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Ion doping is an effective strategy for achieving high‐performance flexible Cu2ZnSn(S,Se)4 (CZTSSe) solar cells by defect regulations. Here, a Li&Na co‐doped strategy is applied to synergistically regulate defects in CZTSSe bulks. The quality absorbers with the uniformly distributed Li and Na elements are obtained using the solution method, where the acetates (LiAc and NaAc) are as additives. The concentration of the harmful CuZn anti‐site defects is decreased by 8.13% after Li incorporation, and that of the benign NaZn defects is increased by 36.91% after Na incorporation. Synergistic Li&Na co‐doping enhances the carrier concentration and reduces the interfacial defects concentration by one order of magnitude. As a result, the flexible CZTSSe solar cell achieves a power conversion efficiency (PCE) of 10.53% with certified 10.12%. Because of the high PCE and the homogeneous property, the Li&Na co‐doped device is fabricated to a large area (2.38 cm2) and obtains 9.41% PCE. The co‐doping investigation to synergistically regulate defects provides a new perspective for efficient flexible CZTSSe solar cells. [ABSTRACT FROM AUTHOR]

The tandem organic solar cell could absorb the complementarity sunlight spectra by the sub-cells based on the different energy gap of the active-layer materials. In this work, a wide-band gap of the organic material PTB7-Th: PC71BM is used as the front sub-cells active layer, and the narrow-band gap of PTB7-Th: IEICO-4F is used as the rear sub-cells active layer. The front and rear sub-cells present the complementary absorption spectra leading to the sufficiently improvement of the sunlight absorption. MoO3/Au/ZnO multilayer film is the interconnecting layer. ZnO film was prepared by the sputtering method is smaller root-mean-square than that of the film prepared by the solution synthesis, resulting in a good contact interfacial between the sub-cells. This is in favor of the JSC and FF of the tandem organic solar cell. Importantly, the short-circuit current density of the tandem solar cell is handily controlled by the active-layer concentration of the front sub-cell, the tandem cell exhibits an optimal PCE of 11.77% with a large VOC of 1.45 V. [ABSTRACT FROM AUTHOR]

Flexible CZTSSe solar cells have attracted much attention due to their earth-abundant elements, high stability, and wide application prospects. However, the environmental problems caused by the high toxicity of the Cd in the buffer layers restrict the development of flexible CZTSSe solar cells. Herein, we develop a Cd-free flexible CZTSSe/ZnO solar cell. The influences of the ZnO films on device performances are investigated. The light absorption capacity of flexible CZTSSe solar cells is enhanced due to the removal of the CdS layer. The optimal thickness of the ZnO buffer layers and the appropriate annealing temperature of the CZTSSe/ZnO are 100 nm and 200 °C. Ultimately, the optimum flexible CZTSSe/ZnO device achieves an efficiency of 5.0%, which is the highest efficiency for flexible CZTSSe/ZnO solar cells. The systematic characterizations indicate that the flexible CZTSSe/ZnO solar cells based on the optimal conditions achieved quality heterojunction, low defect density and better charge transfer capability. This work provides a new strategy for the development of the environmentally friendly and low-cost flexible CZTSSe solar cells. [ABSTRACT FROM AUTHOR]

Antimony sulfide (Sb2S3) with a 1D molecular structure has strong bending characteristics, showing great application potential in flexible devices. Herein, the flexible substrate-structured Sb2S3 solar cells is developed and improve device performances by the back interface selenization. The high-quality Sb2S3 film with an optimal thickness of 1.8 μm, ensuring efficient spectra utilization, is deposited on flexible Mo foils by the rapid thermal evaporation technique. To solve the issues of back interfacial recombination and charge transport, the 20 nm MoSe2 layer between Sb2S3 film and Mo foil is fabricated by substrate selenization in the tube furnace. Further investigations indicate that the MoSe2 layer improves the interfacial energy band alignments and induces the [hk1] orientation of Sb2S3 film, thereby passivating defects and enhancing the carrier transport capacity. The flexible solar cell in the structure of Mo foil/MoSe2/Sb2S3/CdS/ITO/Ag, exhibiting good flexibility to stand thousands of bending, achieves an efficiency of 3.75%, which is the highest for Sb2S3 devices in substrate configuration. The presented flexible structure and back interfacial selenization study will provide new prospects for inorganic Sb2S3 thin film solar cells. [ABSTRACT FROM AUTHOR]

