Increase In Open-circuit Voltage Research Articles

Double-layered printable electrolytes for highly efficient dye-sensitized solar cells

In this study, novel double-layered electrolyte architecture is first demonstrated for quasi-solid-state dye-sensitized solar cells (DSSCs). The experimental results show that the electrolyte prepared using 9 wt% polymer blends has rheological characteristics suitable for the printing process, and the corresponding DSSC with a double-layered electrolyte architecture reveals an efficiency (7.99%) comparable to that of a common liquid-state cell under 1 sun irradiation. Moreover, when zinc oxide (ZnO) nanoparticles are introduced as the additives in electrolytes, the open-circuit voltage (Voc) increases, whereas the short-circuit current density (Jsc) decreases. This phenomenon is attributed to the ZnO effects on the two electrodes, i.e., upward shift of the TiO2 conduction band at the photoelectrode and suppression of interfacial charge transfer at the counter electrode. A solution which takes advantage of the double-layered architecture is proposed herein to overcome the above dilemma. Electrolytes with and without the ZnO additives are printed onto the photoelectrode and counter electrode, respectively. The DSSC prepared by this solution maintains the high Voc, and furthermore, the Jsc increases, thus achieving an improved efficiency of 8.50%. A similar quasi-solid-state DSSC also outperforms its liquid-state counterpart under indoor fluorescent-light conditions, demonstrating impressive efficiencies beyond 15%.

Semi-transparent p-type barium copper sulfide as a back contact interface layer for cadmium telluride solar cells

Optically transparent p-type materials play a critical role in transparent electronics including photovoltaic (PV) devices. P-type sulfide materials offer an alternative to oxides for PV application due to improved hole transport properties. Here, we report the solution-based synthesis of earth-abundant p-type transparent conducting barium copper sulfide (α-BaCu4S3, BCS) thin films. These films were characterized using scanning electron microscopy, X-ray diffraction, UV–Vis–NIR spectrophotometry, Raman spectroscopy, and spectroscopic ellipsometry. BCS films of ~100 nm thickness transmit >70% of visible light. We report on tests of the hole transport properties of these BCS films for cadmium telluride (CdTe) photovoltaics, finding that the BCS deposition process forms a beneficial tellurium (Te) rich surface on CdTe by selectively removing Cd from the surface. Based on our study, the BCS interface layer plays dual functions for CdTe PV devices as a hole transport material and as an etchant, enhancing the resulting device performance. We observed a significant increase in open-circuit voltage of CdTe solar cells with the BCS buffer layer. Additionally, we discuss semitransparent CdTe solar cells with BCS as a hole transport layer and indium tin oxide as a finishing electrode. Semitransparent CdTe solar cells shows 13.3% conversion efficiency for the front side illumination and 1.2% efficiency for back side illumination, indicating high recombination of charge carriers generated close to the rear CdTe/BCS/ITO contact.

Pure sulfide Cu2ZnSnS4 layers through a one-step low-temperature PLD technique: Insight into simulation on modified back contact to overcome the barrier of MoS2

Targeting on the selenium free, pure sulfide kesterite compound (CZTS) allows retention of the higher band gap nontoxic absorber for a single-junction solar cell. In this work, CZTS thin films were deposited by the PLD method and the Structural/optical properties, as well as Mott–Schottky analysis, were studied at different substrate temperatures. Without undergoing the sulfurization process, the single-phase CZTS thin film is prepared at 300 ℃. In the second step, a numerical simulation is performed using the solar cell capacitance simulator to study the effect of the grading layer of MoS(Se)2 on the rear side of pure sulfide kesterite based solar cells. The device with a MoSe2 coated substrate exhibits better performance in comparison with the soda-lime-glass (SLG)/Mo that is susceptible to the formation of an n-type MoS2 intermediate layer. An improvement in conversion efficiency from 5.4% to 13.99%, often due to an increase of open-circuit voltage has been reached.

