Photovoltaic Response Research Articles

Photovoltaic response promoted via intramolecular charge transfer in triphenylpyridine core with small acceptors: A DFT/TD-DFT study

Currently, A−π−A configured molecules (TTP1-TTP6) were designed from the reference compound (TPPR) by modifying the terminal acceptors for photovoltaic materials. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) using the M06/6-311G(d,p) functional were employed to analyze the photonic and electronic properties of the newly designed derivatives. Various analyses; frontier molecular orbitals (FMOs), density of states (DOS), absorption spectra (λmax), transition density matrix (TDM), binding energy (Eb), hole-electron and open circuit voltage (Voc) were performed to explore the photovoltaic properties of triphenylpyridine based compounds. The structural modulation with acceptor moieties significantly tuned their HOMO and LUMO levels, resulting in reduced band gaps (2.833–3.037 eV). They also exhibited broader absorption spectra (λmax) ranging from 482.560 to 514.756 nm as compared to the reference compound (486.289 nm). Notably, TPP3 showed the good photovoltaic response as it displayed the least energy gap (2.833 eV) with lower binding energy (0.415 eV) and bathochromic shift (512.798 nm) in absorption spectra as compared to all other derivatives. Beside this, a comparative study with spiro-OMeTAD and P3HT standard hole transport materials illustrated that these materials can also be utilized as effective photovoltaic materials.

Controlled growth of two-dimensional MoS2/WSe2 heterostructure solar cell by chemical vapor deposition

The development of high-quality type II semiconductor heterostructures is crucial for solar energy conversion applications. Here, we report the sequential growth of MoS2/WSe2 two-dimensional semiconductor type II heterostructure using a one-step chemical vapor deposition. The morphological, Raman, and chemical analysis revealed that the WSe2 layer is deposited on the rhombus-shaped MoS2, forming a vertical MoS2/WSe2 heterostructure. The solar cell fabricated using the grown heterostructure exhibits a photovoltaic response with a conversion efficiency of 2.5 % and an open circuit voltage of 0.22 V, respectively. The numerical simulation study unravels the mechanism of charge separation and transport in the MoS2/WSe2 heterostructure solar cell.

Self-driven Te0.65Se0.35/GaAs SWIR photodiode with spectral response to 1.55 μm for broadband imaging and optical communication

Te-based photodetectors with the merits of low cost and CMOS-compatible fabrication process have been considered promising for broadband imaging applications. Nevertheless, the spectral response of reported devices under self-powered mode is generally limited to near-infrared wavelength below 1100 nm (corresponding to the bandgap of Si). This could be ascribed to the high room-temperature carrier density in Te and the ease of forming Type-I heterojunctions between Te and other semiconductors, which impede the effective generation and separation of photocarriers. This study reports the bandgap engineering of Te through Te-Se alloying and the fabrication of Te0.65Se0.35/Al2O3/GaAs photodiode with an extended response spectrum through ultraviolet to the short-wave infrared (SWIR) band of 1550 nm at zero bias. The effects of interface passivation on the photosensing properties were also investigated. The optimized heterojunction exhibits a pronounced photovoltaic response to 1342 nm (1550 nm) infrared light with an open-circuit voltage of ∼0.12 V (0.07 V). Particularly, the dark current density reaches a record low level of 0.1 nA/cm2 at 0 V bias, leading to a high on-off current ratio of 4.5×104 and detectivity of 1.1×107 Jones at room temperature for 1342 nm light. Self-powered UV-Vis-SWIR broadband imaging and optical communication are realized by leveraging the favorable device performance. Our work provides a frame of reference for exploring more Te1-xSex-based photodetectors. Meanwhile, it may be combined with well-developed semiconductor processing technologies for optoelectronics integration.

