Chen Weijie

Highly stable inorganic perovskite CsPbBr₃ nanocrystals are adapted to modify bulk FAPbI₃ perovskite films. An ion reservoir is achieved to support a simultaneous two-way ion exchange at the interface, which can supply and store both cations and halides. Defects are therefore effectively passivated, leading to improved charge carrier dynamics and overall enhancement of efficiency and stability of the fabricated photovoltaics.

Abstract

Bulk lead halide perovskite films with unique optoelectronic properties and facile low-cost processing methods are promising for various optoelectronic applications including photovoltaics. Solution-processed colloidal inorganic perovskite nanocrystals with higher crystallinity hold good potential for devices with better stability and optoelectronic properties. To address phase stability and defect passivation issues in black phase FAPbI₃ perovskite, all-inorganic perovskite CsPbBr₃ nanocrystals (CPB NCs) are adapted as an effective modifier to form CPB NC-treated FAPbI₃ perovskite films (noted as CPB NC-FAPbI₃). It is identified in this study that, the incorporated CsPbBr₃ NCs not only act as surface additives for the bulk perovskite films, but can also serve as ion reservoirs to supply both cation and halide exchanges at the interface. This two-way ion exchange in CPB NC-FAPbI₃ samples leads to the formation of a compositional gradient as FA_{1− x} Cs _x PbI_{3− y} Br _y layers on the bulk perovskite film surface with vertically varied x and y values. Defects at interfaces and grain boundaries are therefore effectively passivated, leading to improved stability and charge carrier dynamics. As a result, the CPB NC-FAPbI₃ perovskite based solar cells exhibit overall enhancements in device efficiency and operational stability.

An ethyl alcohol cosolvent strategy is applied for room-temperature blade-coated perovskite solar cells and minimodules. This approach delicately manipulates the balance between nucleation and crystal growth rate to guarantee high-quality perovskite films, thus achieving remarkable device performance both in small-area cells and minimodules with excellent V _OC deficit and suppressed nonradiative recombination loss.

Abstract

Manipulating the perovskite solidification process, including nucleation and crystal growth, plays a critical role in controlling film morphology and thus affects the resultant device performance. In this work, a facile and effective ethyl alcohol (EtOH) cosolvent strategy is demonstrated with the incorporation of EtOH into perovskite ink for high-performance room-temperature blade-coated perovskite solar cells (PSCs) and modules. Systematic real-time perovskite crystallization studies uncover the delicate perovskite structural evolutions and phase-transition pathway. Time-resolved X-ray diffraction and density functional theory calculations both demonstrate that EtOH in the mixed-solvent system significantly promotes the formation of an FA-based precursor solvate (FA₂PbBr₄·DMSO) during the trace-solvent-assisted transition process, which finely regulates the balance between nucleation and crystal growth to guarantee high-quality perovskite films. This strategy efficiently suppresses nonradiative recombination and improves efficiencies in both 1.54 (23.19%) and 1.60 eV (22.51%) perovskite systems, which represents one of the highest records for blade-coated PSCs in both small-area devices and minimodules. An excellent V _OC deficit as low as 335 mV in the 1.54 eV perovskite system, coincident with the measured nonradiative recombination loss of only 77 mV, is achieved. More importantly, significantly enhanced device stability is another signature of this approach.

The work function of Nb₂CT _x MXene is reduced from 4.65 to 4.32 eV through hydrazine treatment. The perovskite solar cells using treated Nb₂CT _x MXene as the electron transport layer and perovskite additive achieve the highest power conversion efficiency of 21.79% and exhibit good stability.

