Perovskite Photovoltaic Cells Research Articles

The effects of crystal structure on the photovoltaic performance of perovskite solar cells under ambient indoor illumination

Organic-inorganic hybrid lead halide perovskite materials with the general formula MAPbI3-nBrn (n = 0, 1, 2, and 3) exhibiting a range of crystal structures and a wide range of optical bandgaps are explored for their potential to harvest energy from ambient light sources. The replacement of I− with Br− is found to transform the perovskite crystal structure from the tetragonal for MAPbI3 to the pseudo cubic for MAPbI2Br and MAPbIBr2 and cubic for MAPbBr3 while increasing the optical bandgap from 1.59 eV to 2.31 eV. Photovoltaic cells (PVCs) are constructed using these perovskites and are found to exhibit power conversion efficiencies (PCEs) of 29.83 (MAPbI3), 23.75 (MAPbI2Br), 21.47 (MAPbIBr2), and 19.94% (MAPbBr3) under LED light illumination (1000 lux; ~0.371 mW cm−2), with a record high open-circuit voltage (VOC) of 1.15 V being observed for the MAPbBr3. The effect of crystal structure variation on the charge carrier mobility, trap states, recombination losses, photovoltaic properties, and operational stabilities has been investigated systematically under indoor illumination. Overall, this work provides a clear vision on the influence of perovskite crystal structures upon the photovoltaic properties and shows a pathway to achieve high VOC in perovskite PVCs under low-intensity ambient light sources.

Perovskite Photovoltaic Cells: Synergistic Effect of Excited State Property and Aggregation Characteristic of Organic Semiconductor on Efficient Hole‐Transportation in Perovskite Device (Adv. Funct. Mater. 5/2021)

In article number 2007180, Tae Kyu Ahn, Sanghyuk Park, Hui Joon Park, and co-workers investigate the synergistic effect of the excited state property and aggregation behavior of organic semiconductors, enhancing hole-transportation in perovskite devices.

Effects of doping with Na, K, Rb, and formamidinium cations on (CH3NH3)0.99Rb0.01Pb0.99Cu0.01I3−x(Cl, Br)x perovskite photovoltaic cells

The effects of doping with alkali metals and formamidinium cations on CH3NH3(Rb)Pb(Cu)I3(Cl,Br) perovskite photovoltaic cells were investigated. Lattice constants were slightly decreased and increased by K and Na doping, respectively. This indicated that Na atoms occupied interstitial sites in the perovskite crystal. The conversion efficiencies for most of the devices decreased after one year. However, the conversion efficiency for the CH3NH3(Na,Rb)Pb(Cu)I3(Cl,Br) photovoltaic cell was unchanged after one year. The Na-doped perovskite provided the smallest carrier trap density, which suggested that lattice defects were suppressed by Na doping. First principles calculations supported these experimental results.

(Invited) Interfacial Engineering for High Voltage Performance of Perovskite Photovoltaic Cells

Since our first discovery of perovskite solar cell (PSC) in 2009, enormous efforts have been put into different aspects of PSCs and the progress has been incredibly fast on all fronts. The background, on-going R&Ds, and future direction of PSC research have been reported by our group as a comprehensive review.1 Although efficiency level has reached 25%, PSCs face serious challenges of practical stability and durability required for industrialization. Compositional engineering of lead halide perovskites by mixing different cations and anions, using modulator molecules and mixing 2D and 3D structures have improved the stability of perovskites against heat and moisture. However, organic cations in halide perovskites (methylammonium, etc.) and use of diffusible ionic dopants in hole transport materials (HTMs) are responsible for low stability of perovskites at high temperatures (>120oC). In this respect, use of all-inorganic perovskite materials and dopant-free HTMs is highly desired.2 We have conducted the device fabrication in this direction using CsPbI3 and CsPbI2Br as solution-processed perovskite films. The perovskite absorbers were made into junction with dopant-free HTMs to develop thermally stable PSCs.By chemical engineering to improve the quality of interfacial structure at the hetero-junction, all-inorganic and dopant-free PSCs yielded power conversion efficiency up to 15%. Further we could enhance the open-circuit voltage (Voc) of this PSC up to 1.42V, which is the highest Voc ever achieved with a single perovskite cell.3 In preparation of all-inorganic perovskites, a big challenge should also be directed to development of lead-free perovskite materials for environmental safety in practical applications.2 Among extensive applications of PSCs for outdoor and indoor power generation, use of PSCs in space environments is promising because thin perovskite photovoltaic films demonstrate high stability and tolerance against exposure to high energy particle irradiations (proton and electron beams).4 Thin absorbers (<500 nm) avoid accumulation of particles and due to intrinsic defect tolerant nature of perovskites, radiation-induced collision damage is highly suppressed. Our current efforts in making PSCs based on both lead and lead-free perovskites, and future perspectives of perovskite photovoltaics will be presented.