Increasing the Fluorine Substituent of Thieno[3,4-c]pyrrole-4,6-dione Terthiophene Copolymers Progressively Narrows the Nanofibrils and Enhances the Efficiency of Fullerene-Based Polymer Photovoltaics

Five thieno­[3,4-c]­pyrrole-4,6-dione (TPD)-terthiophene copolymers, PHT, P1F3HT, P1F1HT, P3F1HT, and PFT, having 0, 25, 50, 75, and 100% of fluorine substituents on the center of terthiophene exhibit a progressive increase of open-circuit voltage (VOC), short-circuit current density (JSC), and hence a power conversion efficiency (PCE) up to 9.68% of PC61BM-blended copolymer photovoltaics, which is the highest PCE reported for TPD-based polymer solar cells with fullerene derivatives as the electron acceptor. It is evident in atomic force microscopy and transmission electron microscopy studies that the width of copolymer nanofibrils formed in solar cells decreases progressively with the increasing fluorine substituents of the copolymers. A declining solubility, which is attributed to the fluorophobic effect, narrows the nanofibril of copolymers with more fluorine substituents. Grazing incidence wide angle X-ray scattering studies reveal the improved crystallinity of lamellar stacking and π–π stacking structures of copolymers with more fluorine substituents. Density functional theory calculation indicates a virtually coplanar conformation of terthiophene units with fluorine substituents. The increasing VOC is also associated with the increasing fluorine substituents, which lower the highest occupied molecular orbital energy level of the copolymers verified by the electrochemical and photoelectron spectroscopic measurements.

Enhanced performance of diamond Schottky nuclear batteries by using ZnO as electron transport layer

Improving open-circuit voltage is critical to improving the performance of diamond nuclear battery. ZnO films have been successfully used as the electron transport layer of diamond Schottky nuclear battery in this work. The open-circuit voltage of device with ZnO layer is increased from 1.03 to 1.43 V and the conversion efficiency is increased by 100% to 1.42% compared with device without ZnO layer. By comparing the device structure diagram and potential distribution before and after adding the ZnO layer, we try to find out the cause of the increase in open-circuit voltage. This research provides a new way to improve the open-circuit voltage and conversion efficiency of nuclear batteries.

Modulation of Field-Effect Passivation at the Back Electrode Interface Enabling Efficient Kesterite-Type Cu2ZnSn(S,Se)4 Thin-Film Solar Cells.

For further efficiency improvement in kesterite-type Cu2ZnSn(S,Se)4 (CZTSSe) solar cells, it is essential to address the carrier recombination issue at the back electrode interface (BEI) caused by the undesirable built-in potential orientation toward an absorber as an n-MoSe2 interfacial layer formed. In this regard, back surface field (BSF) incorporation, i.e., field-effect passivation, shows promise for dealing with this issue due to its positive effect in decreasing recombination at the BEI. In this study, the BSF was realized with the p-type conduction transition in interfacial layer MoSe2 by incorporating Nb into the back electrode. The BSF width can be tuned via modulating the carrier concentration of the absorber, which has been demonstrated by capacitance-voltage characterization. A beyond 7% efficiency BSF-applied CZTSSe solar cell is prepared, and the effects of a tunable BSF and the mechanism underpinning device performance improvement have been investigated in detail. The wider BSF distribution in the absorber induces a decrease in reverse saturation current density (J0) due to the stronger BSF effect in suppressing BEI recombination. As a result, an accompanying increase in open-circuit voltage (VOC) and short-circuit current density (JSC) is achieved as compared to the BSF-free case. This study offers an alternative strategy to address the BEI recombination issue and also broadens the interface passivation research scope of potentially competitive kesterite solar cells.

Defect properties of solar cells with layers of GaP based dilute nitrides grown by molecular beam epitaxy

Dilute nitrides lattice-matched to GaP were studied to explore the possibilities to improve their properties by additional indium or arsenic content in the GaPN alloy for further utilization in solar cells. Admittance spectroscopy shows that intrinsic layers of GaPNAs and InP/GaPN grown by molecular-beam epitaxy have unintentional background silicon donor doping. Deep-level transient spectroscopy allowed us to reveal several defect levels. In GaPNAs, two defect levels were detected at Ec − 0.58 eV and Ev + 0.44 eV, with respective concentrations of 4 × 1015 cm−3 and 2 × 1015 cm−3. After thermal annealing, these could be reduced by a factor of two and by more than one order of magnitude, respectively, leading to an increase of external quantum efficiency and open-circuit voltage of solar cells. The InP/GaPN layer exhibits a defect level at Ec − 0.44 eV (with a concentration of 2 × 1014 cm−3), which is of similar nature as the one at Ec − 0.58 eV in GaPNAs. Furthermore, unlike in GaPNAs, defect levels close to midgap were also detected in the InP/GaPN layer. These non-radiative recombination centers lead to poorer photoelectric properties of solar cells based on InP/GaPN as compared to those based on GaPNAs. Therefore, the introduction of arsenic in the compound and post-growth thermal annealing allowed us to reduce the defect concentrations in dilute nitrides and improve photoelectrical properties for photovoltaic applications.