Abstract

Perovskite solar cells have shown great potential in commercial applications due to their high performance and easy fabrication. However, the electron transport layer (ETL) materials with good optoelectrical properties and energy levels matching that of the perovskite layer still need to be explored to meet the need of commercialization. In this work, 2D Nb₂CT _x MXene nanosheets are prepared and their work function (WF) is reduced from 4.65 to 4.32 eV to match the conduction band minimum of perovskite layer by replacing the surface -F groups with NH₂ groups through hydrazine (N₂H₄) treatment. Besides, the N₂H₄ treated (T-Nb₂CT _x ) MXene nanosheets with abundant NH₂ groups are incorporated into the perovskite precursor to retard the crystallization rate by forming hydrogen bond with iodine ions, which promotes the formation of high-quality and oriented growth perovskite films. Consequently, the PVSCs with T-Nb₂CT _x MXene ETLs and T-Nb₂CT _x MXene nanosheets additive exhibit the highest power conversion efficiency (PCE) of 21.79% and the corresponding flexible and large-area devices achieve the highest PCE of 19.15% and 18.31%. Meanwhile, the unencapsulated devices maintain 93% of the original PCEs after 1500 h of storage. This work demonstrates the considerable application prospects of 2D Nb₂CT _x MXene in photoelectric devices.

A novel small molecular donor, CNS-6-8, is synthesized and incorporated into the state-of-the-art ternary system PM6:Y6:PC₇₁BM to tune the interaction of donors and acceptors. An optimized active layer morphology with appropriate domains and ordered packing is achieved in the PM6:CNS-6-8:Y6:PC₇₁BM blend, affording an excellent power conversion efficiency of 18.07% with synchronously improved V _oc, FF, and comparable J _sc.

Abstract

A wide bandgap oligomer-like donor CNS-6-8 is synthesized and incorporated into the host PM6:Y6:PC₇₁BM system to tune the morphology of the active layer for better device performance. Due to the good miscibility of CNS-6-8 with both host donor (PM6) and acceptors (Y6 and PC₇₁BM), an optimized morphology is achieved with the appropriate phase separation size and enhanced crystallinity, which ultimately leads to more efficient exciton dissociation, charge transport, and lower nonradiative energy loss. As a result, the quaternary device achieves an improved efficiency of 18.07%, with a simultaneously increased open circuit voltage of 0.868 V, fill factor of 78.8%, and the comparable short-circuit current density of 26.43 mA cm⁻². This work indicates that the favorable 3D interpenetrating network morphology of Y6 containing blend films can be optimized by introducing small amount of a specific molecule with high crystallinity, thus providing an effective strategy to achieve better photovoltaic performance for state-of-the-art Y6 analogs-based organic solar cells.

In the last few years, impressive efforts have been made on scalable printing techniques for the fabrication of highly efficient perovskite solar cells (PSCs) and their commercialization. This review highlights on the scalable growth of high-quality perovskite films, carrier transport layers, and electrodes using several printing techniques. Also, forthcoming challenges, and scopes of these printing techniques are offered.

Abstract

Just over a decade, perovskite solar cells (PSCs) have been emerged as a next-generation photovoltaic technology due to their skyrocketing power conversion efficiency (PCE), low cost, and easy manufacturing techniques compared to Si solar cells. Several methods and procedures have been developed to fabricate high-quality perovskite films to improve the scalability and commercialize PSCs. Recently, several printing technologies such as blade-coating, slot-die coating, spray coating, flexographic printing, gravure printing, screen printing, and inkjet printing have been found to be very effective in controlling film formation and improving the PCE of over 21%. This review summarizes the intensive research efforts given for these printing techniques to scale up the perovskite films as well as the hole transport layer (HTL), the electron transport layer (ETL), and electrodes for PSCs. In the end, this review presents a description of the future research scope to overcome the challenges being faced in the printing techniques for the commercialization of PSCs.

The increase in butylammonium iodide (BAI) steric hindrance weakens its diffusion to grain boundary, resulting in excessive BAI residue on the surface of perovskite films. Because diffusion to grain boundary affects the passivation of grain boundaries and excessive BAI on the surface blocks hole transport, the photovoltaic performance of the device decreases gradually with the increase in BAI steric hindrance.

