic strategies are devoted to design energy storage and harvesting devices. For these devices, efficient and stable electrode/electrolyte interfaces, modified interactions, and new functions are desired, which remain a challenge to fully meet the requirement of the rapidly developed electronic industry. This review, taking lithium batteries, nanogenerators and solar cells as examples, provides a summary and discussion of how the bio‐inspired strategies can influence the electrode/device design and the corresponding interface interactions. By applying and learning from biological materials, natural hierarchical structure, surface topography, and biochemical process, enhanced performance and stability for energy devices can be achieved. Future research expectations in this field and energy management are also discussed. [ABSTRACT FROM AUTHOR]

• We developed a "hillocks"-like random-textured perovskite (HRT-perovskite) absorber. • Crystallization kinetics and formation mechanisms of CB-induced HRT-perovskite absorbers have been proposed. • Proper volume CB promoted the construction of porous MAI-PbI 2 -DMSO intermediate structure. • Efficient light trapping was achieved by employing CB-induced HRT-perovskite absorbers. Efficient planar heterojunction perovskite solar cells (PSCs) with high-quality absorbers are promising for flexible-, semitransparent-, and tandem- photovoltaic applications. However, compared to mesoporous PSCs, planar perovskite absorbers tend to suffer from additional optical losses due to insufficient light harvesting. Accordingly, the design and fabrication of high-quality textured perovskite absorbers are promising to improve device performance. We developed a "hillocks"-like random-textured perovskite (HRT-perovskite) absorber using a facile chlorobenzene (CB) anti-solvent assisted spin-coating approach. The crystallization kinetics and formation mechanisms of CB-induced HRT-perovskite absorbers have been systematically explored, allowing us to gain insights into the role of CB, i.e. an appropriate volume of CB promotes the formation of a porous MAI-PbI 2 -DMSO intermediate structure. We show that the porous nature of the intermediate film provides sufficient space for lattice reconstruction and structure expansion during crystal growth, thus effectively improving the film and surface/interface quality, and, ultimately, the optoelectronic properties of the perovskite absorber. Moreover, the HRT-perovskite absorber exhibits excellent light-trapping capability and carrier mobility, due to its optimized surface roughness and longitudinally ordered grain boundary distribution. As a result, we obtained efficiencies of up to 20.03% from planar heterojunction PSCs fabricated using ~400 nm thick HRT-perovskite absorbers. The process exhibits very high reproducibility with 20 individual devices fabricated in one batch, achieving an average power conversion efficiency (PCE) of 19.00%. Finally, the whole fabrication process was conducted below 150 ℃, which is appropriate for a wide range of applications, such as flexible- and tandem- photovoltaic devices. [ABSTRACT FROM AUTHOR]

Unlike Pb‐based perovskites, it is still a challenge for realizing the targets of high performance and stability in mixed Pb–Sn perovskite solar cells owing to grain boundary traps and chemical changes in the perovskites. In this work, proposed is the approach of in‐situ tin(II) inorganic complex antisolvent process for specifically tuning the perovskite nucleation and crystal growth process. Interestingly, uniquely formed is the quasi‐core–shell structure of Pb–Sn perovskite–tin(II) complex as well as heterojunction perovskite structure at the same time for achieving the targets. The core–shell structure of Pb–Sn perovskite crystals covered by a tin(II) complex at the grain boundaries effectively passivates the trap states and suppresses the nonradiative recombination, leading to longer carrier lifetime. Equally important, the perovskite heterostructure is intentionally formed at the perovskite top region for enhancing the carrier extraction. As a result, the mixed Pb–Sn low‐bandgap perovskite device achieves a high power conversion efficiency up to 19.03% with fill factor over 0.8, which is among the highest fill factor in high‐performance Pb–Sn perovskite solar cells. Remarkably, the device fail time under continuous light illumination is extended by over 18.5‐folds from 30 to 560 h, benefitting from the protection of the quasi‐core–shell structure. [ABSTRACT FROM AUTHOR]

Electron transport layer (ETL) is one of the key functional layers for extracting carriers in perovskite solar cells (PSCs). SnO 2 with high electron mobility and excellent energy level matching with adjacent perovskites has been considered an ideal electron transport material with great application prospects. However, surface defects always exist on the SnO 2 films prepared by solution method, which will inevitably lead to non-radiation recombination at the interface of SnO 2 ETL/perovskite. To further improve the performance of PSCs, the defects should be effectively suppressed. Herein, an interfacial engineering strategy is adopted to eliminate the surface defects and improve the interface performance by passivating the SnO 2 electron transport layer with sodium L -ascorbate (SLA). After the SLA treatment, the interfacial defects of SnO 2 /perovskite film were reduced significantly and the electron transport was effectively facilitated by the denser SnO 2 layer, finally improving the power conversion efficiency (PCE) of PSCs. Besides, SLA neutralized the alkalinity of SnO 2 film, simultaneously improving the efficiency and stability of the device. As a result, the PCE of FA 0.74 MA 0.19 Cs 0.07 PbI 2.81 Cl 0.19 PSCs with active area of 0.09 cm2 was increased from 20.32 % to 22.70 %, and the larger area PSCs with active area 1.00 cm2 obtained a high PCE of 19.83 %. This work presents a convenient and effective passivation strategy for improving the ETL to promote the development of perovskite photovoltaic devices. [Display omitted] • Sodium L -ascorbate is introduced into ETL/perovskite interface. • The efficiency of charge extraction and transfer from perovskite layer to ETL is enhanced. • SLA-modified PSCs achieve a champion PCE of 22.70 % in small size (0.09 cm2) and 19.83 % in large size (1.00 cm2). • The optimal PSCs showed excellent stability under illumination. [ABSTRACT FROM AUTHOR]

