Hybrid Organic-inorganic Solar Cells Research Articles

Effect of the Electron Transport Layer on the Photovoltaic Properties of Hybrid Organic Inorganic Perovskites Solar Cells: Cross-Section of Optics, Morphology, Composition and Quality

Ever since their dawn in 2009 1, hybrid organic–inorganic perovskite materials have been experiencing an ever increase in research investment to finally emerge as a strong alternative for high power conversion efficiency (PCE) photovoltaic devices at low costs. One of the main challenges that is currently impeding the upscaling of these solar cells is the phenomenon of hysteresis on their j–V response that has been correlated with slow ion migration which, in turn, affects their photovoltaic properties. Although hysteresis has been described to some extent of detail, the precise role of the external contacts remains under debate. Furthermore, there has been a great deal of focus on materials and interface design while less attention has been given to optical aspects of these cells. Our work highlights the role of electron transport layer (ETL) of different compositions and synthesized through various routes on the hysteresis response of these systems. We show that there’s a clear correlation between thickness, morphology and composition of the ETL on the photovoltaic response these systems. To better elucidate such a response, we have utilized photoluminescence, electroluminescence, absorption and kelvin probe force microscopy to get a substantial grasp of the optoelectronic phenomena occurring at the interfaces in perovskite solar cells.Acknowledgments: This research was supported by a Hydro-Quebec/NSERC CRD grant and the McGill Sustainability Systems Initiative (MSSI).1- Kojima, A., Teshima, K., Shirai, Y. and Miyasaka, T., 2009. Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. Journal of the American Chemical Society, 131(17), pp.6050-6051.

A trilayered organic-inorganic hybrid perovskite material with low bandgap

A lead(II) organic-inorganic hybrid perovskite material [(TMA)2(MA)2Pb3I10] (1) has been synthesized by reactions of 2-thienylmethylamine (TMA) and methylamine (MA) with PbI2 in HI/H3PO2 aqueous solution. The crystallographic diffraction indicated the inorganic moiety in 1 is a trilayered perovskite structure constructed with [PbI6] octahedra, and the two organic amines are located between the inorganic layers, or embedded in the octahedral cavity of inorganic layers. The solid UV–vis absorption peak of compound 1 is located at 600 nm, and the bandgap calculated by DFT is 1.60 eV, both indicating it is a semiconductor and has potential application in organic-inorganic hybrid solar cell.

Polarization-enhanced photoelectric performance in a molecular ferroelectric hexane-1,6-diammonium pentaiodobismuth (HDA-BiI5)-based solar device

Molecular ferroelectric HDA-BiI5 has been utilized as the light-absorbing layer for organic-inorganic hybrid solar cells.

Recent Advances in the Chemistry and Synthesis of Thienopyrazine, Pyrrolopyrazine and Furopyrazine Derivatives

Bicyclic compounds derived from pyrazine and aromatic five-membered heterocycles including thiophene, furan and pyrrole show various biological and pharmacological proBicyclic compounds derived from pyrazine and aromatic five-membered heterocycles including thiophene, furan and pyrrole show various biological and pharmacological properties, such as anti-inflammatory, antiviral, antitumor, antioxidant, antimycobacterial, and cytostatic activities. In many cases, it has been demonstrated that there are more potent cytostatic and cytotoxic agents against human tumor cell lines, leukemia, colon cancer, central nervous system cancer, melanoma, ovarian cancer, prostate cancer and breast cancer. They are also useful precursors for the large scale preparation of inorganicorganic hybrid solar cells, suitable acceptors for the synthesis of low-band gap polymers. They use ligands for serotoninergic 5-HT7 receptor and are effective in neurogical and psychiatric diseases, antimalarial, neuroleptic and cardiovascular. The absence of any useful review concerning the chemistry and synthesis of the above-mentioned heterocyles encouraged us to underscore the recent advances in chemistry and synthetic approaches leading to the preparation of thienopyrazines, pyrrolopyrazines and furopyrazines since 1990.perties such as anti-inflammatory, antiviral, antitumor, antioxidant, antimycobacterial, and cytostatic activities. In many cases, it has been demonstrated that they are much more potent cytostatic and cytotoxic agents against human tumor cell lines, leukemia, colon cancer, central nervous system cancer, melanoma, ovarian cancer, prostate cancer and breast cancer. They also are useful precursors for the large scale preparation of inorganic-organic hybrid solar cells, suitable acceptors for the synthesis of low-band gap polymers. They use as ligands for serotoninergic 5-HT7 receptor and being effective in neurogical and psychiatric diseases, antimalarial, neuroleptic and cardiovascular. Due to the absence of any useful review concerning the chemistry and synthesis of the above-mentioned heterocyles encouraged us to underscore the recent advances in the chemistry and synthetic approaches leading to preparation of thienopyrazines, pyrrolopyrazines and furopyrazines from 1990 up to date.