The efficiency and stability of perovskite solar cells (PSCs) can be effectively improved by interfacial modification with butylammonium iodide (BAI). However, the steric hindrance of BAI is not explored. Herein, BAI with different steric hindrances, that is, n-BAI, iso-BAI (i-BAI), and tert-BAI (t-BAI), are systematically studied as interface modification materials between (FAPbI₃)_0.95(MAPbBr₃)_0.05 and spiro-OMeTAD in PSCs. It is found that the efficiency and humidity stability of devices gradually increase in the order of t-BAI-, i-BAI-, n-BAI-modified ones. This seems that the larger steric hindrance hinders BAI diffusion to the grain boundary, resulting in the reduction of grain boundary passivation and the residue of excessive BAI on the surface of perovskite films. Excessive BAI is equivalent to new defects and can block hole transport. As the steric hindrance increases from n-BAI to i-BAI, and further to t-BAI, the device with n-BAI modification shows the highest power conversion efficiency (PCE) of 20.67% with excellent stability in air with a humidity of 20–30%, keeping 80% of the original PCE after 60 days. It is believed that this study can guide the structural selection of modified materials at the interface between perovskite and hole transport layer with n–i–p structure.

Two polymer acceptors with non-fused conjugated backbones are reported for the first time for all-polymer solar cells (all-PSCs), which possess synthetic simplicity, narrow bandgap, high absorption coefficient, and high electron mobility. A promising efficiency of 10.14% is achieved, indicating that polymerizing non-fused acceptors is an effective strategy to develop high-performance, yet low-cost polymer acceptors for all-PSCs.

The development of polymer acceptors is critical to promote the power conversion efficiencies (PCEs) of all-polymer solar cells (all-PSCs). Herein, two novel polymer acceptors (PBTz–TT and PFBTz–TT) derived from non-fused small molecules, which possess synthetic simplicity, narrow optical bandgap, and high absorption coefficients, are reported for the first time. The all-PSCs are fabricated by a layer-by-layer deposition technique with PBDB-T as donor, and the device performance is improved by the synergistic effect of solvent additive and thermal annealing. As a result, the all-PSCs offer PCEs of 10.14% and 6.85% for PFBTz-TT and PBTz-TT, respectively. Further morphological and electrical characterizations unveil that the higher device performance of PFBTz-TT originates from more efficient exciton separation and charge transport as a result of more ordered polymer packing in solid state. Herein, it is demonstrated that polymerizing non-fused small molecular acceptors is an effective strategy to develop polymer acceptors for high-performance all-PSCs.

4-bromobenzenesulfonyl chloride is introduced to modify the perovskite film to improve crystal quality, reduce nonradiative recombination, and passivate surface defects. As a consequence, the optimized device achieves a champion power conversion efficiency of 21.84%, and the efficiency can retain almost 80% of the original value after 1200 h.

Perovskite photovoltaics have drawn tremendous attention due to their excellent photoelectric performance and possess promising potential in the field of renewable energy. Although the photoelectric conversion efficiency of perovskite solar cells has made a quantum leap, stability is still a limitation to its long-term development and has become the main issue that needs to be solved urgently. The defects in the perovskite films and at the grain boundaries are important factors affecting the stability of perovskite photovoltaics. It is reported that the surface defect of the perovskite film is two to four orders of magnitude higher than the bulk defect. Herein, 4-bromobenzenesulfonyl chloride to modify the surface defects of perovskite films is introduced. Through the interaction between S = O in 4-bromobenzenesulfonyl chloride and the bare Pb²⁺ in the perovskite film, the crystal quality of the perovskite film is significantly improved and the surface defects are effectively passivated. The optimized device achieves a champion power conversion efficiency of 21.84%, and the efficiency can retain 92% of the initial value after 1200 h. This finding provides a method to improve the device performance of perovskite solar cells.

A combined application of benzylammonium thiocyanate surface modification and methylammonium chloride additive engineering is applied to improve film quality of Cs–FA double-cation perovskite, helping to achieve enlarged and monolithic perovskite grains, better interfacial properties, and passivate the nonradiative recombination centers. As a result, a distinguished power conversion efficiency of 22.3% is realized for gas-quenched inverted p–i–n perovskite solar cells.

Inverted perovskite solar cells (PSCs) prepared by the antisolvent method have achieved power conversion efficiencies (PCEs) of over 23%, but they are not ideal for device upscaling. In contrast, gas-quenched PSCs offer great potential for upscaling, but their performance still lags behind. Herein, the gas-quenched films through both surface and bulk modifications are upgraded. First, a novel surface modifier, benzylammonium thiocyanate, is found to allow remarkably improved surface properties, but the PCE gain is limited by the existence of longitudinally multiple grains. Thus, methylammonium chloride additive as a second modifier to realize monolithic grains is further utilized. Such an integrated strategy enables the average open-circuit voltage of the gas-quenched PSCs to increase from 1.08 to 1.15 V, leading to a champion PCE of 22.3%. Moreover, the unencapsulated device shows negligible degradation after 150 h of maximum power point operation under simulated 1 sun illumination in N₂.