Flexible Cu2ZnSn(S, Se)4 (CZTSSe) solar cells have the advantages of nontoxicity and low cost, showing great commercial potential in wearable devices, indoor photovoltaics, and building‐integrated photovoltaics. Currently, the performances of flexible CZTSSe devices still faces a huge gap on the commercialization level. Herein, the development of flexible CZTSSe devices to provide the challenges is summarized and possible strategies are explored. During the past ten years of research, flexible CZTSSe devices' efficiency has increased to 11.19% through studies of flexible substrates, residual stress, deposition processes, and physics. However, the improvement of efficiency is facing large challenges in severe open‐circuit voltage loss and low fill factor. After solving the issues by the strategies of deep‐level defect passivation and interface optimization, the efficiency of flexible CZTSSe solar cells is expected to reach the commercial level. [ABSTRACT FROM AUTHOR]

The buffer layer plays a critical role in high‐performance flexible Cu2ZnSn(S,Se)4 (CZTSSe) solar cell. The conventional CdS buffer layer causes the photoelectric performance loss and the pollution of toxic Cd. Herein, the ultrathin CdS and Zn0.8Sn0.2O (ZTO) buffer layer engineering is proposed to reduce interface recombination and Cd content. An ultrathin CdS layer acts as the interface passivation layer to protect the CZTSSe layer and passivate its surface defects. To solve the problems of decreased carrier collection capacity caused by thinning the CdS layer, the ZTO layer with low resistivity and high carrier concentration is obtained by doping Sn into the ZnO layer. The systematic study indicates that the ultrathin CdS and ZTO buffer layers‐based solar cells realize high‐quality interface and band matching. Ultimately, 9.3% efficiency of the ultrathin CdS and ZTO‐based solar cell with 448 mV open‐circuit voltage is obtained, which is higher than that of the standard CdS buffer layer‐based device (8.5% with 419 mV). The study provides a new idea for achieving efficient flexible CZTSSe solar cells through heterojunction interface management. [ABSTRACT FROM AUTHOR]

Summary: In recent years, the laser half‐cutting technology for silicon solar cells has gotten much attention from researchers for increasing module power and would become particularly important in the photovoltaic modules domain. Herein, this paper would introduce a kind of new laser cutting process, a thermal laser separation (TLS) cutting technology. In the laser cutting processes, the influence on mechanical and electrical characteristics of bifacial p‐type passivated emitter and rear (PERC) solar cell and module were investigated in considerable detail. We have made a series of research and analyses including the cutting principle, opening length, fracture surface, and hot influence zone. The results reveal that the TLS cutting process could reduce damage more than the regular laser scribing and cleaving (LSC) cutting process. The TLS cutting process would achieve the higher power of a PERC half‐cutting bifacial module and the stronger bending strength of half solar cells than the LSC cutting process. [ABSTRACT FROM AUTHOR]

Sb2S3 has emerged as a promising light‐absorbing material due to its nontoxicity, low cost, high stability, and absorption coefficient. However, the absorption spectrum ranges and back‐contact barrier between Sb2S3 and Au strongly limit the device performance. p‐type Sb2Se3 has a similar lattice structure and properties as Sb2S3, obtaining absorption expansion and ohmic back contact. Herein, efficient all‐inorganic planar Sb2S3 solar cells with the addition of Sb2Se3 layers are fabricated. The functions of Sb2Se3 as cooperative absorber (400 nm) and hole transport layers (HTL, 80 nm) are further explored. Systematic characterizations indicate that the junction quality and depletion widths of the device with the addition of Sb2Se3 are improved by forming a p–i–n structure. As a result, the all‐inorganic Sb2S3 solar cell with a Sb2Se3 HTL greatly increases the power conversion efficiency from 2.7% to 5.8% and the fill factor from 40% to 55.4%. The additional Sb2Se3/Au interface with matched energy‐level alignments reduces the back‐contact barrier and facilitates hole transport and collection. The present design and methods promote the development of Sb2S3 solar cells. [ABSTRACT FROM AUTHOR]