Ti doped Sb2S3 thin film for improved performance of inorganic-organic hybrid solar cells

The inorganic-organic hybrid solar cells based on Ti doped antimony sulfide (Ti:Sb2S3) was prepared by a simple spin-castingmethod. Compared with that of the devices with the pristine Sb2S3, the power conversion efficiency (PCE) of the devices based on Ti:Sb2S3 was increased by 41%. The different Ti doping concentration impact on the performance of the devices was investigated. PCE of the cells was improved with Ti doping concentration increased until Ti concentration exceeds 6%, the highest PCE reaches to 2.70%. The better performance of the devices based on Ti:Sb2S3 is due to the improved optical absorption, and the decreased dangling bonds on the surface of the Ti:Sb2S3 thin film.

Phenomenological morphology design of hybrid organic-inorganic perovskite solar cell for high efficiency and less hysteresis

In this report, a modeling approach is employed to study the effect of the grain boundaries (GBs) and their electronic activity on the performance parameters of the perovskite solar cells (PSCs). Our model is based on the 1- dimensional drift-diffusion framework to engage the electron (hole) defects formed in the GBs and the GB's location through the perovskite layer. Power conversion efficiency (PCE) of the PSC is optimized with regards to the perovskite layer thickness, GBs location and perovskite layer band offset with GBs layer. The results shows that the location or the distribution of the GBs can vary the PCE of PSCs from 12% to around 21%, thereby making proper morphology engineering and passivation of GBs is a chief requirement for achieving high efficiency. PCEs larger than 21% require GB defect densities below 1015cm−2. It is demonstrated that the band offset of about 100 meV with GB width of 1 nm could effectively suppress the negative impact of the GBs throughout the entire perovskite layer. Interestingly, GBs location at closer points to electron transport layer (ETL)/perovskite interface may give rise to higher PCEs, however, relatively stronger hysteresis in current values is observed. The results here provide insight into the effect of the GBs location and their corresponding type of defects on the hysteresis and the PSC performance and opens up new horizons to find solutions for current PSC's shortcomings.

Fabrication of an Efficient Planar Organic-Silicon Hybrid Solar Cell with a 150 nm Thick Film of PEDOT: PSS

Organic–inorganic hybrid solar cells composed of p-type conducting polymer poly (3,4-ethylene-dioxythiophene): polystyrenesulfonate (PEDOT: PSS) and n-type silicon (Si) have gained considerable interest in recent years. From this viewpoint, we present an efficient hybrid solar cell based on PEDOT: PSS and the planar Si substrate (1 0 0) with the simplest and cost-effective experimental procedures. We study and optimize the thickness of the PEDOT: PSS film to improve the overall performance of the device. We also study the effect of ethylene glycol (EG) by employing a different wt % as a solvent in the PEDOT: PSS to improve the device’s performance. Silver (Ag) was deposited by electron beam evaporation as the front and rear contacts for the solar cell device. The whole fabrication process was completed in less than three hours. A power conversion efficiency (PCE) of 5.1%, an open circuit voltage (Voc) of 598 mV, and a fill factor (FF) of 58% were achieved.