Adopted seed-assisted growth strategy to induce high crystalline, low-bandgap FAPbI₃-based perovskite below the thermodynamic phase-transition temperature (at 100 °C). The α-CsPbBr₃ seeds directly induce hexagonal α-FAPbI₃ crystals during the very initial crystallization period even at ambient temperature. Meanwhile, CsPbBr₃ seeds supplied an oriented template for the following perovskite grains bottom-up growth. The power conversion efficiency reached 22% in methylammonium-free inverted perovskite solar cells.

Abstract

The traditional way to stabilize α-phase formamidinium lead triiodide (FAPbI₃) perovskite often involves considerable additions of methylammonium (MA) and bromide into the perovskite lattice, leading to an enlarged bandgap and reduced thermal stability. This work shows a seed-assisted growth strategy to induce a bottom-up crystallization of MA-free perovskite, by introducing a small amount of α-CsPbBr₃/DMSO (5%) as seeds into the pristine FAPbI₃ system. During the initial crystalization period, the typical hexagonal α-FAPbI₃ crystals (containing α-CsPbBr₃ seeds) are directly formed even at ambient temperature, as observed by laser scanning confocal microscopy. It indicates that these seeds can promote the formation and stabilization of α-FAPbI₃ below the thermodynamic phase-transition temperature. After annealing not beyond 100 °C, CsPbBr₃ seeds homogeneously diffused into the entire perovskite layer via an ions exchange process. This work demonstrates an efficiency of 22% with hysteresis-free inverted perovskite solar cells (PSCs), one of the highest performances for MA-free inverted PSCs. Despite absented passivation processes, open-circuit voltage is improved by 100 millivolts compared to the control devices with the same stoichiometry, and long-term operational stability retained 92% under continuous full sun illumination. Going MA-free and low-temperature processes are a new insight for compatibility with tandems or flexible PSCs.

A vertical compositional gradient within the active layer with a donor-enriched active-anode interface and an acceptor-enriched active-cathode interface can be achieved by sequential solution deposition treatment in PM6/PY-IT:PDI-2T device. As a result, charge transfer properties and exciton diffusion length are promoted with suppressed non-geminate recombination to deliver an outstanding power conversion efficiency of 16% in the all-polymer solar cells, which are verified with transient absorption, time-resolved photoluminescence, and capacitance-voltage measurements.

Abstract

All-polymer solar cells (all-PSCs) have received attention in recent years for their desirable properties in power conversion efficiency and long-term operational stability. However, it is still a big challenge to acquire an “ideal” vertical-phase distribution of polymer/polymer blends due to the non-ideal molecular conformations and mixing behaviors. Herein, a ternary-assisted sequential solution deposition (SSD) strategy is adopted to regulate the vertical compositional profile of all-PSCs. A favorable acceptor(donor)-enriched phase near the cathode(anode) can be obtained by a ternary-assisted SSD strategy. With such a compositional profile, the exciton yield and carrier density can be enhanced by the vertical component gradient. Remarkably, the non-geminate recombination is suppressed with an improved exciton diffusion length (15.36 nm) that delivers an outstanding power conversion efficiency over 16% of the ternary PM6/PY-IT:PDI-2T SSD devices. This work demonstrates the success of ternary-assisted SSD strategy in reorganizing the vertical-phase distribution, which provides a feasible route for a potential ternary device construction toward efficient all-polymer photovoltaics.

P5TCN-2F, a new polythiophene featuring cyano-group substituent is developed for organic solar cells (OSCs). Over 16% efficiency is achieved due to the largely reduced energy loss and the formation of favorable active layer morphology. This polymer also offers superior cost-efficiency balance owing to its prominent device performance and low synthetic complexity, suggesting the renaissance of polythiophene-based OSCs.