Triplet excitons have both longer lifetimes and diffusion lengths than singlet excitons due to the nature of triplet excitons, which is expected to increase the photocurrent and further improve the performance of organic solar cells (OSCs). However, the working mechanism of triplet excitons in OSCs is not clearly clarified. Therefore, it is urgent to develop new triplet acceptors for in‐depth understanding. Herein, a series of acceptors (BTn‐4Cl) are synthesized by fine‐tuning of the side‐chain branch positions. The generation of triplet excitons of BTn‐4Cl is confirmed by the time‐resolved photoluminescence (TRPL) spectra, magnetophotocurrent (MPC) experiment, and electron paramagnetic resonance (EPR) spectra. The effects of side‐chain engineering on the optoelectronic properties, packing behaviors, energy losses, charge transport properties, spin lifetimes of triplet polarons, and blend film morphologies are systematically studied. These results show that D18:BT3‐4Cl‐based OSCs possess the best power conversion efficiency (PCE) of 17.31% due to lower energy losses, less recombination losses, more balanced charge carrier mobilities, longer spin–lattice (T1) relaxation time, and more favorable morphology. This work enhances the understanding of the structure–property relationship for high‐performance triplet acceptors. [ABSTRACT FROM AUTHOR]

A unique feature of nonfullerene acceptors (NFAs) is their strong photoabsorption capability at longer wavelengths and electrostatic potentials (ESPs), which is expected to increase the photocurrent density (J) for bulk heterojunction (BHJ)‐based semitransparent organic solar cells (ST‐OSCs). Indeed, the interior spin‐optoelectronic phenomena are incredibly rich, and it remains challenging to correlate them with a complete photovoltaic process. Here, a prototypical PTB7‐Th: IEICO‐4F‐based ST‐OSC, with an average visible transmittance (AVT) of ≈26.8%, is fabricated for studying the issue (PTB7‐Th: poly[4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b;4,5‐b′]dithiophene‐2,6‐diyl‐alt‐(4‐(2‐ethylhexyl)‐3‐fluorothieno[3,4‐b]thiophene‐)‐2‐carboxylate‐2‐6‐diyl)]; IEICO‐4F: 2,2′‐((2Z,2′Z)‐(((4,4,9,9‐tetrakis(4‐hexylphenyl)‐4,9‐dihydro‐sindaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis(4‐((2‐ethylhexyl)oxy)thiophene‐5,2‐diyl))bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile). Spin‐dependent electron–hole dissociation and charge transport dynamics are systematically studied in the dark condition, the short‐circuit current density (Jsc) condition, and some intermediate stages by the nondestructive in situ magnetophotocurrent (magneto‐J) technique. Some intriguing mechanisms such as the Coulomb blockade–based bipolaron, the spin‐dependent polaron pair dissociation at charge transfer states (CTSs), and the triplet‐polaron reaction are extensively explored in the study. Despite these, the monochromatic light‐induced polarizability is validated to have a remarkable impact on the magnitude of the open circuit voltage (Voc). This work is completely devoted to the spin‐optoelectronic phenomena of the NFA‐based ST‐OSC in working condition. [ABSTRACT FROM AUTHOR]

A desirable driving force or dissociation energy greater than 0.300 eV is thought to be the prerequisite for an efficient dissociation of exciton in the organic bulk heterojunction photovoltaic system. This criterion has confronted the challenge in some nonfullerene acceptors (NFAs) based solar cells. Factors that govern the dissociation are still under debate. In this work, it is demonstrated that a large photocurrent can be produced by a NFA organic blend with a negligible driving force (0.070 eV) and a small dielectric constant (ε = 4). By evaluating the magnetic field dependent photocurrent density and photoluminescence, we postulate that the spin-dependent polaron pair dissociation at charge transfer states due to a significant singlet generation may prove critical for the photocurrent production. The driving force that originates from the energy offset may play a negligible role in the exciton dissociation. [ABSTRACT FROM AUTHOR]