Performance Analysis of Planar Heterojunction Perovskite Solar Cell Featuring Double Hole Transport Layer &amp; Backplane

Perovskite photovoltaic cells have attracted appreciable importance from many researchers in the recent decade due to its reduced thickness, very less fabrication cost, and impressive photovoltaic performance. In this work, the authors investigated the simulation-based performance analysis of solar cells with perovskite CH3NH3PbI3 material. In the given paper authors have proposed the design of SnO2 (electron transport layer)/ CH3NH3PbI3 (active layer)/ SiGe and Spiro-OMeTAD (hole transport layers)/ SiGeSn (Backplane) based solar cell may be grown on the glass substrate. The simulation of the predicted device is compared with the already existing perovskite solar cell performance parameters and comparatively higher conversion efficiency was obtained for the proposed structure. In this proposed work, the consequence of perovskite layer thickness, different doping concentrations of perovskite (active) layer, hole transport layers (HTLs), Ge mole fraction of SiGe hole transport layer, hole mobility of Spiro-OMeTAD layer and backplanes on the characteristic performance of the proposed solar cell have been analyzed. The maximum conversion efficiency of 28.57% is reported for the given structure, having an amalgamation of two non-identical hole transport layers which ensures considerable photon conversion efficiency. Hence, this current work would propose a stepping stone in the advancement of high-performance perovskite photovoltaic cells in comparison with the pre-existing ones.

Degradation of perovskite solar cells by the doping level decrease of HTL revealed by capacitance spectroscopy

Degradation process of perovskite photovoltaic cells with Spiro-OMeTAD hole transport layer (HTL) has been monitored by means of capacitance spectroscopy. Detailed measurements of the capacitance as a function of the bias voltage revealed that the efficiency decline is accompanied by the doping level decrease of HTL at the perovskite interface. Together with the TOF-SIMS measurement, it is clearly demonstrated that one degradation mechanism is due to the diffusion of dopant in the HTL into the adjacent perovskite layer.

Synergistic Effect of Excited State Property and Aggregation Characteristic of Organic Semiconductor on Efficient Hole‐Transportation in Perovskite Device

AbstractIntrinsic characteristics of organic semiconductor‐based hole transport materials (HTMs) such as facile synthesizability, energy level tunability, and charge transport capability have been highlighted as crucial factors determining the performances of perovskite photovoltaic (PV) cells. However, their properties in the excited state have not been actively studied, although PVs are operated under solar illumination. Here, the characteristics of organic HTMs in their excited state such as transition dipole moment can be a decisive factor that can improve built‐in potential of PVs, consequently enhancing their charge extraction property as well as reducing carrier recombination. Moreover, the aggregation property of organic semiconductors, which has been an essential factor for high‐performance organic HTMs to improve their carrier transport property, can induce a synergistic effect with their excited state property for the high‐efficiency perovskite PVs. Additionally, it is also confirmed that their optical bandgaps, manipulated to have their absorption in the UV region, are beneficial to block UV light that degrades the quality of perovskite, consequently improving the stability of perovskite PV in p–i–n configuration. As a proof‐of‐concept, a model system, composed of triarylamine and imidazole‐based organic HTMs, is designed, and it is believed that this strategy paves a way toward high‐performance and stable perovskite PV devices.