Temperature dependent device characteristics of graphene/h-BN/Si heterojunction

Graphene-on-semiconductor heterojunction solar cell is an emerging class of photovoltaics (PV) with potential for efficient and reliable energy conversion systems. The interface between graphene and a lightly doped semiconductor plays a key role in charge-carrier separation and recombination dynamics. Owing to the low Schottky barrier height (ϕSBH)-induced interfacial charge carrier recombination, graphene-on-silicon (Si) heterojunction solar cells suffer from instability in power conversion efficiency over time. Therefore, it is critical to engineer the interface to enhance the barrier height by interfacing a chemically stable, insulating, and atomically thin layer. Further, the temperature dependent photovoltaic characteristics of such stacked architectures are unknown, and temperature dependent behavior is critical to understand the metal-insulator-semiconductor (MIS) junction behavior and photovoltaic phenomenon. Here, we have introduced hexagonal boron nitride (h-BN) as a tunneling interlayer in graphene-on-Si heterojunction solar cells, which enables the passivation of the chemical dangling bonds on the Si surface. The effect of temperature on the performance of a graphene/h-BN/Si PV cell is examined. Thin films of h-BN are directly synthesized on a lightly doped Si surface via a bottom-up chemical-surface-adsorption strategy followed by the transfer of a graphene monolayer. The 2D layer-on-2D layer-on-3D bulk semiconductor nanoarchitecture of graphene/h-BN/Si forms a MIS-type junction, where the h-BN acts as an electron-blocking layer to avoid interfacial charge carrier recombination. A four-fold increase in open-circuit voltage (Voc) is found for the graphene/h-BN/Si heterojunction cell (0.52 V) in contrast to the graphene/Si cell (0.13 V), which is due to the increase in the ϕSBH and hence built-in electric potential. Interestingly, the Voc linearly decreases by only ~4% with every 10 K increase in temperature. This work will lead to the evolution of new 2D/2D/3D nanoarchitectures for mechanically robust, high performance, and durable optoelectronic functionalities.

Highly efficient, stable and hysteresis‒less planar perovskite solar cell based on chemical bath treated Zn2SnO4 electron transport layer

Abstract The electron transport layer (ETL) is a key constituent in perovskite solar cells (PSCs). It should provide efficient and selective electron extraction, low resistivity and high stability. Here, zinc stannate (Zn2SnO4, ZSO) is employed as an ETL in planar PSCs. A surface treatment of a compact ZSO layer is introduced based on chemical bath deposition (CBD). CBD results in a dense and uniform surface morphology that promotes the formation of a perovskite film with better surface coverage and enlarged grains, which lead to reduced recombination losses. Such improvements effectively increase the charge extraction at ETL/perovskite interface and reduce trap‒assisted recombination, which results in a remarkable photovoltaic performance, low hysteresis index, and good reproducibility. The efficiency of PSCs based on CBD‒modified ZSO ETL has been dramatically increased from 19.3% to 21.3% with a notable increase in open circuit voltage of 60 mV compared to bare ZSO‒based devices. This value is among the highest for ZSO‒based PSCs. More importantly, the CBD‒treated PSCs exhibited good stability, retaining more than 90% of its initial efficiency over 1000 h under continuous illumination at maximum power point. These results demonstrate that CBD can significantly improve the performance and stability of ZSO‒based planar PSCs, a crucial requirement for commercialization.

50% transparent solar cells of CuO /TiO2: Device aspects

Abstract In this study, we have fabricated type-I straddling gap heterojunction solar cells of Ag/CuOx/TiO2/FTO configuration utilizing extremely thin p-n junction of 150 nm. We have studied four unique devices by varying the oxygen vacancies in CuOx and its effect on the overall performance of the cells. The average transmittance of 28–52% made these devices semitransparent for visual perception and transparent for visible spectrum of the Sun. The solar cell characteristics were recorded for 365 nm UV light which showed a linear increase in open circuit voltage (Voc) from 0.266 to 1.01 V while changing CuOx phases from Cu2O to CuO. However, a non-linear trend was observed for the photocurrent density and that has been discussed in detail by considering both material and device aspects. The optimized solar cell with CuO active layer possessed Voc of 1.01 V with 3.48 mA/cm2 current density and fill factor (FF) of 31% which sums up to an overall efficiency of 16.22% for an input power of 7 mW/cm2. The electrical parameters of solar cells were analyzed by using a two-diode model and the influence of TiO2 buffer layer has been discussed by the charge transfer mechanisms using the band diagrams. It was found that CuO/TiO2 device offered highest efficiency due to large Δ E c which increased the tunneling probability of minority charge carriers and reduced the recombination process at the interface. This study is the first experimental report on CuOx/TiO2 heterojunction solar cell which may find applications to design fancy and semitransparent power generating windows with colors yellow to brown by varying CuOx stoichiometry.