Environment-friendly flexible Cu2ZnSn(S,Se)4 (CZTSSe) solar cells show great potentials for indoor photovoltaic market. Indoor lighting is weak and multi-directional, thus the researches of photovoltaic device structures, techniques and performances face new challenges. Here, we design symmetrical bifacial CZTSSe solar cells on flexible Mo-foil substrate to efficiently harvest the indoor energy. Such devices are fabricated by double-sided deposition techniques to ensure bifacial consistency and save cost. We report 9.3% and 9% efficiencies for the front and back sides of the flexible CZTSSe solar cell under the standard sun light. Considering the indoor environment, we verify weak-light response performance of the devices under LED illumination and flexibility properties after thousands of bending. Bifacial CZTSSe solar cells in parallel achieve the superposition of double-sided output current from multi-directional light, significantly enhancing the area utilization rate. The present results and methods are expected to expand indoor photovoltaic applications. Indoor lighting is weak and multi-directional, thus the requirement for photovoltaic differs from that designed for outdoor. To efficiently harvest the indoor energy, the authors designed CZTSSe bifacial solar cells on flexible Mo substrate using double-sided deposition to ensure consistency and to save cost. [ABSTRACT FROM AUTHOR]

Abstract Sb 2 Se 3− x S x is considered a promising absorber material for solar cell applications because of its tunable band gap. However, theoretical research on Sb 2 Se 3− x S x is still limited. In this research, the crystal structure, electronic structure and photoelectric properties of Sb 2 Se 3− x S x (x = 0 , 0.125, 0.25, 0.5, 0.75) were determined using first-principles calculations based on density functional theory. The band gap is affected by the structural distortion and covalence of Sb 2 Se 3− x S x with increasing S concentration. From x = 0 to x = 0.75 , the covalence of Sb 2 Se 3− x S x gradually increases. While for x = 0.125 and x = 0.25 , the structural distortion are more severe than the others. Combining with the affects of both, the band gap decreases first and then increases with increasing S concentration. By calculating the carrier effective masses and optical characteristics of Sb 2 Se 3− x S x , it can be found that Sb 2 Se 3− x S x (x = 0.5) shows the optimized photoelectric properties. The results provide some guidance for the further development of Sb 2 Se 3− x S x solar cells by adjusting band gap. Graphical abstract The band gap of Sb 2 Se 3− x S x decreases first and then increases with S concentration, and Sb 2 Se 3− x S x (x = 0.5) possesses the optimized photoelectric properties. fx1 Highlights • The band gap of Sb 2 Se 3− x S x decreases first and then increases with S concentration. • Band gap change is affected by the structural distortion and covalence of Sb 2 Se 3− x S x. • The carrier effective mass of Sb 2 Se 3− x S x (x = 0.5) is the smallest. • Sb 2 Se 3− x S x (x = 0.5) has the optimized photoelectric properties as absorber material. [ABSTRACT FROM AUTHOR]

In this paper, we report one bifacial p-type PERC solar cell with efficiency over 22% using laser doped selective emitter produced in larger-scale commercial line on 6-inch mono-crystalline wafer. On front side of the solar cell, square resistance of p-n junction was found to be closely related with laser power at certain laser scan speed and frequency. On the other side, the rear fingers with different ratios of height and width and rear silicon nitride (SiNx) layer with different thickness were optimized, and a highest rear efficiency of the bifacial solar cell was obtained. Finally, bifacial silicon solar cells with the front and rear efficiencies exceeding 22% and 15% (AM1.5, 1000 W/m2, 25 °C) were successfully achieved, respectively. [ABSTRACT FROM AUTHOR]

Partial cation substitution is an effective way to inhibit defects and carrier recombination, which can improve the efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. Herein, flexible Cu2Zn1−xCdxSn(S,Se)4 (x = 0–15%) solar cells are fabricated on Mo foils with partial Cd substitution for Zn via a green solution‐process. The best device performance can be achieved when Cd/(Zn + Cd) = 8%, with an efficiency up to 6.49% and a significantly improved device repeatability. The EU decreases from 24 to 15 meV, indicating that antisite defects and band tailings are effectively suppressed. C–V data reveal that Wd and Vbi are enhanced after doping Cd, resulting in a stronger built‐in electric field which facilitates Fermi‐level splitting and hence increases band bending of the absorber toward the junction interface. Furthermore, the mechanism of current shunting is studied using an equivalent circuit model with three parallel current pathways to fit J–V curves. The key parameters for the solar cell diode such as A, J0, and Rsh are significantly improved by partially substituting Zn with Cd, demonstrating that current shunting loss is suppressed and the junction quality is improved, resulting in a significant improvement in device repeatability. [ABSTRACT FROM AUTHOR]

