Average Power Conversion Efficiency Research Articles

Understanding the optoelectronic and vibrational properties of MB[formula omitted]O[formula omitted], using density functional theory, where M = Yb or Ce

This work aims to use density functional theory (DFT) and density functional perturbation theory (DFPT) to study the structure, optoelectronics, phonon dispersion and energetic stability of two new tetraborates, MB4O7, where M = Yb or Ce. The estimated values of the band gap energy (Eg) and power conversion efficiency (PCE) for the systems were calculated. The Shockley-Queisser was also taken into account to measure the maximum theoretical efficiency of a photovoltaic source cell based on a p-n union. The estimated average gap energy values for the YbB4O7 and CeB4O7 systems, calculated using the GGA-PBE, HSE06, and GGA+U functionals, were 3.64 eV and 0.97 eV, respectively. The average PCEs calculated for the YbB4O7 and CeB4O7 systems were 11.28% and 25.66%, respectively. The PCE and energy stability suggest that CeB4O7 may be a more viable candidate for a solar device than YbB4O7, at least in terms of these specific parameters. The results reported here, as well as those related to absorption calculations, showed that the structures have optical responses in the visible region, suggesting that both systems can be used as optoelectronic devices and in solar cell designs.

Enhance the Performance of CZTSSe Solar Cells Through Inhibiting the Cu2+, Tu, and (─COOH) Association Reaction.

The Sol-gel precursor solution reaction mechanism has a significant impact on the Cu2ZnSn(S, Se)4 (CZTSSe) solar cells. It is discovered that in the Cu2ZnSnS4 (CZTS) precursor solution (CZTS-PS) in the preparation, there is an association reaction among Cu2+, thiourea (Tu), and carboxyl (-COOH), which is an important reason for the undesirable CZTSSe solar cells. The strong association reaction generates excessive Cu2+ ions, forming the CuxSe secondary phase on the surface of the CZTSSe absorber. The secondary phase causes a short circuit and deterioration of gadget performance. Following a 6-h aging period for the CZTS-PS, the average photoelectric conversion efficiency (PCE) of the device is enhanced to 8.02%, and there is also an improvement in device uniformity, as evidenced by a decrease in the standard deviation to less than 1. To inhibit the association reaction and eliminate the aging time phenomenon, a strategy is developed using hydrochloric acid to regulate the CZTS-PS environment. This strategy shifts the REDOX reaction in Cu2++Sn2+ toward the formation of Cu1++Sn4+, leading to a decrease in the defect concentrations of VSn(-/0) and CuSn(-/0), which increases the carrier concentration and reduces the impact of band tailing. The average power conversion efficiency (PCE) of the devices improved from 7.45% to 9.26%, the PCE of the best-performing CZTSSe solar cells increased from 9.25% to 9.83%, and the consistency among the devices is further enhanced, as indicated by a reduction in the standard deviation from 0.98 to 0.44. Ultimately, the device performance of the Cu2++Sn2+-DMF system improved by 11.01% (without the MgF2 layer) after optimization. This study serves as a reference for regulating the environment of the CZTS-PS to further enhance the CZTSSe devices' performance, and the photoelectric conversion efficiency is improved by ≈30%.

Correlation between Photoluminescence Features and Enhanced Performance in Formamidinium Lead Triiodide Quantum Dot Solar Cells by Replacement of Octadecene

In this study, an innovative approach is developed for fabricating formamidinium lead triiodide (FAPbI3) quantum dots (QDs) by substitution of octadecene (ODE). The results showcase the formation of superior‐quality FAPbI3 QD films, boasting enhanced photoluminescence (PL) and transport properties. Specifically, ODE has been replaced with octene (OCE), a shorter linear alpha olefin. Comparisons are drawn between the novel synthesis method and the conventional ODE‐based QD films, scrutinizing their optical properties and applicability in QD solar cells. The outcomes highlight distinctions in temperature‐dependent PL emission characteristics, revealing an unprecedented absolute PL QY of up to 84%, a notable improvement from the 70% achieved with ODE, along with enhanced transport properties. Furthermore, the performance of both systems in QD solar cells is evaluated for two values of layer thickness, 100 and 200 nm, to investigate the transport properties at the device level. The results exhibit a remarkable improvement from 200% to 150% in average power conversion efficiency (PCE) and consistently higher values for open‐circuit voltage and short‐circuit current density for the OCE‐based solar cell compared to an ODE‐based counterpart for both thickness values, reaching a striking 6.7% PCE for the best‐performing device despite the nonideal conditions.