Investigation of the effects of thermal annealing to PEDOT:PSS on the photovoltaic response of hybrid solar cells

Investigation of the effects of thermal annealing to PEDOT:PSS on the photovoltaic response of hybrid solar cells

Structural Modeling of Fluorinated Quinoxaline Core–Based Chromophores for Efficient Photovoltaic Materials: A DFT Study

ABSTRACTHerein, a series of fluorinated quinoxaline core–based chromophores (MTH1‐MTH6) with A1–π–A2–π–A1 configuration was designed by structural modulation of end‐capped acceptors in MTHR. The quantum chemical calculations were accomplished at MPW1PW91/6‐311G(d,p) functional to explore optoelectronic and photovoltaic properties of these designed compounds. The findings revealed that all the derivatives exhibited narrow band gap (Egap = 2.163–2.666 eV) with red shift spectra (610.24–766.944 eV in chloroform) as compared with MTHR. The designed compounds exhibited comparable open‐circuit voltage (Voc) and higher power conversion efficiencies (PCEs) as compared with the MTHR. Among the entitled chromophores, MTH1 was found to be a promising chromophore for organic solar cells (OSCs) owning to its lowest Egap (2.163 eV) with highest absorption peak (766.944 nm in chloroform and 717.709 nm in gaseous phase). The aforementioned findings indicate that molecular engineering of chromophores with extended acceptors enhances photovoltaic response, and this motivates researchers to develop highly effective photovoltaic devices.

Heart Engineering of Photovoltaic Devices: Preparation of New Ru Dyes Using Thioindigo and Phenothiazine

ABSTRACTPhenothiazine and thioindigo were used as substitutes to make new Ru dyes for DSSCs. The thioindigo unit is a notable molecule with strong technical qualities in these photosensitizers. As a result, research was done on the cyano substituent as an electron‐donating group. Both theoretical and experimental methods were used to assess the complexes' optical response. A better photovoltaic response is achieved by the cyano groups' efficient bonding with the semiconductor layer. Additionally, the complexes that were formed contain two different kinds of electron accepter substituents: cyanoacrylic acid and carboxylic acid, with efficiencies of 7.42% and 4.17%, respectively. Additionally, cosensitization was investigated and analyzed utilizing N719 and two generated complexes. DSSCs made with Complex 1 and 2 and N719 have corresponding efficiency percentages of 8.86% and 9.74%.

A Photovoltaic Self-Powered Volatile Organic Compounds Sensor Based on Asymmetric Geometry 2D MoS2 Diodes

Transition metal dichalcogenides have gained considerable interest for vapour sensing applications due to their large surface-to-volume ratio and high sensitivity. Herein, we demonstrate a new self-powered volatile organic compounds (VOC) sensor based on asymmetric geometry multi-layer molybdenum disulfide (MoS2) diode. The asymmetric contact geometry of the MoS2 diode induces an internal built-in electric field resulting in self-powering via a photovoltaic response. While illuminated by UV-light, the sensor exhibited a high responsivity of ∼60% with a relatively fast response time of ∼10 sec to 200 ppm of acetone, without an external bias voltage. The MoS2 VOC diode sensor is a promising candidate for self-powered, fast, portable, and highly sensitive VOC sensor applications.

A Comprehensive DFT Exploration of Physical Characteristics of Halide Double Perovskites Na2AgGa(Cl/Br)6: Environment-Friendly Alternatives for Renewable Energy Technologies

This work elucidates the comprehensive exploration of the stability, electronic aspects, and photovoltaic response and ability to utilize thermal energy of Na2AgGa(Cl/Br)6. The cubic phase and thermal stability are evaluated based on the depicted tolerance factor and formation enthalpy. The depicted electronic attributes comprehensively clarified the p-type nature of materials. The value of the obtained direct energy gap is reduced from 1.85 eV to 1.13 eV by replacing Na2AgGaCl6 with Na2AgGaBr6. The scrutiny of distributed states across bands is also explained by analyzing states’ partial and total density. Furthermore, the assessed optical properties indicate that these compounds exhibit considerable absorption values across the visible-ultraviolet spectrum. The optical characteristics suggest that these perovskites exhibit minimal loss of power and have an increased ability to capture light, making them well-suited for use in solar power generation. Using the BoltzTraP code, thermoelectric parameters have been scrutinized, uncovering a significant relationship between increased electrical conductivity and decreased heat transfer. The elastic properties are examined to ascertain the ductile characteristics, symmetry or asymmetry, and stability under applied stress. The combination of a higher absorption and ZT value indicates that these compounds have significant potential for generating power using light and dissipated heat.

