Graded bulk-heterojunction (G-BHJ) with well-defined vertical phase separation has potential to surpass classical BHJ in organic solar cells (OSCs). In this work, an effective G-BHJ strategy via ...nonhalogenated solvent sequential deposition is demonstrated using nonfullerene acceptor (NFA) OSCs. Spin-coated G-BHJ OSCs deliver an outstanding 17.48% power conversion efficiency (PCE). Depth-profiling X-ray photoelectron spectroscopy (DP-XPS) and angle-dependent grazing incidence X-ray diffraction (GI-XRD) techniques enable the visualization of polymer/NFA composition and crystallinity gradient distributions, which benefit charge transport, and enable outstanding thick OSC PCEs (16.25% for 300 nm, 14.37% for 500 nm), which are among the highest reported. Moreover, the nonhalogenated solvent enabled G-BHJ OSC via open-air blade coating and achieved a record 16.77% PCE. The blade-coated G-BHJ has drastically different D-A crystallization kinetics, which suppresses the excessive aggregation induced unfavorable phase separation in BHJ. All these make G-BHJ a feasible and promising strategy towards highly efficient, eco- and manufacture friendly OSCs.
For organic solar cells to be competitive, the light-absorbing molecules should simultaneously satisfy multiple key requirements, including weak-absorption charge transfer state, high dielectric ...constant, suitable surface energy, proper crystallinity, etc. However, the systematic design rule in molecules to achieve the abovementioned goals is rarely studied. In this work, guided by theoretical calculation, we present a rational design of non-fullerene acceptor o-BTP-eC9, with distinct photoelectric properties compared to benchmark BTP-eC9. o-BTP-eC9 based device has uplifted charge transfer state, therefore significantly reducing the energy loss by 41 meV and showing excellent power conversion efficiency of 18.7%. Moreover, the new guest acceptor o-BTP-eC9 has excellent miscibility, crystallinity, and energy level compatibility with BTP-eC9, which enables an efficiency of 19.9% (19.5% certified) in PM6:BTP-C9:o-BTP-eC9 based ternary system with enhanced operational stability.
Perovskite solar cells (PSCs) are ideally fabricated entirely via a scalable solution process at low temperatures to realize the promise of simple manufacturing, low‐cost processing, compatibility ...with flexible substrates, and perovskite‐based tandem solar cells. However, high‐quality photoactive perovskite thin films under those processing conditions is a challenge. Here, a laminar air‐knife‐assisted room‐temperature meniscus coating approach that enables one to control the drying kinetics during the solidification process and achieve high‐quality perovskite films and solar cells is devised. Moreover, this approach offers a solid model platform for in situ UV–vis and microscopic investigation of the perovskite film drying kinetics, which provide rich insights correlating the degree of supersaturation, the nucleation, and growth rate during the kinetic drying process, and ultimately, the film morphology and performance of the solar cell devices. Manufacturing friendly, antisolvent‐free room‐temperature coating of hysteresis‐free PSCs with a power conversion efficiency of 20.26% for 0.06 cm2 and 18.76% for 1 cm2 devices is demonstrated.
Through a laminar air‐knife‐assisted room‐temperature meniscus coating, assisted by in situ UV–vis and microscopes, fundamental mechanisms of perovskite nucleation and crystal growth are investigated. Upon in‐depth film formation understanding, hysteresis‐free perovskite solar cell with a power conversion efficiency of 20.26% for 0.06 cm2 and 18.76% for 1 cm2 devices are successfully demonstrated by manufacturing a friendly room‐temperature meniscus coating process.