Multiscale modeling of active layer of hybrid organic-inorganic solar cells for photovoltaic applications by means of density functional theory and integral equation theory of molecular liquids

Photovoltaic devices convert solar energy into electricity and are promising candidates to reduce carbon emission while providing an alternative way to meet increasing demand in energy consumption. In recent years, organic or hybrid organic-inorganic photovoltaic devices demonstrate steady increase in performance and stability and a promising tendency toward the low production cost. To make them attractive for commercial production, however, a deep understanding and ability to predict physical, chemical and electrochemical processes occurring in photovoltaic conversion layer is needed. Here, we present multiscale modeling of electronic and structural properties of hybrid organic-inorganic perovskites (OIP) of the type CH3NH3PbX3, X = Br, Cl, I, in contact with organic molecules of P3BT, P3HT, or SQ02, including adsorption on inorganic substrates of TiO2. Our methodology is based on Density Functional Theory (DFT) and integral equation theory of molecular liquids in the Reference Interaction Site Model (RISM). We apply it to study the photovoltaic thin film nanomorphology and determine the key factors affecting the performance of OIP-based bulk heterojunction solar cells through their influence on charge separation, charge transport and recombination losses in donor-acceptor blends. These factors include chemical composition of heterojunctions and mutual orientation of molecules on the border of the donor-acceptor or donor-acceptor-substrate systems. Since the formation of thin active layer of solar cells occurs in fluidic phase, we also provide a detailed microscopic insight into the organization of solvent molecules in the solvation shell structure and their contribution to the solvation thermodynamics. In total, these properties define charge transfer processes from donor to acceptor and are utilized in development of new generation organic and hybrid organic-inorganic solar cells. The calculated nanoscale morphologies serve as a guide in rational design of organic or hybrid photovoltaics.

(Invited) (AgIn)xZn2(1-x)S2 Quantum Dots with ZnO or TiO2 for Inorganic/Organic Hybrid or Metal Halide Perovskite Solar Cells