Environmental Impact per Energy Yield for Bifacial Perovskite Solar Cells Outperforms Crystalline Silicon Solar Cells

A promising technology for the future of solar energy is the highly efficient bifacial photovoltaic (PV) cell using perovskite as an absorbing layer. Here we report the environmental impact per energy generated from bifacial perovskite PV cells in single- and multi-junction configurations. To determine the environmental performance of the energy provided from bifacial perovskites and compare it with the analogous monofacial structures, we develop a realistic energy yield (EY) model. According to our model, the studied bifacial structures show between 9% and 26% EY increase compared with monofacial cells among all surfaces and locations studied. For the environmental impact analysis, we use normalized cradle-to-end-of-use impact from single-junction crystalline silicon (c-Si) solar cells as a reference point. Our results show that there are opportunities for all studied bifacial perovskite PV structures to become more environmentally friendly than c-Si cells.

Defect-Passivating Organic/Inorganic Bicomponent Hole-Transport Layer for High Efficiency Metal-Halide Perovskite Device

In this work, we introduce a bicomponent hole-transport layer, composed of inorganic NiOx and a donor-acceptor-donor (D-A-D)-structured organic small molecule, for p-i-n planar perovskite photovoltaic (PV) cells. The newly designed D-A-D organic hole-transporting material (HTM), (4',4‴-(1,3,4-oxadiazole-2,5-diyl)bis(N,N-bis(4-methoxyphenyl)-[1,1'-biphenyl]-4-amine)), is shown to be an efficient HTM without a dopant, and methoxy functional units, further introduced to the molecules, are confirmed to be beneficial to passivate the defects in the perovskite, which improves the crystallinity of perovskite and suppresses the nonradiative recombination in the devices, consequently enhancing the performances of PV cells (over 20% efficiency from p-i-n architecture). Furthermore, the decreased defect sites along with the UV-blocking property of the HTM in p-i-n architecture are advantageous in improving the stability of the PV devices.

Air-stable perovskite photovoltaic cells with low temperature deposited NiOx as an efficient hole-transporting material

The electron-beam physical vapor deposition (EBPVD) technique was selected for nickel oxide (NiOx) film deposition at room temperatures. NiOx film (18 nm thick) was deposited as a hole transporting material (HTM) for inverted perovskite solar cells (PSCs) onto a fluorine-doped tin oxide (FTO)-coated glass substrate at a chamber vacuum pressure of 4.6×104 Pa. PSCs were fabricated as a glass/FTO/NiOx(HTM)/CH3NH3PbI3/PC61BM/BCP/Ag structure with as-deposited and annealed (500 °C for 30 min) NiOx films. Under 100 mW cm-2 illumination, as-deposited and annealed NiOx as HTM in PSCs (0.16 cm2) showed a high-power conversion efficiency (PCE) of 13.20% and 13.24%, respectively. The as-deposited and annealed PSCs retained 72.2% and 76.96% of their initial efficiency in ambient conditions, correspondingly. This study highlights the possibility of achieving highly crystalline and finely disseminated NiOx films by EBPVD for fabricating efficient inverted PSCs.

22% Efficiency Inverted Perovskite Photovoltaic Cell Using Cation-Doped Brookite TiO2 Top Buffer.

Simultaneously achieving high efficiency and high durability in perovskite solar cells is a critical step toward the commercialization of this technology. Inverted perovskite photovoltaic (IP‐PV) cells incorporating robust and low levelized‐cost‐of‐energy (LCOE) buffer layers are supposed to be a promising solution to this target. However, insufficient inventory of materials for back‐electrode buffers substantially limits the development of IP‐PV. Herein, a composite consisting of 1D cation‐doped TiO2 brookite nanorod (NR) embedded by 0D fullerene is investigated as a top modification buffer for IP‐PV. The cathode buffer is constructed by introducing fullerene to fill the interstitial space of the TiO2 NR matrix. Meanwhile, cations of transition metal Co or Fe are doped into the TiO2 NR to further tune the electronic property. Such a top buffer exhibits multifold advantages, including improved film uniformity, enhanced electron extraction and transfer ability, better energy level matching with perovskite, and stronger moisture resistance. Correspondingly, the resultant IP‐PV displays an efficiency exceeding 22% with a 22‐fold prolonged working lifetime. The strategy not only provides an essential addition to the material inventory for top electron buffers by introducing the 0D:1D composite concept, but also opens a new avenue to optimize perovskite PVs with desirable properties.