Abstract

Polythiophenes (PTs) are promising electron donors in organic solar cells (OSCs) due to their simple structures and excellent synthetic scalability. However, the device performance of PT-based OSCs is rather poor due mainly to large photon energy losses and an unfavorable active layer morphology. Herein, the authors report a new PT, which is abbreviated as P5TCN-2F and features cyano-group substituents for high-efficiency OSCs. The cyano-group endows P5TCN-2F with a deep-lying highest occupied molecular orbital energy level, which thereby contributed to high open-circuit voltage in OSCs as a result of reduced non-radiative recombination energy loss. Moreover, the cyano-group leads to strong interchain interaction, improved polymer crystallinity, and appropriate miscibility with the prevailing non-fullerene acceptors. Consequently, P5TCN-2F offers over 15% power conversion efficiency when blended with various Y-series non-fullerene acceptors (Y6, Y6-BO, eC9, and L8-BO). Particularly, a champion efficiency of 16.1% is obtained by the P5TCN-2F:Y6 blend, which is largely higher than that of any previous PT-based OSCs. Moreover, the average figure of merit of the active layer based on P5TCN-2F is much superior to that of benzodithiophene-based polymers. These results suggest the renaissance of PT-based OSCs and have opened an avenue to access high-performance materials for the large-scale production of OSC modules.

The present work demonstrates an efficient strategy of synchronously passivating dual defects with low formation energies via terdentate anchoring by the multifunctional molecule of 1,10-phenanthrolin-5-amine, which could serve as an efficient interfacial mediator and consequently boost the power conversion efficiency up to 24.06%.

Abstract

The ionic nature endows halide perovskites with intrinsic interfacial defects in the formed polycrystalline films, thus imposing the challenge of synchronously passivating these defects with low formation energies that directly account for the unsatisfied performance of perovskite solar cells (PSCs). By virtue of the theoretically proven capability of a three to four times enhancement of the formation energy of each defect of Pb-I antisite (Pb_I) and iodine vacancy (V_I), a new passivation molecule of 1,10-phenanthrolin-5-amine (PAA) is intentionally explored to synchronously passivate the dual defects. The pronounced passivation effect is experimentally verified by the sharp enhancement of the open-circuit voltage in ternary PSCs from the original 1.118 up to 1.207 V, as well as the construction of PAA-modified formamidinium lead iodide PSCs with a champion efficiency up to 24.06%, thus providing a universal alternative of addressing interfacial charge carrier dynamics and operational stability of PSCs that are bothered by the multiple interfacial defects.

The energy band alignment at the perovskite–transport layer (TL) heterojunctions determines the interfacial recombination rates. Therefore, some device structures need better passivation to demonstrate high photovoltaic efficiency. Moreover, changes in work function at one TL can affect recombination at the other. Mobile ions can enhance device performance by moving minority carriers away from the interfaces and consequently reduce interface recombination.

A key limitation in perovskite solar cell (PSC) performance is suboptimal electronic properties at the perovskite–transport layer (TL) interfaces, which result in parasitic nonradiative recombination. Interface recombination depends on the concentration of recombination-active defects, but as a recombination event requires both an electron and a hole, the magnitude and sign of charge accumulation at the perovskite–TL heterojunctions are also critical. Here, we employ a well-established numerical ion-electron drift-diffusion model of PSCs to illustrate how the work function of the transport layer is an important factor in determining the total recombination activity at the perovskite interfaces. We show that the equilibrium electrostatics of the perovskite–TL heterojunctions, which are determined by the work function difference between the two materials, can result in increased recombination rates for any given concentration of interface defects. As a case study, we compare PSCs incorporating a NiO_X hole transport layer with those with a spiro-OMeTAD. We show that the work function of NiO_X can induce greater electron accumulation at the perovskite–NiO_X interface, which leads to increased interface recombination. Finally, a higher ion concentration is found to be beneficial to overall device performance by displacing accumulated electrons or holes at the TL interfaces and thus reducing recombination rates.