Nanoparticles made of metal sulfides as quantum dots (QDs) have been prepared as electron transporting, light harvesting, and/or stabilizing parts for solar cells to improve their photovoltaic performance and durability. (AgIn)xZn2(1-x)S2 with its band gap in the range from 1.8 eV to 2.2 eV [1,2] has attractive potentials as the light absorber and the fluorescent material [3-5]. It was also found that the annealing of (AgIn)xZn2(1-x)S2 film at 500 ˚C in air brought the improvement of charge mobilities up to around 6.0 cm2 V-1 s-1[1,6]. In this context, preparation and band gap tuning of (AgIn)xZn2(1-x)S2 QDs through mixing with ZnO or TiO2 as the electron transport layer for inorganic-organic hybrid solar cells or metal halide perovskite solar cells (PSCs) have been investigated. Monodispersed AgInS2 [viz. x = 0 in (AgIn)xZn2(1-x)S2] QDs with an average value of the diameter of 6.22 ± 0.79 nm were prepared according to the reported procedures [7]. The interplanar spacing of the QDs was 0.33 nm, which corresponds to (112) crystal planes of the tetragonal phase of AgInS2. Introduction of AgInS2 QDs into hybrid solar cells resulted in over doubled enhancement of the photocurrent generation from 400 nm to 450 nm and the improvement of power conversion efficiencies (PCEs) as twice as the device without AgInS2 QDs [8]. While PSCs have been attracting many researchers because of their outstanding photophysical properties for photovoltaic performance. Development of the electron (or hole) transport layer of planar PSCs is one of the most important keys to improve the photovoltaic performance and the stability. Accordingly, development of hole transport layers by using various conjugated polymers for PSCs have been reported [9]. TiO2 and TiO2 mixed with AgInS2 QDs as dual electron transport layers were also introduced in PSCs in order to improve the photovoltaic performance and the stability. To prepare a decent physical contact between the electron transport layer and the rough surface of fluorine doped tin oxide, convective deposition technique was adopted because it has previously been confirmed that this method is one of the effective solution-based coating methods to deposit some self-assembled monolayer of both micro- and nanoparticles [10]. It was found that the addition of AgInS2 into TiO2 reduced pinholes at the interspace of the grains of the TiO2, enhanced a rectification ratio of the planar PSCs and improved the efficiency of the electron extraction from the active layer of metal halide perovskite through the TiO2/TiO2:AgInS2 QDs electron transport layer. PCE of the device was increased from 16.3% to 17.5% by the TiO2/TiO2:AgInS2 QDs (1.6 mg mL-1) as dual electron transport layers. The device with the dual electron transport layers showed the improvement of the external quantum efficiency in the wavelength region from 300 nm to 750 nm as compared with that of the device with TiO2 single layer. This result probably caused by the enhancement of light harvesting by AgInS2 QDs and the enhancement of the charge transfer from the perovskite layer to the dual electron transport layers. The long-term stability of the PSCs with the dual electron transport layers was confirmed when 1.6 mg mL-1 of AgInS2 was added, which was followed by the encapsulation and improvement of the retained PCE after the storage of the device in air for 15 days from 11% to 34% was also observed. This result implies that the TiO2/TiO2:AgInS2 QDs as dual electron transport layers not only brought the improvement of photovoltaic performance but also the durability. [1] Akaki, Y.; Kurihara, S.; Shirahama, M.; Tsurugida, K.; Seto, S.; Kakeno, T.; Yoshino, K. J. Phys. Chem. Solids. 2005, 66, 1858-1861. [2] Liu, B.; Li, X.; Zhao, Q.; Ke, J.; Tadé, M.; Liu, S. Appl. Catal., B 2016, 185, 1-10. [3] Kim, J.-H.; Lee, K.-H.; Jo, D.-Y.; Lee, Y.; Hwang, J. Y.; Yang, H. Appl. Phys. Lett. 2014, 105, 133104. [4] Shen, T.; Bian, L.; Li, B.; Zheng, K.; Pullerits, T.; Tian, J. Appl. Phys. Lett. 2016, 108, 213901. [5] Jasieniak, J.; Califano, M.; Watkins, S. E. ACS Nano. 2011, 5, 5888-5902. [6] Akaki, Y.; Kurihara, S.; Shirahama, M.; Tsurugida, K.; Kakeno, T.; Yoshino, K. J Mater Sci: Mater Electron 2005, 16, 393-396. [7] Torimoto, T.; Adachi, T.; Okazaki, K.-i.; Sakuraoka, M.; Shibayama, T.; Ohtani, B.; Kudo, A.; Kuwabata, S. J. Am. Chem. Soc. 2007, 129, 12388-12389. [8] Kim, E.-M.; Ruankham, P.; Lee, J.-H.; Hachiya, K.; Sagawa, T. Jpn. J. Appl. Phys. 2016, 55, 02BF06. [9] Ruankham, P.; Sagawa, T. J Mater Sci: Mater Electron 2018, 29, 9058-9066. [10] Kaewprajak, A.; Kumnorkaew, P.; Sagawa, T. Org. Electron. 2018, 56, 16-26.

Advantages of adding just enough alkalis

Solar Cells For organic-inorganic hybrid solar cells, addition of cesium or rubidium cations can improve power conversion efficiency. Correa-Baena et al. used nanoscale x-ray fluorescence imaging to show that the addition of metal cations at low concentrations homogenized the distribution of bromide and iodide anions and also increased charge-carrier lifetimes. However, at high concentrations, aggregation and cluster formation led to increased charge recombination. Science , this issue p. [627][1] [1]: /lookup/doi/10.1126/science.aah5065

Homogenized halides and alkali cation segregation in alloyed organic-inorganic perovskites.