Three dimensional analysis of dye-sensitized, perovskite and monocrystalline silicon solar photovoltaic cells under non uniform solar flux

For low/high concentration, when the distribution of solar radiation is non-uniform over the surface of the solar cell, it gets heated up non-uniformly which affects the cell efficiency. Thus, in the present work, three dimensional analysis of the solar cells is carried out under non-uniform solar flux. It involves partial differential equations. For silicon cells, studies are available that use numerical techniques (involving iterations) to solve the differential equations. However, if the differential equations can be solved analytically, one can get an analytical expression for three dimensional non-uniform temperature distribution of the cell. The current work aims at it. Dye-sensitized (DSSC), perovskite and mono-Si cells are investigated. The effects of wind direction, its speed, inclination and solar irradiance on the three dimensional temperature distribution, heat losses and cell efficiency have been investigated. It is concluded that with increase in wind azimuthal from 0° to 90°, the efficiency decreases from 22.1% to 21.3% for mono-Si, 19.0% to 18.0% for perovskite and 12.0% to 11.9% for DSSC.

Effect of annealing on the efficiency of ambient-atmosphere fabricated MAPbI3 perovskite solar cells

We describe a novel and cost-effective method to enhance the photo-conversion efficiency of blended PbI2/TiO2 perovskite photovoltaic cells by pre-annealing the constituent film components during the fabrication. This approach is also unique because it does not presume a strictly controlled fabrication environment. The average conversion efficiencies of the cells of the final devices were observed to rise from 6.6% to 10.8% for annealing temperatures of 60 ∘C to 100 ∘C, respectively. Annealing improves the nanoparticle agglomeration in the perovskite film and hence the efficiency. The changes in the film morphology and the optical properties were confirmed using standard techniques.

Unprecedentedly high indoor performance (efficiency &gt; 34 %) of perovskite photovoltaics with controlled bromine doping

Abstract Indoor lighting-driven photovoltaic cells have significant potential for energy generation due to their ability to convert waste lighting into reusable sources and energy generation regardless of weather conditions. As a promising renewable source of energy, indoor perovskite photovoltaic cells possess the advantages of high efficiency, facile processability, and cost-effectiveness. Here, we propose stoichiometry-controlled perovskite-based photovoltaic cells illuminated under the dim light-emitting diode (LED) to capture and recycle the light sources. Among the various stoichiometric methods tested, 10% bromide-doped perovskite photoactive layers exhibit the best performance as a result of better crystallization and uniform surface. This helps to form larger grains of perovskite with reduced trap sites and defects, which suppresses carrier trapping and non-radiation recombination centers, resulting in improved device performance. Moreover, additional substitution by an appropriate halide increases the stability of the conventional perovskite by forming a pseudo-cubic phase. Consequently, the photovoltaic device examined under dim LED (1000 lx) indoor lighting exhibits an average power conversion efficiency of 34.5 ± 1.2%, which is superior by 18% compared with that of a control device (29.2 ± 1.6%). These results reveal the potential of indoor-driven perovskite photovoltaic cells as next-generation power sources which may pioneer the development of new types of indoor electronics.

How To Quantify the Efficiency Potential of Neat Perovskite Films: Perovskite Semiconductors with an Implied Efficiency Exceeding 28.

Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; however, in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination. Nevertheless, compared to GaAs and monocrystalline silicon PV, perovskite cells have significantly lower fill factors due to a combination of resistive and non-radiative recombination losses. This necessitates a deeper understanding of the underlying loss mechanisms and in particular the ideality factor of the cell. By measuring the intensity dependence of the external open-circuit voltage and the internal quasi-Fermi level splitting (QFLS), the transport resistance-free efficiency of the complete cell as well as the efficiency potential of any neat perovskite film with or without attached transport layers are quantified. Moreover, intensity-dependent QFLS measurements on different perovskite compositions allows for disentangling of the impact of the interfaces and the perovskite surface on the non-radiative fill factor and open-circuit voltage loss. It is found that potassium-passivated triple cation perovskite films stand out by their exceptionally high implied PCEs > 28%, which could be achieved with ideal transport layers. Finally, strategies are presented to reduce both the ideality factor and transport losses to push the efficiency to the thermodynamic limit.