FAPbI3‐Based Perovskite Solar Cells Employing Hexyl‐Based Ionic Liquid with an Efficiency Over 20% and Excellent Long‐Term Stability

AbstractFormamidinium lead triiodide (FAPbI3)‐based perovskite materials are of interest for photovoltaics in view of their close‐to‐ideal bandgap, allowing absorption of photons over a broad solar spectrum. However, FAPbI3‐based materials suffer from a notorious phase transition from the photoactive black phase (α‐FAPbI3) to nonperovskite yellow phase (δ‐FAPbI3) under ambient conditions. This transition dramatically reduces light absorbtion, thus, degrading the photovoltaic performance and stability of ensuring solar cells. In this study, 1‐hexyl‐3‐methylimidazolium iodide (HMII) ionic liquid (IL) is employed as an additive for the first time in FAPbI3 perovskite to overcome the above‐mentioned issues. HMII incorporation facilitates the grain coarsening of FAPbI3 crystal owing to its high‐polarity and high‐boiling point, which yields liquid domains between neighboring grains to reduce the activation energy of the grain‐boundary migration. As a result, the FAPbI3 active layer exhibits micron‐sized grains with substantially suppressed parasitic traps with an Urbach energy reduced by 2 meV. Hence, the resulting perovskite solar cell achieves an efficiency of 20.6% with notable increase in open circuit voltage (VOC) of 80 mV compared with HMII‐free cells (17.1%). More importantly, the HMII‐doped FAPbI3‐based cells show a striking enhancement in shelf‐stability under high humidity and thermal stress, retaining >80% of their initial efficiencies at 60 ± 10% relative humidity and ≈95% at 65 °C.

Biopolymer passivation for high-performance perovskite solar cells by blade coating

Abstract Thin films of perovskite deposited from solution inevitably introduce large number of defects, which serve as recombination centers and are detrimental for solar cell performance. Although many small molecules and polymers have been delicately designed to migrate defects of perovskite films, exploiting credible passivation agents based on natural materials would offer an alternative approach. Here, an eco-friendly and cost-effective biomaterial, ploy- l -lysine (PLL), is identified to effectively passivate the defects of perovskite films prepared by blade-coating. It is found that incorporation of a small amount (2.5 mg mL−1) of PLL significantly boosts the performance of printed devices, yielding a high efficiency of 19.45% with an increase in open-circuit voltage by up to 100 mV. Density functional theory calculations combined with X-ray photoelectron spectroscopy reveal that the functional groups ( NH2, COOH) of PLL effectively migrate the Pb-I antisite defects via Pb-N coordination and suppress the formation of metallic Pb in the blade-coated perovskite film. This work suggests a viable avenue to exploit passivation agents from natural materials for preparation of high-quality perovskite layers for optoelectronic applications.

Enhanced photovoltaic performance and stability of perovskite solar cells by interface engineering with poly(4-vinylpyridine) and Cu2ZnSnS4&CNT

Organic-inorganic perovskite solar cells (PSCs) are emerging candidates for next generation photovoltaic devices. In the last decade, PSCs have depicted a rapid development in device performance, meanwhile, the issue of utilizing low-cost, non-toxic materials with chemical stability as well as long term device stabilities are still lacking. To address these issues, an inexpensive, eco-friendly, and environmentally stable nanostructure of the quaternary chalcogenide Cu2ZnSnS4 (CZTS) as an inorganic hole transport material (HTM) has been investigated. Moreover, simultaneously two strategies has been employed to optimize the photovoltaic parameters. First, an interlayer of poly(4-vinylpyridine) (PVP) has been applied between the perovskite and the hole transport layer (HTL). Second, single-walled carbon nanotubes (CNTs) is incorporated into the CZTS HTL. While, the latter only result in higher short circuit current density (Jsc) from 18.3 to 20 mA cm−2, by using both of the strategies an increase in open circuit voltage (Voc) from 0.98 to 1.05 V as well as Jsc from 18.3 to 20.5 mA cm−2 has been observed. The power conversion efficiency (PCE) of the record device reached to 15.2%, fill factor (FF) increased up to 70% and also demonstrated low hysteresis of 2.3%. The formation of hydrophobic CNT webs among the sphere-like CZTS nanostructures and the presence of the PVP polymeric interlayer results in highly stable devices, which retained more than 98% of the initial PCE at room temperature and 40–45% humidity after 30 days. Thus, our results show that the combination of PVP interlayer and CZTS&CNT HTL offer an opportunity for the scalability of PSCs.