The role of the alkali metal cations in halide perovskite solar cells is not well understood. Using synchrotron-based nano-x-ray fluorescence and complementary measurements, we found that the halide distribution becomes homogenized upon addition of cesiumiodide, either alone or with rubidiumiodide, for substoichiometric, stoichiometric, and overstoichiometric preparations, where the lead halide is varied with respect to organic halide precursors. Halide homogenization coincides with long-lived charge carrier decays, spatially homogeneous carrier dynamics (as visualized by ultrafast microscopy), and improved photovoltaic device performance. We found that rubidium and potassium phase-segregate in highly concentrated clusters. Alkali metals are beneficial at low concentrations, where they homogenize the halide distribution, but at higher concentrations, they form recombination-active second-phase clusters.

Photovoltaic characteristics of (E-Admantan fulgide thin film/P-Si single crystal) solar cell

A hybrid organic-inorganic solar cell (HOISc) has prepared by thermal evaporation of a thin film of {E-Adamantan-2-Ylidene - 4-[1 - (2, 5-dimethyl-3furyl) ethyldene] dihydro-2,5-Furandione} as a new member of the Fulgides’ family, on a single crystal of a p-type silicon wafer (P-Si). The analysis of the dark current, voltage characteristics suggested the presence of two conduction mechanisms; thermo-ionic assisted tunnelling mechanism followed by space charge limited current (SCLC) mechanism, which dominated by a single trap level. The reverse current was interpreted regarding either Pool-Frenkel or Schottky - effect. The dark, evacuated capacitance-voltage characteristic at room temperature exhibited an abrupt nature with a built-in voltage Vbi ≈ 0.26 Volt. The width of the depletion region,W ≈ 2.22 μm. The analysis of the photovoltaic characteristic at room temperature and under illumination of (23.56 mW cm−2) helped in the determination of some solar cell parameters such as; the open circuit voltage, VOC = 0.75 V, the fill factor, FF = 0.47 and the efficiency of the cell, η ≈ 6.892%.

Interfacial evolution of AgBiS2 absorber layer obtained by SILAR method in hybrid solar cells

AgBiS2 is a promising and environmentally friendly absorber material for use in hybrid solar cells (HSC). Here, we report a study on the evolution of interfacial phenomena observed during deposition of AgBiS2 onto mesoporous TiO2 by the two-stage successive ionic layer adsorption-reaction method. With this approach, inorganic–organic HSC were assembled using Co2+ doped P3HT as hole transport layer. Surface photovoltage spectroscopy and contact potential difference measurements corroborated a low density of trap states in the ternary chalcogenide and lack of majority carrier barriers, compared to the binary absorbers used as reference. The best HSC exhibits a power conversion efficiency of 2.87% under irradiation of 100 mW cm−2, which is attractive for an easily scalable, no capping, no passivating synthesis of AgBiS2.

Recent Progress in the Design and Synthesis of Nitrides for Mesoscopic and Perovskite Solar Cells

With growing concerns about global warming and the energy crisis, a variety of photovoltaic devices have attracted worldwide attention as alternative energy sources. Among them, organic-inorganic hybrid photovoltaics, typically mesoscopic and perovskite solar cells, are promising, owing to their potential for low-cost energy production, which mainly comes from unlimited combinations of materials optimized for each step of solar energy conversion. However, the commercialization of organic-inorganic hybrid solar cells is hampered by costly electrocatalysts or hole-transport materials. Currently, state-of-the-art dye- or quantum-dot-sensitized solar cells and perovskite solar cells necessitate noble metals and high-price polymeric materials. In an attempt to resolve this issue, various kinds of metal compounds have been investigated, and nitrides have been actively reported to possess a number of favorable properties for the aforementioned purpose, such as excellent electrical conductivity and superb electrocatalytic performance. Herein, the use of nitrides as cost-effective electrocatalysts or hole-transport materials in organic-inorganic hybrid solar cells is reviewed. Nitrides with a variety of morphologies and scales are discussed, together with the synergistic effect in the case of diverse composites. In addition, prospects and challenges for applying nitride materials are briefly suggested.