A perovskite homojunction is constructed and its stability is characterized. In the homojunction, doping defects tend to compensate each other through interdiffusion, resulting in the weakening of the built-in electric field. Herein, phenethylammonium iodide is used to inhibit the defects diffusion, improving the stability of the perovskite homojunction and related solar cells.

Perovskite homojunction can promote the separation and oriented transportation of the photocarriers through the built-in electric field, and weaken the dependence of solar cells on the charge transport layer. Although the perovskite homojunction shows great advantages in improving device efficiency, it retains the inherent poor stability of perovskite materials. Herein, it is found that donor defects (MA⁺ interstitial, I⁻ vacancy, etc.) in the n-type layer are prone to compensate the acceptor defects (MA⁺ vacancy, I⁻ interstitial, etc.) in the p-type layer. This compensation behavior results from the diffusion of doping defects driven by a concentration gradient, which leads to the weakening of the built-in electric field. Furthermore, phenethylammonium iodide is introduced into the perovskite homojunction to inhibit the defect diffusion, which enhances the stability of the homojunction and the corresponding solar cells. After modification, the efficiency of perovskite homojunction solar cells is improved from 8.60% to 9.60%, and retains 80% (standard ≈30%) of initial efficiency after 1000 h aging.

All-inorganic low-dimensional cesium copper halide nanocrystals (Cs₃Cu₂I₅ NCs) were introduced into perovskite solar cells. The champion device modified by Cs₃Cu₂I₅ NCs not only exhibits remarkable promotion of the power conversion efficiency (PCE) from 19.88% to 22.03% and fill factor from 74.09% to 82.21%, but also retains 91.6% of initial PCE after 504 h under high moisture conditions.

Ion defects at surface and grain boundaries (GBs) of perovskite films are paramount factors that influence the power conversion efficiency (PCE) of organic–inorganic hybrid perovskite solar cells (PSCs). Various methods have been proposed to solve the problems, but it still remains a great challenge because of the sophisticated and multiplicity of these defects. Herein, a modification method is developed that all-inorganic low-dimensional cesium copper halide nanocrystals (Cs₃Cu₂I₅ NCs) are introduced to reduce the ionic defects of perovskite films at the surface and GBs. The champion device modified by Cs₃Cu₂I₅ NCs exhibits remarkable promotion of PCE from 19.88% to 22.03% and fill factor from 74.09% to 82.21%. The results show that the solid-state interdiffusion process occurs between the perovskite films and Cs₃Cu₂I₅ NCs, which can improve the crystallinity, reduce interfacial recombination loss, and enhance the interfacial carrier transport in PSCs. Especially, the element distribution of Cs₃Cu₂I₅ NCs in perovskite films affects the effectiveness of ionic defects passivation in the perovskite lattice. The PSCs device retains 91.6% of its initial PCE after 504 h under high moisture conditions. This work demonstrates an interfacial engineering strategy using the characteristic perovskite NCs, which provides a passivation method to achieve the high-performance PSCs.

COTIC-4F: PC₆₁BM: PTB7-Th together with CsPbCl₃:Yb³⁺, Ce³⁺, Cr³⁺ nanophosphors are integrated into perovskite solar cells (PSCs). The near-infrared spectral response is extended to 1100 nm. The power conversion efficiency increases significantly from 20.52% to 23.40%. This work represents an effective and general strategy for obtaining efficient and stable PSC devices with extremely broad spectral responses.

Abstract

Extending near-infrared (NIR) spectral response and increasing ultraviolet utilization is still a challenge in the context of improving power conversion efficiency (PCE) for perovskite solar cells (PSCs). In this work, to extend NIR light-harvesting of PSCs, a novel COTIC-4F: PC₆₁BM: PTB7-Th ternary organic bulk-heterojunction together with Au nanotriangles is integrated on the PSCs. The NIR spectral response is thus extended to 1100 nm. In fact, the COTIC-4F: PC₆₁BM: PTB7-Th layer enables multi-functional effects, which can serve as electron transport, trap passivation, and moisture barrier layer in addition to NIR light harvesting. For increasing UV utilization, CsPbCl₃:Yb³⁺, Ce³⁺, Cr³⁺ nanophosphors with photoluminescent quantum yield close to 200% are fabricated, which demonstrate excellent down-conversion ability. Then, CsPbCl₃: Yb³⁺, Ce³⁺, Cr³⁺/polymethylmethacrylate composite films are self-assembled on a hybrid device, resulting in a 6.2% relative enhancement of short circuit current density. After simultaneously improving the NIR and UV spectral response of device, the PCE is increased significantly from 20.52% to 23.40% and the Jsc is increased from 21.79 to 25.96 mA cm⁻², representing one of the highest PCE and maximum Jsc enhancements in the reported inverted hybrid organic/PSCs. This work represents an effective and general strategy for obtaining efficient and stable PSC devices with extremely broad spectral responses.