Epitaxial growth gives the highest‐quality crystalline semiconductor thin films for optoelectronic devices. Here, a universal solution‐processed bottom‐up quasi‐epitaxial growth of highly oriented ...α‐formamidinium lead triiodide (α‐FAPbI3) perovskite film via a two‐step method is reported, in which the crystal orientation of α‐FAPbI3 film is precisely controlled through the synergetic effect of methylammonium chloride and the large‐organic cation butylammonium bromide. In situ GIWAXS visualizes the BA‐related intermediate phase formation at the bottom of film, which serves as a guiding template for the bottom‐up quasi‐epitaxial growth in the subsequent annealing process. The template‐guided epitaxially grown BAFAMA perovskite film exhibits increased crystallinity, preferred crystallographic orientation, and reduced defects. Moreover, the BAFAMA perovskite solar cells demonstrate decent stability, maintaining 95% of their initial power conversion efficiency after 2600 h ambient storage, and 4‐time operation condition lifetime enhancement.
A universal solution‐processed bottom‐up quasi‐epitaxial growth of highly oriented α‐FAPbI3 perovskite film is achieved through the synergetic effect of methylammonium chloride and a large‐organic cation. In situ GIWAXS visualizes the BA‐related intermediate phase formation at the bottom, which serves as a guiding template for the bottom‐up quasi‐epitaxial growth in the subsequent annealing process.
Two regioisomeric wide-bandgap (WBG) polymers, PDBT(E)BTz-
p
and PDBT(E)BTz-
d
, with different nitrogen topologies along the conjugated backbone were developed and applied in non-fullerene polymer ...solar cells. Both polymers exhibit deeper ionization potential (IP) enabled by the synergistic electron-withdrawing effect of chlorine atoms and ester substituents. The effects of different nitrogen topologies on polymeric backbone linearity and optoelectronic and photovoltaic properties are systematically investigated. When blended with the electron acceptor IT-4F, the PDBT(E)BTz-
p
-based device delivers a PCE of 6.96% with a high
V
OC
of 0.98 V and a low energy loss of 0.55 eV, while the PDBT(E)BTz-
d
-based device exhibits a higher PCE of 7.81% with an improved FF. Furthermore, PDBT(E)BTz-
d
is found to be effective as the third component in a binary PBDB-T-SF:IT-4F system to enhance device efficiencies from 12.1% for the binary device to 13.4% for the ternary device with 5 wt% PDBT(E)BTz-
d
relative to PBDB-T-SF. It is observed that an internal Förster resonance energy transfer (FRET) between PDBT(E)BTz-
d
and PBDB-T-SF gives rise to the improvement of external quantum efficiency and
J
SC
. These results demonstrate that the WBG polymer featuring deeper IP can not only enhance the
V
OC
but can also act as a sensitizer to transfer energy through the FRET mechanism toward highly efficient ternary PSCs. In addition, this contribution provides a new idea for the design and synthesis of conjugated polymers for organic electronics.
Two regioisomeric wide-bandgap polymers with different nitrogen topologies along the conjugated backbone were developed and applied in non-fullerene polymer solar cells.
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 VOC 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.
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 VOC deficit and suppressed nonradiative recombination loss.
Although massive progress in power conversion efficiencies (PCEs) has been made on organic solar cells (OSCs), the challenge remains to scale up high-performance OSCs that are compatible with ...industrial production conditions, such as post-treatment-insensitive, non-halogenated solvent, large-area printing, processing under atmospheric environment. In this study, two A-D-A-D-A type oligomers, named
5BDDBDT-F
and
5BDDBDT-Cl
, were designed and synthesized to be incorporated into binary OSCs.