Scaling Up Perovskite Solar Cell Fabrication: Antisolvent‐Controlled Crystallization of Printed Perovskite Semiconductor

Scaling up perovskite solar cells stands as one of the frontiers in advancing this rapidly growing technology. Yet, controlling perovskite thin‐film crystallization during and post‐printing differs significantly from lab‐scale processes that have yielded record device efficiencies. This study investigates antisolvent treatment for slot‐die‐coated perovskite solar cells using in situ optical spectroscopy and comparing among multiple antisolvents. The antisolvent bath used in slot‐die coating affects the perovskite crystallization and film quality differently when comparing to the established spin‐coating antisolvent treatment process. A novel dynamic antisolvent method, employing either vortex or laminar flow, is developed. It outperforms steady‐bath techniques in generating high‐quality, haze‐free films. Optimization studies identify critical treatment times. Implementing this novel antisolvent treatment leads to a peak average power conversion efficiency of 15.62% and the highest device efficiency of 18.57%, an excellent performance for slot‐die‐coated MAPbI3 devices printed and tested under ambient conditions. The method is validated for an alternative perovskite composition, FA0.9Cs0.1PbI3, and printing technique, blade coating. This research highlights the importance of in situ analysis for enhancing perovskite film quality and introduces scalable approaches for controlling large‐area film crystallization kinetics, driven by the demand for efficient and scalable manufacturing processes in the field of perovskite solar cells.

Enhancing Light Utilization Efficiency of Semi‐Transparent Perovskite Solar Cells via Tailored Interfacial Engineering

AbstractSemi‐transparent perovskite solar cells (ST‐PSCs) are promising for their application in building integrated photovoltaics (BIPVs). For BIPVs, a light utilization efficiency (LUE) > 2.5 is required which is multiplication of average visible transmittance (AVT) and power conversion efficiency (PCE). Generally, semitransparency is achieved by reducing film thickness which increases AVT but decreases PCE resulting in lower LUE. Here, an interface engineering strategy is employed on a wide bandgap perovskite thin absorber layer to increase PCE and LUE. The study employs three different alkylamine hydrochlorides molecules with varied alkyl chain length, viz., 2‐chloroethylamine‐hydrochloride, 3‐chloropropylamine‐hydrochloride, and 4‐chlorobutyalamine‐hydrochloride at perovskite/electron transport layer (ETL) interface and investigates their effect on perovskite crystallization. Further, it is demonstrated that 4‐chlorobutyalamine‐hydrochloride can strongly interact with perovskite and suppress non‐radiative recombination facilitating charge transport at the perovskite/ETL interface. Devices post‐treated with 4‐chlorobutyalamine‐hydrochloride interfacial layer, demonstrate a higher LUE of 3.45% (PCE 14.11%) and AVT of ≈25% (400–800 nm), with Voc of 1.23 V. Moreover, the unencapsulated devices retain ≈89% of the initial efficiency after storage for 1500 h under a relative humidity of ≈35–40%. This study provides an efficient approach to improve LUE and stability of ST‐PSCs for the application in energy‐efficient smart windows.