Improved silicon/PEDOT:PSS core/shell nanowire hetero-junction for organic–inorganic hybrid solar cells

In this work, we describe an improved silicon/organic conducting polymer (PEDOT:PSS) core/shell nanowire hetero-junction through increasing the work function of the PEDOT:PSS for organic–inorganic hybrid solar cells. The resultant devices exhibit an enhanced open-circuit voltage and power conversion efficiency. Through analysis of the dark current density versus voltage curves, the enhanced open-circuit voltage can be attributed to the lower reverse saturation current density, which is induced by the high work function PEDOT:PSS. These results provide an effective strategy for improving the open-circuit voltage and power conversion efficiency of silicon-based core/shell nanowire solar cells.

Significance of hydrogen bonding and other noncovalent interactions in determining octahedral tilting in the CH3NH3PbI3 hybrid organic-inorganic halide perovskite solar cell semiconductor

The CH3NH3PbI3 (methylammonium lead triiodide) perovskite semiconductor system has been viewed as a blockbuster research material during the last five years. Because of its complicated architecture, several of its technological, physical and geometrical issues have been examined many times. Yet this has not assisted in overcoming a number of problems in the field nor in enabling the material to be marketed. For instance, these studies have not clarified the nature and type of hydrogen bonding and other noncovalent interactions involved; the origin of hysteresis; the actual role of the methylammonium cation; the nature of polarity associated with the tetragonal geometry; the unusual origin of various frontier orbital contributions to the conduction band minimum; the underlying phenomena of spin-orbit coupling that causes significant bandgap reduction; and the nature of direct-to-indirect bandgap transition features. Arising from many recent reports, it is now a common belief that the I···H–N interaction formed between the inorganic framework and the ammonium group of CH3NH3+ is the only hydrogen bonded interaction responsible for all temperature-dependent geometrical polymorphs of the system, including the most stable one that persists at low-temperatures, and the significance of all other noncovalent interactions has been overlooked. This study focussed only on the low temperature orthorhombic polymorph of CH3NH3PbI3 and CD3ND3PbI3, where D refers deuterium. Together with QTAIM, DORI and RDG based charge density analyses, the results of density functional theory calculations with PBE with and without van der Waals corrections demonstrate that the prevailing view of hydrogen bonding in CH3NH3PbI3 is misleading as it does not alone determine the a−b+a− tilting pattern of the PbI64− octahedra. This study suggests that it is not only the I···H/D–N, but also the I···H/D–C hydrogen/deuterium bonding and other noncovalent interactions (viz. tetrel-, pnictogen- and lump-hole bonding interactions) that are ubiquitous in the orthorhombic CH3NH3PbI3/CD3ND3PbI3 perovskite geometry. Their interplay determines the overall geometry of the polymorph, and are therefore responsible in part for the emergence of the functional optical properties of this material. This study also suggests that these interactions should not be regarded as the sole determinants of octahedral tilting since lattice dynamics is known to play a critical role as well, a common feature in many inorganic perovskites both in the presence and the absence of the encaged cation, as in CsPbI3/WO3 perovskites, for example.

COMPARATIVE STUDY OF TiO2 AND ZnO APPLICATION IN HYBRID SOLAR CELLS USING COPOLYMER P3OT/P3MT

Hybrid inorganic-organic solar cells are an attractive alternative energy source because of their low-cost production and ability to make use of a large amount of solar radiation available. This work aims to evaluate different solar cells composed of TiO2 and ZnO with P3OT/P3MT copolymer. Layers of semiconductor oxides were deposited on transparent fluorine-doped tin oxide (FTO) by spin coating and adsorption in the polymer solution. X-ray diffraction (XRD), scanning electron microscopy (SEM), were used to characterize the fabricated semiconductors and curves of current density vs. potential (j-V), photochronoamperometry (j-t) and electrochemical impedance spectroscopy (EIS) were used to determine their electrical characteristics. The XRD analyses confirmed the crystalline nature of the oxide materials. SEM micrographs showed the spherical morphology of ZnO and the poorly defined agglomerate morphology of TiO2. The electrochemical measurements proved that the best cell was produced with P3OT/P3MT copolymer and TiO2, owing to its lower charge transfer resistance, with the following photovoltaic parameters: Voc = 0.615 V ± 0.004, jsc = 1.545 mA cm-2 ± 0.240, FF = 0.637 ± 0.003, and η = 0.617% ± 0.117.