Structural and excitonic properties of the polycrystalline FAPbI3 thin films, and their photovoltaic responses

Faormamadinium based perovskites have been proposed to replace the methylammonium lead tri-iodide (MAPbI3) perovskite as the light absorbing layer of photovoltaic cells owing to their photo-active and chemically stable properties. However, the crystal phase transition from the photo-activeα-FAPbI3to the non-perovksiteδ-FAPbI3still occurs in un-doped FAPbI3films owing to the existence of crack defects, which degrads the photovoltaic responses. To investigate the crack ratio (CR)-dependent structure and excitonic characteristics of the polycrystalline FAPbI3thin films deposited on the carboxylic acid functionalized ITO/glass substrates, various spectra and images were measured and analyzed, which can be utilized to make sense of the different devices responses of the resultant perovskite based photovoltaic cells. Our experimental results show that the there is a trade-off between the formations of surface defects and trapped iodide-mediated defects, thereby resulting in an optimal crack density or CR of the un-dopedα-FAPbI3active layer in the range from 4.86% to 9.27%. The decrease in the CR (tensile stress) results in the compressive lattice and thereby trapping the iodides near the PbI6octahedra in the bottom region of the FAPbI3perovskite films. When the CR of the FAPbI3film is 8.47%, the open-circuit voltage (short-circuit current density) of the resultant photovoltaic cells significantly increased from 0.773 V (16.62 mA cm-2) to 0.945 V (18.20 mA cm-2) after 3 d. Our findings help understanding the photovoltaic responses of the FAPbI3perovskite based photovoltaic cells on the different days.

Enhancement of Near‐Infrared Photovoltaic Response of Si/Au Schottky‐Junction Structure by Band‐Bending Approaches

A combined approach of band bending is employed to enhance the near‐infrared (NIR) photovoltaic (PV) response of a Si/Au Schottky junction (SHJ) device. As a reference, the basic architecture of the SHJ device consists of textured n‐Si and gold nanoparticles (Au NPs). Its photoelectric conversion efficiency at 1319 nm wavelength is 0.0302%. A series of band‐bending approaches are then applied to the reference device in sequence, aiming to minimize the electric loss of the structure by strengthening built‐in electric field. These approaches include introductions of an Al2O3 layer for front field passivation, a p+‐Si layer to form a p+n‐like junction at the front of the device and a SiO2 layer for rear field passivation. With these modifications, under 1319 nm illumination, the open‐circuit voltage eventually increases by 14%, the short‐circuit current increases by 18% and the photoelectric conversion efficiency of the device increases by 66% to reach 0.0501%. The results of this work propose a strategy to minimize the electric loss in an NIR PV device.

Pressure‐Regulated Photovoltaic Response in Antimony Triiodide With Asymmetric Metal Contact

AbstractThe effective modification of photovoltaic activities in photoelectric devices is significant for enhancing energy conversion efficiency. Here, the pressure‐tunable photovoltaic properties in the SbI3 device with Au/Pt asymmetric electrodes are demonstrated. At initial pressure, the SbI3 device exhibits an anticipated self‐driven photoresponse characteristic at zero external bias, and a significant enhancement in photocurrent response is observed with increasing bias to −0.2 V, nearly two orders of magnitude higher than the initial value. With increasing pressure, the SbI3 device exhibits tunable photocurrent response, reaching a maximum value at ≈1.2 GPa, while the photovoltage response decreases monotonously during compression, which is closely associated with the dynamic evolution of the work function and bandgap of SbI3 upon successive compression. These findings signify that SbI3 is a promising candidate for future photoelectric devices, which opens a new window of opportunity for further exploration, regulation, and understanding of high‐performance photovoltaic devices under extreme conditions.