High-performance semi-transparent organic solar cells for window applications using MoO3/Ag/MoO3 transparent anodes

The optimization of semi-transparent organic solar cells involves balancing average visible transparency (AVT) and power conversion efficiency (PCE). We propose enhancing ST-OSC performance by replacing the conventional opaque Ag electrode with a MoO3/Ag/MoO3 as a dielectric/metal/dielectric (DMD) layer structure, explored theoretically and experimentally. A prototype ST-OSC configuration, comprising ITO/ZnO/P3HT: PCBM/MoO3/Ag/MoO3, was fabricated with varying thicknesses of the MoO3/Ag/MoO3 layer, determined through theoretical calculations utilizing MATLAB software. This study investigates the impact of metal layer thickness on two active layer densities (10 and 18 mg/mL) and evaluates AVT, color rendering index, Correlated Color Temperature, and CIELAB color coordinates (a*, b*). Both theoretical calculations and experimental results confirm that the optimized configuration of the DMD structure with specific layer thicknesses for each component (MoO3 = 10nm/Ag = 6nm/MoO3 = 30 nm) achieves an AVT of over 59.60 %. This high level of transparency makes this configuration suitable for applications requiring both high transparency and efficient light transmission. The optimized device delivered high-quality light transmission, approaching white perception to the human eye. This combined approach validates empirical results and provides a deeper understanding of transparent OSC mechanisms.

Photovoltaic enhancement in OSCs based on PM6:Y7 when doping the active layer with Ag2S nanoparticles

Herein, silver sulfide (Ag2S) nanoparticles (NPs) with an average size of 31 nm ± 4 nm were synthesized using a simple, economic, and eco-friendly method assisted by ultrasonic bathing; the reaction was carried out in a non-polluting aqueous medium. These Ag2S NPs were suspended in ethanol and used to dope the active layer of Organic Solar Cells (OSCs) based on PM6 (donor) and Y7 (acceptor) by adding 2 v/v % of a suspension to the PM6:Y7 solution in chlorobenzene (CB). The entire fabrication process and testing was carried out under normal atmospheric conditions. Field's metal (FM) was used as the top electrode of the OSCs, which is a eutectic alloy of bismuth, indium, and tin (Bi 32.5 %, In 51 %, and Sn 16.5 %) with a melting point above 62 °C deposited by free evaporation techniques. The average Power Conversion Efficiency (PCE) for the reference and doped OSCs were 9.19 % (9.43 % the best) and 10.31 % (10.77 % the best), respectively; representing an increase of more than 14 % in the PCE value when Ag2S NPs are added to the active layer. It can be attributed to different optical phenomena, among which could be the enhance in the internal light reflection processes (scattering) and the Local Surface Plasmon Resonance (LSPR) effect.

Facet orientation control of tin-lead perovskite for efficient all-perovskite tandem solar cells

Developing high-performance narrow-bandgap (NBG) perovskite solar cells based on tin-lead (Sn-Pb) perovskite is critical for the advancement of all-perovskite tandem solar cells. However, the limitations of the device current density and efficiency are magnified by the issues concerning poor carrier transport caused by a substantial number of defects in thick NBG films. This problem is further exacerbated by the quality of film crystallization, which is associated with the rapid and uncontrolled crystallization of Sn-rich perovskite chemistry using the antisolvent approach. We regulate the crystallization of Sn-contained perovskite with a mild gas-quench approach to fabricate a highly crystal-oriented and well-arranged NBG perovskite absorber. This strategy effectively boosts electron transport and light absorption of the NBG perovskite. Consequently, the average power conversion efficiency (PCE) of the NBG perovskite solar cells increases from 19.50 % to 21.18 %, with the best device achieving an excellent PCE of 21.84 %. Furthermore, when combined with a wide-bandgap perovskite subcell to form an all-perovskite tandem solar cell, a PCE of 25.23 % is achieved. After being stored in the glovebox for 1000 h, the unencapsulated device maintains over 90 % of its initial PCE, demonstrating long-term stability and durability. This work presents a promising approach for developing high-efficiency NBG perovskite solar cells.