Effect of humidity on tribological properties and electrification performance of sliding-mode triboelectric nanogenerator

For vertical contact-separation-mode triboelectric nanogenerator (TENG), the hydrophobic surface is often used to improve the electrical output under high humidity condition. However, for sliding-mode TENG, the triboelectric effect is accompanied with the friction and wear of material, and whether the hydrophobic surface is beneficial to the durability as well as the stability of electrical output has been really ambiguous. In the paper, the pillar arrays with different pitches are fabricated through lithography, deep reactive ion etching and replication techniques to get the hydrophobic surface with different static contact angle. Based on the test platform with humidity control system, the effects of pillar pitch and normal force on the coefficient of friction, mass loss, and open-circuit voltage are investigated experimentally at different relative humidity condition. The results show that the effect of humidity on electrical output for sliding-mode TENG is different from that for vertical contact-separation-mode TENG. For a certain patterned surface of sliding-mode TENG, the coefficient of friction, short-circuit current and open-circuit voltage increase with the increasing relative humidity at first and diminish afterwards. The maximum values of them are achieved at 50% relative humidity. The mass loss diminishes with the increment of relative humidity. For surfaces with different pillar pitch, the coefficient of friction and open-circuit voltage decrease with the increasing pillar pitch, while the mass loss increases. Moreover, the decrease in pillar pitch, in which the contact angle of surface is increased, can improve the durability as well as the stability of output of sliding-mode TENG. In addition, although the greater normal force can enhance the stability of open-circuit voltage for sliding-mode TENG under humidity condition, the contact angle of surface will be reduced more obviously in the process of wear, speeding up the failure of hydrophobic surface. This study reveals the effect of hydrophobic surface on the durability as well as the stability of output for sliding-mode TENG and provides reference for texture design at different humidity conditions.

Performance enhancement of small molecular solar cells via luminescent sensitizer 4,5-bis(carbazol-9-yl)-1,2-dicyanobenzene (2CzPN)

Enhanced performance of small molecule organic solar cells is presented by incorporating a blue luminescent sensitizer layer 4,5-bis(carbazol-9-yl) -1,2-dicyanobenzene (2CzPN). As a result, 68% enhancement of power conversion efficiency is achieved from 1.54% (without sensitizer 2CzPN) to 2.60% (with 3 nm 2CzPN). The improvement is attributed to the increase of photocurrent and open-circuit voltage (VOC) because of subphthalocyanine (SubPc) reabsorption of photon from the emission of 2CzPN. The absorption spectrum of 2CzPN is complementary with the donor SubPc, and its photoluminescence spectrum overlaps with the absorption spectrum of the active layer. The VOC increases from 0.98 V to 1.17 V due to the slightly deeper highest occupied molecular orbital level of 2CzPN than SubPc. The estimated hole injection barrier slightly increases from 0.809 eV (without 2CzPN) to 0.874 eV (with 5 nm 2CzPN) and the hole mobility simultaneously decreases. This strategy provides a facile approach for effective utilization of high-energy photons.

Modelling and analysis of functionally graded carbon nano-tube reinforced composite material based energy harvester

In recent years, harvesting the waste energy is one of the major concerns for mankind. With the improvement in micro and nano-electro mechanical system, the energy consumption of various components is reducing resulting in the application of wireless devices at larger scale. In the present study, a piezoelectric material-based energy harvester is modelled and analysis is carried out in context of open circuit voltage. The energy harvester is numerically modelled using finite element technique by incorporating the coupled electro-mechanical physics and the properties of carbon nano-tube reinforced composite structure. The influence of distribution of the carbon nano-tubes and also the volume fraction of the carbon nano-tubes on the open circuit voltage is investigated. FG-X distribution of volume fraction demonstrates approximately 5.6% and 7.2% increase in open circuit voltage compared to UD volume fraction for 11% and 17% respectively.