Economically Sustainable Growth of Perovskite Photovoltaics Manufacturing

Summary The significant capital expense of photovoltaics manufacturing has made it difficult for new cell and module technologies to enter the market. We present two technoeconomic models that analyze the sustainable growth of perovskite manufacturing for an R2R single-junction technology and a perovskite-silicon tandem module, focusing on the impacts of economies of scale and average selling price on profitability. We establish a cost range of $3.30/W to $0.53/W for flexible modules manufactured in factory sizes ranging from 0.3 MW/year to 1 GW/year. In addition, we model the cost to manufacture a tandem module consisting of a single-junction perovskite cell stacked in 4-terminal configuration onto a silicon cell and show how an existing manufacturer can grow at a faster rate by co-investing in tandems. Our analyses highlight potential routes to market for perovskite photovoltaics and the possibility to sustainably grow a photovoltaics manufacturing company even in markets with higher labor rates.

Study on photovoltaic stability and performance by incorporating tetrabutyl phosphonium iodide into the active layer of a perovskite type photovoltaic cell.

A simple synthesis of an ionic liquid is carried out using a trialkylphosphine and an alkyl halide. The results showed that the quality of perovskite crystals is enhanced by the incorporation of B4PI, when the percentage is 1.5% the PCE of champion PSCs MA98.5(B4PI)1.5PbI3 increases significantly from 15.5%, with a VOC of 0.957 mV, JSC of 23.6 mA cm−2, and an FF of 68.4%. Stability tests show that excess B4PI by 20% has a protective effect against humidity, MA80(B4PI)20PbI3 was more stable towards humidity, losing only 20% efficiency for 200 h.

All-self-metered solution-coating process in ambient air for the fabrication of efficient, large-area, and semitransparent perovskite solar cells

Large-area semitransparent MAPbI3 perovskite photovoltaic cells with fully self-metered horizontal-dip-coated functional layers fabricated in air.

Interfacial and structural modifications in perovskite solar cells.

The rapid and continuous progress made in perovskite solar cell (PSC) technology has drawn considerable attention from the photovoltaic research community, and the application of perovskites in other electronic devices (such as photodetectors, light-emitting diodes, and batteries) has become imminent. Because of the diversity in device configurations, optimization of film deposition, and exploration of material systems, the power conversion efficiency (PCE) of PSCs has been certified to be as high as 25.2%, making this type of solar cells the fastest advancing technology until now. As demonstrated by researchers worldwide, controlling the morphology and defects in perovskite films is essential for attaining high-performance PSCs. In this regard, interface engineering has proven to be a very efficient way to address these issues, obtaining better charge collection efficiency, and reducing recombination losses. In this review, the interfacial modification between perovskite films and charge-transport layers (CTLs) as well as CTLs and electrodes of PSCs has been widely summarized. Grain boundary (GB) engineering and stress engineering are also included since they are closely related to the improvement in device performance and stability.

Precursor vapor deposited perovskite solar cells with smooth absorber layer

Preparation of a smooth methylammoniumleadiodide (CH3NH3PbI3) perovskite absorber film is one of the most critical processes in fabricating a perovskite photovoltaic cell with high efficiency. In this study, we report an original coating method to prepare CH3NH3PbI3 films by using the solvent vapors of precursor methylamine (MA) and hydroiodic acid (HI) solutions on lead (II) iodide (PbI2) thin films. In this strategy, the vapors of MA and HI solutions were briefly treated to the PbI2 coated substrate and then the resultant film was annealed to obtain smooth perovskite thin layer. After the topographic analyses of the thin films, the surface roughnesses of the perovskite films were found to be limited by the surface roughnesses of the PbI2 films before precursor vapor exposure. Another important aspect of our approach is that there is no need to synthesize methylammonium iodide (CH3NH3I) salt for active layer preparation. Furthermore, this method enables large-area fabrication of high quality films by a very simple and brief process. After the characterization of preliminary devices with this method, we obtained a short circuit current density of 14.67 mA/cm2, an open circuit voltage of 0.815 V, a fill-factor of 0.59, and a power conversion efficiency of 7.08%.