Moisture‐Induced High‐Quality Perovskite Film in Air for Efficient Solar Cells

The quality of perovskite light‐harvesting layer is known to be the most critical factor for the performance of perovskite solar cells (PSCs). Herein, a facile ambient air‐aging process (AAP, 20%–30% RH) is adopted to realize the fabrication of high‐quality Cs0.15FA0.75MA0.1PbI3 perovskite films, thereby upgrading device performance. We find that the perovskite crystallinity after AAP for 10 d is greatly intensified, with large grain size and preferred crystal orientation along (110) and (220) planes. Comparative studies on the Ag‐based devices employing the perovskite films upon exposing to different atmospheres, i.e., dry N2, dry O2, N2, and H2O (20%–30% RH) and ambient air (20%–30% RH), demonstrate that H2O molecules in air rather than O2 molecules induce an effective defect passivation that holds the multiple functions in enhancing the quality of perovskite film, inhibiting the nonradiative recombination, prolonging the carrier lifetime, and improving the energy level matching, etc. Moreover, the positive effect of H2O in ambient atmosphere on cell performance is irreversible and remains even if moisture escapes. Finally, the average power conversion efficiency (PCE) of device based on the AAP‐induced film is increased from 18.24 ± 1.49 to 21.34 ± 0.76, with the champion PCE up to 22.60%. Also, the device with AAP exhibits better moisture resistance capability. Herein, it offers a viable AAP‐induced route for the perovskite films with superb optoelectronic properties that can be subsequently extended to the design and construction of other photovoltaic devices for practical application.

High‐Quality Additive‐Free α‐FAPbI3 Film Fabricated by Alkane/Nanocrystals Method and Surface Chemistry Modulation for Efficient Perovskite Solar Cell

AbstractIt's still a scientific issue to synthesize exotic amines‐free and pure‐phase FAPbI3 film because most FAPbI3 films are synthesized by adding MACl‐like exotic amines salts in their precursor solution to reduce the phase transition barrier. In this work, high‐quality and additive‐free phase‐pure α‐FAPbI3 films are successfully fabricated via the sustainable Alkane/Nanocrystals method. FAPbI3 nanocrystals (NCs) are performed as the heterogeneous nuclei to promote the nucleation and crystallization of FAPbI3 films. Cryogenic‐TEM and in situ GIWAXS evidence the seed function and interesting phase evolution of FAPbI3 NCs. The whole phase transition course of pure FAPbI3 film is systematically studied. IR‐AFM and ToF‐SIMS reveal ligands capped on NCs are extruded to the film surface. PbAc‐IPA solution treating the film surface can effectively wash off the surplus ligands at the surface and modulate the surface chemistry and energy levels. As a result, an average power conversion efficiency (PCE) of 21.45% is achieved for MA‐free pure α‐FAPbI3 perovskite solar cells (PSCs), as well as the best light‐soaking stability record of retaining 95% of the initial PCE after 800 h. This work paves a new way to fabricate MA‐free pure α‐FAPbI3 PSCs.

Design Principles of Diketopyrrolopyrrole‐Thienopyrrolodione Acceptor1–Acceptor2 Copolymers

AbstractThe design principles of acceptor1–acceptor2 copolymers featuring alternating diketopyrrolopyrrole (DPP) and thienopyrrolodione (TPD) moieties are investigated. The investigated series of polymers is obtained by varying the aromatic linker between the two acceptor motifs between thiophene, thiazole, pyridine, and benzene. High electron affinities between 3.96 and 4.42 eV, facilitated by the synergy of the acceptor motifs are determined with optical gaps between 1.37 and 2.02 eV. Grazing incidence wide‐angle X‐ray scattering studies reveal a range of film morphologies after thermal annealing, including face‐on, end‐on and superstructure edge‐on‐like crystallites. Conversely, all materials form thin edge‐on layers on the polymer–air interface, as demonstrated by multi‐elemental near‐edge X‐ray absorption fine‐structure spectroscopy. The benefit of the electron‐deficient linkers thiazole and pyridine is evident: In organic field effect transistors, electron mobilities of up to 4.6 × 10−2 cm2 V−1 s−1 are obtained with outstanding on/off current ratios of 5 × 105, facilitated by the absence of detectable hole transport in these materials. Viability for all‐polymer solar cells is assessed in active layer blends with the donor polymer PM6, yielding a maximum average power conversion efficiency of 4.8% and an open circuit voltage above 1 V.