Experimental investigation on electrode wear of array holes machining in micro-EDM

Electrode wear is crucial for the machining accuracy of array holes in micro-EDM. In order to improve the accuracy and efficiency of array holes machining, the compensation for electrode wear is required. In this study, the effects of essential factors including power modes, open-circuit voltage, capacitance, current limiting resistance, workpiece thickness and electrode diameter on electrode wear were investigated through single factor experiments. It was found that using a TR power supply, lower open circuit voltage could minimize the electrode wear. Electrode wear increases with the increase of open-circuit voltage, workpiece thickness and the number of processed holes, for RC and TC power modes, it decreases firstly and then increases as the capacitance increases. In TC power mode, electrode wear increases with the decrease of current limiting resistance. Moreover, the influencing mechanism of factors on electrode wear were also discussed. In this paper, the functional relations between electrode wear, workpiece thickness and electrode diameter were established, and a compensation strategy for microarray holes machining was proposed to fabricate 5×6 microarray holes, of which the aperture deviation is less than 2 μm and the average diameter is 115 μm. The results of this work are expected to be helpful to provide a basis for the strategy of electrode wear compensation in micro array holes fabrication.

In-situ stress modulated ferroelectric photovoltaic effect in cluster-assembled TbFe2/Bi5Ti3FeO15 heterostructural films

TbFe2/Bi5Ti3FeO15 heterostructural films were prepared by inserting cluster-assembled TbFe2 microdiscs into a Bi5Ti3FeO15 matrix using low energy cluster beam deposition combined with sol-gel methods. The phase structure, ferroelectric properties, bandgap, photovoltaic spectral response, and performances of the ferroelectric photovoltaic effect were modulated by the in situ stress driven by magnetostriction of TbFe2 clusters under external magnetic fields. The short-circuit current, open-circuit voltage, and power conversation efficient increase with the in situ stress, reaching 0.026 mA/cm2, 9.5 V, and 5.88 × 10−2%, respectively, under a maximum in-stress of 0.075 GPa. So the high open-circuit voltage above bandgap is attributed to the distinct bandgap shifting and the effective separation of photogenerated electron-hole pairs derived from the in situ stress induced large built-in field. The in situ stress dominated symmetry breaking contributes to the improvement of the power conversation coefficient. The in situ dynamic internal stress provides a high efficient approach to modulate and improve ferroelectric photovoltaic effects.

Electrostatic adsorption of a fluorophores-modified light-harvesting complex II on TiO2 photoanodes enhances photovoltaic performance

The major light-harvesting complex of photosystem II, or LHCII, has been utilized in photovoltaic applications because of its high pigment density. In vitro assembled recombinant LHCII is a modifiable biomimetic material for solar energy conversion. In this report, we assemble a modified recombinant LHCII from apoproteins covalently conjugated artificial fluorophores Atto 590 which absorb greatly near visible green region, where LHCII possesses relatively weak absorption. The absorption and fluorescence excitation spectra indicate that the modified recombinant LHCII possesses enhanced light harvesting capacity because Atto 590 molecules efficiently transfer energy to LHCII. The unmodified or modified recombinant LHCII is then adsorbed on the TiO2 electrode respectively to construct sensitized solar cells, both of which present remarkable photovoltaic enhancement. The incident photon-to-electron conversion efficiency measurements confirm the contribution of the artificial fluorophores. The modified recombinant LHCII sensitized solar cell presents 9.1% increase in open circuit voltage and 13.6% increase in short-circuit current density, compared to the unmodified one. These results suggest that modifications of the recombinant LHCII are feasible ways to enhance its performance in biophotovoltaic cells.

Real-Time Electron Nanoscopy of Photovoltaic Absorber Formation from Kesterite Nanoparticles

Cu2ZnSnS4 nanocrystals are annealed in a Se-rich atmosphere inside a transmission electron microscope. During the heating phase, a complete S-Se exchange reaction occurs while the cation sublattice and morphology of the nanocrystals are preserved. At the annealing temperature, growth of large Cu2ZnSnSe4 grains with increased cation ordering is observed in real-time. This yields an annealing protocol which is transferred to an industrially-similar solar cell fabrication process resulting in a 33% increase in the device open circuit voltage. The approach can be applied to improve the performance of any photovoltaic technology that requires annealing because of the criticality of the process step.