Scaling Behavior in the Spectral and Power Density Dependent Photovoltaic Response of Hot Polaronic Heterojunctions

AbstractStrongly correlated manganites can be considered as model systems for the study of photovoltaic harvesting of hot polarons that can be excited from the electronically ordered ground state. In order to gain basic understanding of hot polaron harvesting, the deviations of the photovoltaic response of a heterojunction with polaronic absorber from a conventional semiconductor are analyzed. Specifically, the spectral and photon power density dependence of the open circuit voltage Uoc and the short circuit current density Jsc in heterojunctions consisting of orbital ordered Pr1‐xCaxMnO3 (x = 0.1, PCMO) thin films epitaxially grown on single crystalline (100) SrTiO3 (STO) and Nb‐doped (100) SrTiO3 (STNO) substrates are investigated. The observed behavior is fundamentally different from conventional solar cells, in which Uoc is limited by fast carrier relaxation to the band edges. Whereas the spectral and photon power dependence of Uoc of conventional semiconductor junctions is well described by the Shockley‐Queisser (SQ) theory, the hot polaron junctions surprisingly show a scaling law behavior of Uoc. Such scaling laws otherwise apply to equilibrium order parameters in second‐order phase transitions. It is concluded that its physical origin is the unique dependence of the quasi‐Fermi level splitting on temperature, photon energy, and power density in a hot polaron system.

DFT-Based Tailoring of the Thermoelectric and Photovoltaic Response of the Halide Double Perovskite Cs2TlYF6 (Y = Ag, Co)

DFT-Based Tailoring of the Thermoelectric and Photovoltaic Response of the Halide Double Perovskite Cs2TlYF6 (Y = Ag, Co)

Sliding Ferroelectricity Induced Ultrafast Switchable Photovoltaic Response in ε-InSe Layers.

2D sliding ferroelectric semiconductors have greatly expanded the ferroelectrics family with the flexibility of bandgap and material properties, which hold great promise for ultrathin device applications that combine ferroelectrics with optoelectronics. Besides the induced different resistance states for non-volatile memories, the switchable ferroelectric polarizations can also modulate the photogenerated carriers for potentially ultrafast optoelectronic devices. Here, it is demonstrated that the room temperature sliding ferroelectricity can be used for ultrafast switchable photovoltaic response in ε-InSe layers. By first-principles calculations and experimental characterizations, it is revealed that the ferroelectricity with out-of-plane (OOP) polarization only exists in even layer ε-InSe. The ferroelectricity is also demonstrated in ε-InSe-based vertical devices, which exhibit high on-off ratios (≈104) and non-volatile storage capabilities. Moreover, the OOP ferroelectricity enables an ultrafast (≈3ps) bulk photovoltaic response in the near-infrared band, rendering it a promising material for self-powered reconfigurable and ultrafast photodetector. This work reveals the essential role of ferroelectric polarization on the photogenerated carrier dynamics and paves the way for hybrid multifunctional ferroelectric and optoelectronic devices.

Characterization of polycrystalline bulk ferroelectric ZnSnS3 synthesized by hydrothermal method for photovoltaic application

ZnSnS3, a newly theoretically predicted ferroelectric material which shows promising properties for solar cell and photovoltaic applications, was successfully grown in our laboratory by hydrothermal method. The high intensity x-ray diffraction pattern from the (211), (101̅), (200), (210), (310), (320), and (321̅) planes reveal the crystalline character of the trigonal ZnSnS3 phase. The microstructural property and elemental distribution were evaluated using SEM and TEM studies. Diffuse reflectance measurement at room temperature shows a direct bandgap of 2.62 eV along with a high energy direct transition of 3.13 eV. Two broad photoluminescence peaks at various temperatures (4–300 K) were also detected around (2.61–2.73 eV) and (3.04–3.11 eV). The emission characteristics are explained considering the shallow donor level to valence band transitions. Raman study elucidates that the synthesized ZnSnS3 possess a good number of Raman active bands. A phase transition from the ferroelectric to non-ferroelectric phase of ZnSnS3 is observed around 330 °C in DSC and dielectric measurements. The P-E measurement showed that the material is ferroelectric in nature with saturation polarization value of 21.85μC/cm2. The current-voltage characteristics showgood photovoltaic response of the fabricated Ni/ZnSnS3/Ni device in the visible range indicating its application in PV devices and photodetector.

Tuning bandgap and controlling oxygen vacancy in BiFeO3 via Ba(Fe1/2Nb1/2)O3 substitution for enhanced bulk ferroelectric photovoltaic response in Al/BFO–BFN/Ag solar cell

Tuning bandgap and controlling oxygen vacancy in BiFeO3 via Ba(Fe1/2Nb1/2)O3 substitution for enhanced bulk ferroelectric photovoltaic response in Al/BFO–BFN/Ag solar cell

Photovoltaic Response of Liquid Phase Exfoliated Graphene - MoS2 Heterostructures

Photovoltaic Response of Liquid Phase Exfoliated Graphene - MoS₂ Heterostructures

Reconfigurable Vertical Phototransistor with MoTe2 Homojunction for High-Speed Rectifier and Multivalued Logical Circuits.