Thermal management of PV based on latent energy storage of composite phase change material: A system-level analysis with pore-scale model

Perovskite Solar Cell (PSC) have recently emerged as exciting new candidates of Photovatics (PVs) for solar-to-electrical energy conversion. Nevertheless, one huge obstacle to its commercialization is how to improve its tolerance to operation at elevated temperatures. To address this issue, Composite Phase Change Material (CPCM) incorporated with a porous skeleton structure is proposed to integrate with PVs. In this structure, an important theoretical problem is that the temperature dependence of PV and the temperature control behavior of CPCMs interact with each other (bidirectional relationship). In this work, a pore-scale lattice Boltzmann phase change model is established to describe the dynamic thermal behavior of CPCMs and explore the roles of the bidirectional relationship between PVs and CPCMs, the change of power conversion efficiency influenced by temperature variation and glass transmissivity is discussed by comparing the overall liquid fraction of CPCMs, and the average temperature and power conversion efficiency of PVs. Furthermore, the situation of time-varying solar irradiation is discussed to mimic real application conditions. Results indicate that the neglecting temperature dependency of PVs leads to underestimation of PV surface temperatures and overestimation of power conversion efficiencies, while glass transmissivity provides reverse effects. These phenomena not only happen in constant solar irradiation but also in varying solar irradiation, calling for increasing attention to designing PV/CPCMs for varying heat flux conditions. The findings of this work establish a comprehensive manner toward integrated design of CPCMs for PV thermal control.

Optically Enhanced Semitransparent Organic Solar Cells with Light Utilization Efficiency Surpassing 5.5%

AbstractConverting non‐visual light into photocurrent while maintaining high visual transparency is vital for semitransparent organic solar cells (ST‐OSCs) application, yet often challenging over insufficient invisible light‐harvesting. Herein, spectrally selective optical manipulation for ST‐OSCs with high visual light transparency and full‐spectral non‐visual light reflection is proposed by matching the optical admittance of ultrathin Ag films using ZnS and MgF2. The reflection of optically enhanced ST‐OSCs at the spectral region beyond the human eye's response spectrum is improved and the transmission in the visual region is simultaneously enhanced. By further integrating an anti‐reflective structure, the optimal structure boosts the average visible transmittance and power conversion efficiency of ST‐OSCs to 44.3% and 12.6%, respectively, yielding a record light utilization efficiency of 5.6%. Corresponding flexible ST‐OSCs with high mechanical stability implies that this work provides a facile and universal strategy for ST‐OSCs aiming at building integrated photovoltaics.

L‐Arginine‐Doped PFN‐Br as a Cathode Interlayer for Conventional Organic Solar Cells

The cathode interlayer (CIL) plays a crucial role in organic solar cells (OSCs), which can establish an Ohmic contact between the active layer and the electrode, lower the electron extraction barriers, and minimize the charge carrier recombination. The CIL modification is a useful strategy for improving the performance of OSCs. Herein, an inexpensive water–alcohol‐soluble material known as L‐Arginine (L‐Arg) is introduced as a modifier for the PFN‐Br CIL, leading to successful optimization of the CIL quality. Following L‐Arg modification, the work function of the CIL is lowered and the electron extraction is facilitated. L‐Arg assists in exciton dissociation while suppressing both bimolecular and trap‐assisted recombination processes. The modified CIL establishes superior contact with the metal electrode due to its enhanced hydrophilicity, which helps electron collection. Consequently, the average power conversion efficiency increases from 10.54% in the reference device to 11.17% in the optimally doped device.