High-Performance Fused Ring Electron Acceptor-Perovskite Hybrid.

We report the fused ring electron acceptor (FREA)-perovskite hybrid as a promising platform to fabricate organic-inorganic hybrid solar cells with simple preparation, high efficiency, and good stability. The FREA-perovskite hybrid films exhibit larger grain sizes and stronger crystallinity than the pristine perovskite films. Moreover, the FREA molecules can form coordination bonding with undercoordinated Pb atoms and passivate the trap states in the perovskite films. Time-resolved photoluminescence and transient absorption measurements reveal that FREA facilitates efficient electron extraction and collection. Transient photocurrent and photovoltage measurements suggest faster charge transfer and reduced charge recombination in solar cells based on FREA-perovskite hybrid films. Consequently, solar cells based on FREA-perovskite hybrid films yield a champion efficiency of 21.7% with enhanced stability, which is higher than that of the control devices based on pristine perovskite films (19.6%).

Interface engineering of G-PEDOT: PSS hole transport layer via interlayer chemical functionalization for enhanced efficiency of large-area hybrid solar cells and their charge transport investigation

In this study, in order to minimize the recombination current of free charge carriers in a large-area organic-inorganic hybrid solar cell (O-IHSCs), we improved the electrical conductivity of a graphene (G) and poly(3,4-ethylenedioxy thiophene)–poly(styrenesulfonate) (G-PEDOT:PSS) hole transport layer (HTL) by introducing various concentrations of synthesized graphene (G) into poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The electrical conductivity of G-PEDOT:PSS was enhanced to 932781.17 S m−1 via the addition of 2 mg/mL of G to PEDOT:PSS. The O-IHSCs fabricated with the highly conductive G-PEDOT:PSS composite as HTL enhanced the power conversion efficiency (PCE) to 3.90%, a 70% increase compared to O-IHSCs fabricated with pristine PEDOT:PSS HTL. However, the accumulation of G at a higher concentration (2.5 mg/mL) degrades the performance of the solar cell, which generated further defects or film aggregation, interfering with the fast transport of free charge carriers toward their respective electrodes. The G-PEDOT:PSS composite contained various types of functionalization via interfacial reaction between the G and PEDOT:PSS based on Raman and X-ray photoelectron spectroscopy studies. These chemical functionalizations provide an additional mechanism of charge transport via bridges enhancing the carrier mobility and suppression of recombination of free charge carriers, resulting in significant improvement in photovoltaic performance of the O-IHSCs.

Molecular Photon Upconversion Solar Cells Using Multilayer Assemblies: Progress and Prospects.

Molecular photon upconversion via triplet-triplet annihilation (TTA-UC) is an intriguing strategy to increase solar cell efficiencies and surpass the Shockley-Quiesser (SQ) limit. In this Perspective, we recount our group's efforts to harness TTA-UC by directly incorporating metal ion linked multilayers of acceptor and sensitizer molecules into an organic-inorganic hybrid solar cell architecture. These self-assembled multilayers facilitate both upconverted emission and photocurrent generation from the upconverted state with a record contribution of 0.158 mA cm-2 under 1 sun solar flux. We recount the progression toward this record and the mechanistic insights learned along the way, summarize the rate- and efficiency-limiting events, and outline improvements that must be made to produce a viable TTA-UC solar cell that can surpass the SQ limit. We also discuss the potential impact that efficient TTA-UC and photocurrent generation could have on existing record solar cells.