The most reported two-dimensional (2D) reconfigurable multivalued logic (RMVL) devices primarily involve a planar configuration and carrier transport, which limits the high-density circuit integration and high-speed logic operation. In this work, the vertical transistors with reconfigurable MoTe2 homojunction are developed for low-power, high-speed, multivalued logic circuits. Through top/bottom dual-gate modulation, the transistors can be configured into four modes: P-i-N, N-i-P, P-i-P, and N-i-N. The reconfigurable rectifying and photovoltaic behaviors are observed in P-i-N and N-i-P configurations, exhibiting ideal diode characteristics with a current rectification ratio over 105 and sign-reversible photovoltaic response with a photoswitching ratio up to 7.44 × 105. Taking advantage of the seamless homogeneous integration and short vertical channel architecture, the transistor can operate as an electrical switch with an ultrafast speed of 680 ns, surpassing the conventional p-n diode. The MoTe2 half-wave rectifier is then applied in high-frequency integrated circuits using both square wave and sinusoidal waveforms. By applying an electrical pulse with a 1/4 phase difference between two input signals, the RMVL circuit has been achieved. This work proposes a universal and reconfigurable vertical transistor, enabled by dual-gate electrostatic doping on top/bottom sides of MoTe2 homojunction, suggesting a high integration device scheme for high-speed RMVL circuits and systems.

Boosting the efficiency of an inverted structure halide perovskite solar cell: a numerical investigation

Inverted solar cells have attracted significant attention because they have low hysteresis and are resistant to environmental variables, such as oxygen and humidity, making them more stable and long-lasting. Herein, we investigate the performance optimisation of an inverted design based on MAPbI3-xClx with the structure ITO/PTAA/MAPbI3-xClx/PC60BM/BCP/Ag by utilising SCAPS-1D, a simulation tool. Accordingly, a substantial improvement in efficiency can be achieved by optimising several factors linked to each layer’s performance in a perovskite solar cell (PSC). Total defect density, work function, thickness, and electron affinity have a significant impact on the photovoltaic response. Specifically, the impact of optimisation of the charge transport layers and the perovskite layer on the device’s performance parameters was discussed, resulting in a milestone within a remarkable increase in PCE of 21.59%, whereas the original structure’s efficiency was 6.9%. Additionally, it has been shown that aluminium can substitute silver in the top electrode of a solar cell without affecting its efficiency, allowing the development of cost-effective solar cells. The present study provides an insight in the creation of a highly stable low-cost and higher-efficiency perovskite solar cell.

Ferroelectric, flexoelectric and photothermal coupling in PVDF-based composites for flexible photoelectric sensors.

A ferroelectric polyvinylidene fluoride (PVDF) film with excellent flexibility possesses great potential for photodetection and wearable devices. However, the relatively weak photo-absorption and the consequent small photocurrent limit its photofunctional properties. Herein, we embedded a strongly visible-light active material system, 0.5Ba(Zr0.08Ti0.8Mn0.12)O3-0.5(Ba0.7Ca0.3)TiO3 (BZTM-BCT) loaded with Ag and Au nanoparticles, into a PVDF film, which demonstrates a significantly higher photovoltaic response in the whole visible light range with a β-phase content of over 90%. In a state of "bending + poling", the PVDF/BZTM-BCT:Au film presents an optimal response for photoelectric properties by exhibiting a photocurrent that is 57 times higher than that of a pure PVDF film when illuminated with 405 nm LED light at 100 mW cm-2. Photoexcitation and thermal excitation jointly contribute to the generation of free carriers, while the flexoelectric and ferroelectric coupling electric field provides a greater driving force for carrier separation and transport. More interestingly, composite film-based photoelectric sensors can simultaneously respond to light and the movement and deformation of contacted things, indicating its potential in versatile applications. Overall, this work puts forward a new route for designing new flexible multifunctional photoelectric devices.