Designed Mesoporous Architecture by 10–100 nm TiO2 as Electron Transport Materials in Carbon-Based Multiporous-Layered-Electrode Perovskite Solar Cells

Fully printable carbon-based multiporous-layered-electrode perovskite solar cells (MPLE-PSCs) are easy to fabricate and have excellent durability. In this study, the porosity of the mesoporous TiO2 layer as the electron transport layer in MPLE-PSCs was controlled by varying the particle diameter of TiO2 nanoparticles from 14 nm to 98 nm. Furthermore, the results of absorbed photon-to-current conversion efficiency, visible light reflectance spectroscopy, pore-size distribution, X-ray diffraction, field emission scanning electron microscopy, and photovoltaic parameters of MPLE-PSCs are discussed. Although the porous TiO2 layer with smaller nanoparticles showed higher photoabsorption, it was found that the more voids of perovskite crystals created in the TiO2 porous layer, the smaller the particle size (<18 nm). The porous TiO2 layers with particles over 26 nm are well filled with perovskite crystals, resulting in a higher photovoltaic capacity with TiO2 particles over 26 nm. As a result, the short-circuit current density (JSC) showed a maximum value using 43 nm TiO2 particles, with an average power conversion efficiency (PCE) of 10.56 ± 1.42%. Moreover, the PCE showed a maximum value of 12.20% by using 26 nm TiO2 nanoparticles.

Understanding and Mitigating Atomic Oxygen-Induced Degradation of Perovskite Solar Cells for Near-Earth Space Applications.

Combining high efficiency with good radiation tolerance, perovskite solar cells (PSCs) are promising candidates to upend expanding space photovoltaic (PV) technologies. Successful employment in a Near-Earth space environment, however, requires high resistance against atomic oxygen (AtOx). This work unravels AtOx-induced degradation mechanisms of PSCs with and without phenethylammonium iodide (PEAI) based 2D-passivation and investigates the applicability of ultrathin silicon oxide (SiO) encapsulation as AtOx barrier. AtOx exposure for 2h degraded the average power conversion efficiency (PCE) of devices without barrier encapsulation by 40% and 43% (w/o and with 2D-PEAI-passivation) of their initial PCE. In contrast, devices with a SiO-barrier retained over 97% of initial PCE. To understand why 2D-PEAI passivated devices degrade faster than less efficient non-passivated devices, various opto-electrical and structural characterications are conducted. Together, these allowed to decouple different damage mechanisms. Notably, pseudo-J-V curves reveal unchanged high implied fill factors (pFF) of 86.4% and 86.2% in non-passivated and passivated devices, suggesting that degradation of the perovskite absorber itself is not dominating. Instead, inefficient charge extraction and mobile ions, due to a swiftly degrading PEAI interlayer are the primary causes of AtOx-induced device performance degradation in passivated devices, whereas a large ionic FF loss limits non-passivated devices.

Boosting the efficiency of organic solar cells based on a highly planar π-conjugated solid additive working as the sensitizer

Solid additives have been demonstrated as a simple and effective approach to improve the performance of organic solar cells (OSCs). The exploitation of excellent solid additive is an important aspect to obtain efficient OSC. This research designs and synthesizes a novel solid additive IDT(BDT-IC)2 as the sensitizer for OSCs. The IDT(BDT-IC)2 is an A-π-d-π-A type molecule, which possesses a highly planar π-conjugated structure. This molecule exhibits a complementary light absorption with suitable energy levels, which meets the requirement of a qualified sensitizer. It helps to enhance the external quantum efficiency spectrum of the device. Thus, an increased photocurrent is achieved. The addition of IDT(BDT-IC)2 promotes the formation of a cascade energy level alignment and tunes the miscibility of the active layer. Both the exciton dissociation and electron transportation are improved, which enhances the fill factor. As a result, the average power conversion efficiency (PCE) of the PM6:Y6 OSC is increased from 15.75 % of the control device to 16.34 % by incorporating merely 0.25 wt% of IDT(BDT-IC)2. And the highest PCE with a value of 16.70 % is obtained. This research offers a facile and effective strategy for highly efficient OSCs by applying solid additive as the sensitizer.