The fragile framework of the organic–inorganic metal halide perovskite has been strengthened for improving the stability of the PSCs by a multifunctional 2-amino-acetamidobenzotrifluoride (called BDP) with –NH 2 , C=O, and -CF 3 groups, simultaneously yielding a high efficiency of 21.62% for MAPbI 3 -based solar cells. [Display omitted] • A novel BDP-perovskite composite was developed for efficient and stable PSCs. • The BDP improved perovskite quality by retarding crystallization process. • The perovskite framework is reinforced by forming N-H...F bond with BDP. • The PCE of the BDP-treated device increased to 21.62% with a high V oc of 1.21 V. Perovskite solar cells (PSCs) are one of the most prospective photovoltaic devices because of their excellent photoelectric properties, yet their stability remains challenging. Apart from the reported passivation or encapsulation strategies, reinforcing the inherent framework of the perovskite is recognized as a substantial approach to stabilizing the PSCs. Herein, a multifunctional 2-amino-acetamidobenzotrifluoride (called BDP) with –NH 2 , C = O, and -CF 3 moieties is meticulously screened to strengthen the perovskite framework. The electron-donating groups of the BDP (–NH 2 and C = O) can simultaneously modify the crystallization process and achieve passivation, which devoted to reducing defect density; -CF 3 is used as a hydrophobic chemical stabilizer to form a moisture-resistant layer on the perovskite surface and suppress the MA+ ion migration by forming a hydrogen bond. Notably, the presence of the BDP also achieves a better energy level matching at the perovskite/hole transfer layer interface. Consequently, the power conversion efficiency (PCE) of MAPbI 3 solar cells is remarkably improved from 18.47% to 21.62%. Compared with the control devices, the PCE remains relatively stable under harsh external environmental conditions. Furthermore, the BDP also inhibits the lead leakage of PSCs, which is conducive to environmental applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel TiON ETL with nitrogen-Rich surface is developed for efficient and stable PSCs. • The Ti- N -Pb electron transfer channel boosts the charge transfer at heterointerface. • The TiON ETL improve the perovskite crystallization and suppress the interface recombination. • A stable PSCs with a V oc of 1.18 V and the PCE of 21.06 % was achieved. The electron transport layers (ETLs) play a pivotal role in perovskite solar cells (PSCs), which affect the extraction and transfer of the photo-generated-electrons. To explore a superior ETL material, which can not only improve electron transporting but also reduce interface defects, is extremely important for the development of the PSCs. Herein, a hybrid ETL with amorphous titanium nitride and titanium oxides (a-TiN x /TiO 2 , abbreviated as TiON) is developed to polish the microstructure of the ETL/perovskite interface. The TiON layer can adjust the bandgap alignment to produce favorable cascade energy levels with perovskite layer and facilitate the carrier transfer at ETL/perovskite interface. Meanwhile, the N atoms in TiON ETL surface can bifacially passivate the buried interface of the perovskite layer and the surface of the TiO 2 , decreasing uncoordinated Pb2+ and Ti4+ defects and reducing non-radiative recombination. Consequently, the TiON-based MAPbI 3 solar cells attain the PCE as high as 21.06 % with an open-circuit voltage of 1.18 V. This research demonstrates that TiON and relative metal nitrides can be promising electron transport materials, which provide a reference to develop more high quality ETLs for photovoltaic application. [ABSTRACT FROM AUTHOR]

A supramolecular bridging strategy with 2, 5-diaminobenzotrifluorid (DTF) molecular binder as the repeating unit was introduced to form a supramolecular-perovskite composite. The supramolecular binder plays a role of bridging the perovskite crystal grains, passivating the traps states of the perovskite films and producing excellent environmental stability. [Display omitted] • A supramolecular bridging strategy with DTF as repeat unit was proposed. • Bridging effect induced by the S-DTF for perovskite films was revealed. • Moisture-resistant MAPbI 3 solar cells with excellent performance was achieved. • Photovoltaic performance of MAPbI 3 solar cells have been effectively improved. The manipulation of grain boundaries in polycrystalline perovskites is an indispensable consideration for the photovoltaic performance and environmental stability of solar cells, because perovskite films obtained by solution process will inevitably introduce many defects in the grain boundaries. Although additives based on small molecules have proven to be effective defect passivators, their high volatility and diffusibility cannot satisfy the stability requirements of perovskite films. As an upgraded approach, herein, we introduced a supramolecular bridging strategy with 2,5-diaminobenzotrifluorid (DTF) molecular binder as the repeating unit to form a supramolecular-perovskite composite. The supramolecular binder plays a role of bridging the perovskite crystal grains, passivating the traps states of the perovskite films and producing excellent environmental stability, which is superior to the conventional additive engineering. As a result, the power conversion efficiency of the MAPbI 3 solar cell has been significantly increased from 18.8% to 21.0 %. The perovskite solar cells with S-DTF maintaining 93% of their original efficiency for over 30 days (∼70% humidity) in air ambient without encapsulation, exhibiting an excellent long-term stability. This will inspire a wider range of ideas beyond the regular additive engineering for improving the performance of polycrystalline perovskite-based photoelectronic devices. [ABSTRACT FROM AUTHOR]