A new concept of oligomer-assisted high-performance organic solar cells (OSCs) was proposed. Developing the oligomer-assisted OSCs is a facile and general strategy with the combination of the advantages of both binary and ternary devices, which enables >18 % device efficiency together with improved stability.

Abstract

Although ternary organic solar cells (OSCs) have unique advantages in improving device performance, the morphology assembly in the ternary-phase would be more uncertain or complex than that in the binary-phase. Here, we propose a new concept of oligomer-assisted photoactive layers for high-performance OSCs. The formed alloy-like phase of the oligomer : host polymer blend enabled the oligomer-assisted OSCs to fuse the advantages of both binary and ternary devices, exhibiting substantially enhanced performance and stability compared to the control devices. With the addition of oligomers, outstanding efficiencies of 17.33 % for a PM6 : Y6 device, 18.32 % for a PM6 : BTP-eC9 device, and 17.13 % for a PM6/Y6 pseudo-bilayer device were achieved, all of which are one of the highest values in their corresponding fields. The improved performance originated from the downshift energy levels, enhanced light absorption, optimized blend morphology, favorable charge dynamics, and reduced non-radiative energy loss.

Publication date: 1 May 2022

Source: Electrochimica Acta, Volume 413

Author(s): Lusheng Liang, Qiu Xiong, Zilong Zhang, Yaming Yu, Peng Gao

In this review, the progress of wide-bandgap organic–inorganic hybrid perovskite solar cells (PSCs) are initially summarized and the issues of phase segregation and voltage loss are assessed. Then, the diverse applications of wide-bandgap PSCs in semitransparent devices, indoor photovoltaics, and tandem devices are discussed and their challenges and perspectives are evaluated.

Abstract

Under the groundswell of calls for the industrialization of perovskite solar cells (PSCs), wide-bandgap (>1.7 eV) mixed halide perovskites are equally or more appealing in comparison with typical bandgap perovskites when the former's various potential applications are taken into account. In this review, the progress of wide-bandgap organic–inorganic hybrid PSCs—concentrating on the compositional space, optimization strategies, and device performance—are summarized and the issues of phase segregation and voltage loss are assessed. Then, the diverse applications of wide-bandgap PSCs in semitransparent devices, indoor photovoltaics, and various multijunction tandem devices are discussed and their challenges and perspectives are evaluated. Finally, the authors conclude with an outlook for the future development of wide-bandgap PSCs.

This review summarizes the recent advances of SnO₂-based perovskite solar cells (PSCs) and the related interface optimization strategies and applications. The fundamental properties of SnO₂ are discussed, with a focus on the defect chemistry, and various preparation methods for improving SnO₂ and SnO₂/perovskite interface. Finally, the challenges and opportunities for further development of SnO₂-based PSCs are provided.

Abstract

Perovskite solar cells (PSCs) based on the regular n–i–p device architecture have reached above 25% certified efficiency with continuously reported improvements in recent years. A key common factor for these recent breakthroughs is the development of SnO₂ as an effective electron transport layer in these devices. In this article, the key advances in SnO₂ development are reviewed, including various deposition approaches and surface treatment strategies, to enhance the bulk and interface properties of SnO₂ for highly efficient and stable n–i–p PSCs. In addition, the general materials chemistry associated with SnO₂ along with the corresponding materials challenges and improvement strategies are discussed, focusing on defects, intrinsic properties, and impact on device characteristics. Finally, some SnO₂ implementations related to scalable processes and flexible devices are highlighted, and perspectives on the future development of efficient and stable large-scale perovskite solar modules are also provided.