Artificial neural network-based optimization studies for efficient energy harvesting from auxetic laminated composite smart beam

In the present study, a smart laminated composite beam with auxetic configurations is considered to improve its energy harvesting capabilities. For this purpose, three different cases of auxetic geometries are considered on the cantilever laminated composite beam near the fixed end, and the piezoelectric patches are attached in bimorph configuration over this auxetic region. The coupled structural and piezoelectric equations are developed based on beam element theory. The principle of minimum potential energy is implemented to solve the equations of motion. Effective Young’s modulus and Poisson’s ratio of the auxetic geometric region are utilized in the beam model, and the results are validated with three-dimensional finite element solution. An experimental study is carried out to validate the finite element studies. The energy harvesting capability of laminated composite beam has significantly improved by using reentrant auxetic geometry. In addition to auxetic geometry, auxetic cubical inclusions are also considered to study their effect on energy harvesting potential. On validating the results obtained from auxetic geometry and auxetic cubical inclusion cases, some parametric studies are conducted to know the influence of auxetic inclusion dimensions, ply orientations, and thickness ratio on the voltage energy output. It is found that with an increase in the length and thickness of the auxetic geometry, the cross-ply oriented auxetic energy harvester’s output potential raised considerably. To obtain the optimum parameters required to enhance average output power and minimize the energy loss factor, grey-relational analysis tool, and artificial neural network-based optimization schemes are implemented. The energy harvesting system with the optimized parameters has shown about 60% improvement in the average power output and conversion efficiency.

Improved performance of kesterite Cu2ZnSn(S,Se)4 thin film solar cells by Ag/Ge co-doping

Cation doping is an important approach to improve the performance of kesterite Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cells. Since different cation dopant has different effects on the defects and crystallization of CZTSSe absorber, it is expected to achieve better device performance via the synergistic effects of double cation co-doping compared with the single cation doping. Herein, we investigated the effects of Ag/Ge co-doping on CZTSSe solar cells by doping Ge in an already optimized Ag-alloyed CZTSSe (ACZTSSe). It is found that incorporating a small amount of Ge can further improve the crystallinity and minority carrier lifetime of ACZTSSe. The low-temperature photoluminescence results reveal that the Ge doping primarily suppressed the SnZn defects in ACZTSSe, thereby further boosting the device performance. However, higher Ge doping concentration can lead to a discontinuous surface morphology, which is believed to be related with the relatively low melting temperature and double-layered structure of ACZTSSe absorber. The deteriorated surface morphology results in photocurrent loss in the near-infrared region and decreased fill factor. As the Ge doping ratio increases, there is a balance between the defects and morphology. A champion power conversion efficiency (PCE), 11.4%, was achieved for the Ag/Ge co-doped CZTSSe solar cells at Ge substitution rate of 3%. Compared with the single Ag doping, the average PCE was further promoted by 0.5% due to Ag/Ge co-doping.

An organic cathode for low-temperature processed, flexible ternary organic solar cells with high-performance.

In this study, we developed a flexible cathode for fabricating high-performance ternary organic solar cells (OSCs). With solvent engineering and acid treatment, the conductivity of the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) electrode was significantly enhanced with the sheet resistance reduced from 1081 to 83 Ω sq-1. After being coated with polyethylenimine, work function of the PEDOT:PSS electrode was tuned from -5.07 to -4.12 eV, which is beneficial for electron collection in OSCs. With this technique, the OSCs (on glass) showed an average power conversion efficiency (PCE) of 16.3%, which is comparable to that of conventional inverted OSCs with commonly used indium-tin oxide and sol-gel-processed zinc oxide. However, the processing temperature of the inverted OSCs was dramatically lowered from 200 to 120 °C. The flexible OSCs (on polyethylene naphthalate/PEDOT:PSS/PEIE) exhibited a high PCE of 14.1%. After being bended for 300 cycles, the PCE was only degraded by 8.5%, indicating the excellent bendability of the flexible OSCs with the organic cathode.