Photoelectric imbalance problems of rear transparent conductive electrodes (TCEs) limit the photovoltaic (PV) performance of bifacial planar heterojunction perovskite solar cells (PH–PSCs). We exploit the superior electrical advantages of 0-dimensional (0D) carbon quantum dots (C QDs), 1-dimensional (1D) silver nanowires (Ag NWs), and 2-dimensional (2D) ultrathin Ag films to develop a novel rear TCE with ideal photoelectric balance, i.e., Ag NW + C QD/Ag NW/molybdenum oxide (MoOx)/ultrathin Ag (denoted as A + C/A/M/A) rear TCE with a 0D/1D/2D composite structure. We show that C QDs fully fill the voids within the Ag NW network, which effectively accelerates the charge transfer/collection, thereby enhancing the PV output of PH-PSCs. Moreover, the film quality and photoelectric properties of the rear TCEs are further improved by depositing the MoOx/ultrathin Ag films onto the A + C composite network, which significantly improves PV performance. More importantly, MoOx is key to realizing the photoelectric balance of rear TCEs because it not only has excellent antireflection effects, but also promotes the formation of high-quality ultrathin Ag film. As a result, the efficiencies of the A + C/A/M/A-based PH-PSC under front and rear illuminations are 16.09% and 12.59%, respectively, which are superior to that of most reported Ag NW-based PSCs. [Display omitted] • A novel 0D/1D/2D composite rear TCE was constructed. • Photoelectric balance of the rear TCE was achieved. • MoOx promoted the formation of high-quality 2D ultrathin Ag films. • The effects of the rear TCEs on the photovoltaic parameters were clarified. [ABSTRACT FROM AUTHOR]

So far, squaraine‐based polymer donors have been less explored for the bulk heterojunction (BHJ) polymer solar cells. In this work, two new p–π conjugated polysquaraines (PASQ‐BDT1 and PASQ‐BDT2) with different electron‐rich subunits on the squaraine skeleton are rationally developed as new polymer donors based on the 2D structure design concept. PASQ‐BDT2 with N,N‐diisobutylaniline subunits shows superior device performances in both fullerene and nonfullerene PSCs compared to PASQ‐BDT1 containing triphenylamine subunits, with power conversion efficiencies (PCEs) of 4.34% and 3.72%, respectively, owing to increased light‐harvesting ability and more favorable nanoscale morphology in the BHJ films. Moreover, its demonstrated that solvent effects can play an effective role in elevating the device performance. For the PASQ‐BDT2/PC71BM blend, the PCE is improved from 3.19% to 4.34% after solvent vapor annealing treatment, mainly attributed to the optimized film morphology and increased hole mobility. More interestingly, when the processing solvent for nonfullerene devices is changed from chlorobenzene to chloroform, a significant enhancement on PCE from 1.96% to 3.72% is yielded for the PASQ‐BDT2/ITIC blend, due to suppressed charge recombination and enhanced crystallinity in the chloroform‐processed BHJ films. [ABSTRACT FROM AUTHOR]

Hole transport layer plays a critical role in achieving high performance and stable inverted perovskite solar cells (PSCs). Doping has been proved to be an effective strategy to modify the electrical and optical properties of semiconductor oxides. Herein, rare earths (REs: Ce, Nd, Eu, Tb, and Yb) elements are systemically doped into the NiO x hole transport layer (HTL) via a simple solution-based method. The results demonstrate that the REs doping could considerably modify the compactness, conductivity, and band alignment of the NiO x HTL, leading to the highly improved permanence of the inverted PSCs. The PSCs using 3% Eu:NiO x HTL yielded the optimum power conversion efficiency of 15.06%, relatively improved 23.4% compared with the PSC using pristine NiO x HTL (12.20%). It also demonstrated much better long time stability. The improved photovoltaic properties of the device can be attributed to the more efficient charge extraction and suppressed interfacial recombination rate by the introduction of appropriate REs in the NiO x HTL. This work indicates that RE doping is a very effective and promising strategy to achieve adjustable hole extraction material for high and stable inverted PSCs. Image 1 • REs (Ce, Nd, Eu, Tb, Yb) ions were doped into NiO x HTLs via solution method. • PSC using 3% Eu:NiO x exhibited the best PCE of 15.6%, with 23.4% improvement. • The improvement was attributed to the improved conductivity and perovskite layer. [ABSTRACT FROM AUTHOR]