A nonfullerene acceptor (NFA), named 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′] dithiophene (ITIC) with the fused aromatic conjugated backbone structure, is an intriguing small molecular semiconductor in the application of organic bulk heterojunction (BHJ) solar cells. However, the underlying spin‐dependent photo‐physics in the photovoltaic process remains deficient. Here, ITIC‐based thin solid film, binary, and ternary organic blends are designed and fabricated with two polymeric donors, poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]‐dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))] (PBDB‐T) and poly[(2,6‐(4,8‐Bis(3‐((2‐ethylhexyl)oxy)‐phenyl)‐benzo[1,2‐b:4,5‐b′]‐dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))] (PBPD‐Th). With the spin‐sensitive magneto‐photocurrent and magneto‐electroluminescence measurements, ITIC always exhibits large magnetic field effects with negative signs in the ambient temperature. The effect is attributed to the exciton‐charge reaction. However, both positive and negative signs are detected in the binary and ternary organic blends at small and large fields, respectively. The results elucidate that the mutual combination of the spin‐dependent polaron pair dissociation and exciton‐charge reaction plays a decisive role in the photovoltaic process. Furthermore, with photo‐induced electron paramagnetic resonance (EPR) studies, the full width at half maximum (FWHM) of the line shape for the positive magneto‐photocurrent is firmly associated to the magnitude of the effective g‐factor. The present study may shed a new light on the deep understanding of spin‐dependent photo‐physical process in NFA‐based solar cells for organic opto‐spintronic developments. [ABSTRACT FROM AUTHOR]

Perovskite solar cells have gradually become the most attractive alternative for next-generation photovoltaic devices due to their excellent photovoltaic conversion efficiencies and low manufacturing costs. Defect engineering is an essential topic for improving the performance of perovskite devices. In this study, we utilize a bifunctional alkylamine sulfonate to modify the perovskite interfaces. The TsO− of sulfonates coordinates with Pb2+, while –NH 2 of alkylamine forms hydrogen bonds with iodine, which reduces charge recombination and improves energy level arrangement. The molecular size and the alkylamine's dielectric constant significantly influence the interface modification performance. For the champion device with BATsO treatment, there is an enhancement in both the fill factor and the open-circuit voltage, resulting in a power conversion efficiency (PCE) of 23.53%. After 400 h of working condition, the device maintains roughly 90.40% of its initial efficiency. Therefore, this study postulates that modifying bifunctional alkylamine sulfonates could effectively enhance the PSC's performance. • Diverse alkylamine sulfonates were used in PSCs to study cationic alkyl' impact on interface passivation. • Sulfonates' TsO− coordinates with Pb2+, while alkylamine's –NH 3 + forms bonds with iodine, enhancing energy level order. • PSCs treated with BATsO achieved the best efficiency of 23.53%. [ABSTRACT FROM AUTHOR]

[Display omitted] • A 17.71% PCE is achieved in ternary OSCs with 100 nm thick active layer. • The ternary OSCs have good thickness-tolerance, benefiting for mass production. • Providing new viewpoint for understanding performance improvement of OSCs. Ternary-blend organic solar cells (TOSCs) are fabricated with PM6:BTP-4F-12 as the host system and IT-M as the third component. The third component IT-M takes multiple roles in improving performance of TOSCs through reducing energy-loss of the optimized TOSCs, optimizing molecular arrangement and phase separation in active-layers. The well optimized molecular arrangement and phase separation can be beneficial to charge separation and transport in TOSC, which can be confirmed by the characterization of 2D grazing incidence wide-angle X-ray scattering, transmission electron microscopy, magneto-photocurrent, as well as electrochemical impedance spectroscopy. By finely optimizing IT-M content, a power-conversion-efficiency (PCE) of 17.71% is achieved in the optimized TOSCs, benefiting from simultaneously enhanced short-circuit-current density (J SC) of 25.95 mA cm−2, open-circuit-voltage (V OC) of 0.875 V and fill-factor (FF) of 78.02% in comparison with the OSCs with PM6:BTP-4F-12 as active-layers. Furthermore, average PCE over 15% can be achieved from twenty individual TOSCs with active-layer thickness of 300 nm, indicating the optimized TOSCs have excellent thickness tolerance. [ABSTRACT FROM AUTHOR]