Ex situ
and
in situ
characterizations were performed to reveal the underlying working mechanisms. The two-phase transitions: liquid-to-liquid and liquid-to-solid can be synergistically tailored to promote the molecular arrangement of the binary blend. Benefiting from the enhanced crystallinity, the oligomer can act as a bridging linker to rehabilitate the interfacial defects to reduce the trap-assisted recombination losses and thus the non-radiative recombination losses. As a result, using non-halogenated solvent (
o
-xylene), the best-performing OSCs with PCEs of 18.32% with a
V
OC
of 0.850 V, an FF of 79.15% were achieved based on the
PM6
:
5BDDBDT-F
:
BTP-eC9
ternary OSCs, and 18.43% with a
V
OC
of 0.854 V, an FF of 79.29% were obtained based on
PM6
:
5BDDBDT-Cl
:
BTP-eC9
ternary OSCs without any post-processing. More importantly, it is noteworthy that the large-area (1 cm
2
) blade coated devices based on
PM6
:
5BDDBDT-F
:
BTP-eC9
and
PM6
:
5BDDBDT-Cl
:
BTP-eC9
, processed using non-halogenated solvent in an open-air environment without thermal-annealing treatment, obtained high PCE values of 17.11% and 17.06%, respectively, which are among the highest PCE values of blade-coated OSCs in open air. This study demonstrated an efficient strategy of controlling crystallization kinetics to improve the material crystallinity, as an effective guideline for achieving high photovoltaic performance in printing ternary OSCs, pushing the OSCs towards future manufacturing.
Two novel oligomers boost the 1 cm
2
device to achieve a remarkable PCE exceeding 17% using a green solvent in open-air without post-treatment. In-depth
in situ
&
ex situ
studies elucidate the mechanisms of action of the oligomers. This work demonstrates effective guidelines for future manufacturing.
The near-infrared (NIR) absorbing fused-ring electron acceptor, COi8DFIC, has demonstrated very good photovoltaic performance when combined with PTB7-Th as a donor in binary organic solar cells ...(OSCs). In this work, the NIR acceptor was added to state-of-the-art PBDBT-2F:IT4F-based solar cells as a third component, leading to (i) an efficiency increase of the ternary devices compared to the binary solar cells in the presence of the highly crystalline COi8DFIC acceptor and (ii) much-improved photostability under 1-sun illumination. The electron transport properties were investigated and revealed the origin of the enhanced device performance. Compared to the binary cells, the optimized ternary PBDBT-2F:COi8DFIC:IT4F blends exhibit improved electron transport properties in the presence of 10% COi8DFIC, which is attributed to improved COi8DFIC molecular packing. Furthermore, transient absorption spectroscopy revealed a slow recombination of charge carriers in the ternary blend. The improved electron transport properties were preserved in the ternary OSC upon aging, while in the binary devices they seriously deteriorated after simulated 1-sun illumination of 240 h. Our work demonstrates a simple approach to enhance both OSC efficiency and photostability.
Excess ammonium halides as composition additives are widely employed in perovskite light‐emitting diodes (PeLEDs), aiming to achieve high performance by controlling crystallinity and passivating ...defects. However, an in‐depth understanding of whether excess organoammonium components affect the film physical/electrical properties and the resultant device instability is still lacking. Here, the trade‐off between the performance and stability in high‐efficiency formamidinium lead iodide (FAPbI3)‐based PeLEDs with excess ammonium halides is pointed, and the underlying mechanism is explored. Systematic experimental and theoretical studies reveal that excess halide salt‐induced ion‐doping largely alters the PeLEDs properties (e.g., carrier injection, field‐dependent ion‐drifting, defect physics, and phase stability). A surface clean assisted cross‐linking strategy is demonstrated to eliminate the adverse impact of composition modulation and boost the operational stability without sacrificing the efficiency, achieving a high efficiency of 23.6%, a high radiance of 964 W sr−1 m−2 (The highest value for FAPbI3 based PeLEDs), and a prolong lifetime of 106.1 h at large direct current density (100 mA cm−2), concurrently. The findings uncovered an important link between excess halide salts and the device performance, providing a guideline for rational design of stable, bright, and high efficiency PeLEDs.
The component modulation‐induced ion doping of perovskite emitters and the underlying mechanism of the nature instability are revealed for FAPbI3‐based NIR PeLEDs with excess organic halides. By eliminating adverse effects of the excessively incorporated organoammonium halides using a surface clean‐assisted crosslinking strategy, a high efficiency of 23.6%, a high radiance of 964 W sr−1 m−2, and an excellent half‐lifetime of 106.1 h are achieved simultaneously.
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