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Abstract: An encapsulation system comprising of a UV‐curable epoxy, a solution processed polymer interlayer, and a glass cover‐slip, is used to increase the stability of methylammonium lead triiodide (CH3NH3PbI3) perovskite planar inverted architecture photovoltaic (PV) devices. It is found this encapsulation system acts as an efficient barrier to extrinsic degradation processes (ingress of moisture and oxygen), and that the polymer acts as a barrier that protects the PV device from the epoxy before it is fully cured. This results in devices that maintain 80% of their initial power conversion efficiency after 1000 h of AM1.5 irradiation. Such devices are used as a benchmark and are compared with devices having initially enhanced efficiency as a result of a solvent annealing process. It is found that such solvent‐annealed devices undergo enhanced burn‐in and have a reduced long‐term efficiency, a result demonstrating that initially enhanced device efficiency does not necessarily result in long‐term stability. [ABSTRACT FROM AUTHOR]

Carrier transport in methylammonium lead iodide (MAPbI3)-based hybrid organic-inorganic perovskites (HOIPs) is obscured by vacancy-mediated ion migration. Thus, the nature of migrating species (cation/anion) and their effect on electronic transport in MAPbI3 has remained controversial. Temperature-dependent pulsed voltage-current measurements of MAPbI3 thin films are performed under dark conditions, designed to decouple ion-migration/accumulation and electronic transport. Measurement conditions (electric-field history and scan rate) are shown to affect the electronic transport in MAPbI3 thin films, through a mechanism involving ion migration and accumulation at the electrode interfaces. The presence of thermally activated processes with distinct activation energies ( Ea) of 0.1 ± 0.001 and 0.41 ± 0.02 eV is established, and are assigned to electromigration of iodine vacancies and methylammonium vacancies, respectively. Analysis of activation energies obtained from electronic conduction versus capacitive discharge shows that the electromigration of these ionic species is responsible for the modification of interfacial electronic properties of MAPbI3, and elaborates previously unaddressed issues of 'fast' and 'slow' ion migration. The results demonstrate that the intrinsic behavior of MAPbI3 material is responsible for the hysteresis of the solar cells, but also have implications for other HOIP-based devices, such as memristors, detectors, and energy storage devices. [ABSTRACT FROM AUTHOR]

Review: 72 refs. [ABSTRACT FROM AUTHOR]

Vacancy-ordered Cs 2 SnI 6 perovskite as an efficient light harvester sandwiched between the n -ZnO electron transport layer (ETL) and different p-type metal oxides, namely CuBi 2 O 4 , Cu 2 O, CuAlO 2 , and NiO, hole transport layers (HTL) with device architecture of FTO/ZnO/Cs 2 SnI 6 /HTL/Au, a lead-free all inorganic double perovskite solar cells. [Display omitted] • Eco-friendly all inorganic double perovskite solar cells (DPSCs). • Cs 2 SnI 6 double perovskite light harvester and metal oxide charge transport layer. • Ambient stable and highly efficient device with efficiency ∼ 30 %. • Theoretical modelling using SCAPS-1D for high efficiency DPSCs. Non-toxic and air-stable Cesium tin (IV) halide (Cs 2 SnI 6) is a promising alternative to lead halide perovskite for photovoltaic applications. This study reports the extensive analysis of vacancy-ordered Cs 2 SnI 6 perovskite as an efficient light harvester sandwiched between the n -ZnO electron transport layer (ETL) and different p-type metal oxides, namely CuBi 2 O 4 , Cu 2 O, CuAlO 2 , and NiO, hole transport layers (HTL), using SCAPS-1D software. Various physical parameters, viz. thickness, defect density (bulk and interfacial), and charge carrier concentration of different layers for the device architecture of FTO/ZnO/Cs 2 SnI 6 /HTL/Au, are systematically investigated along with the effect of parasitic resistance, work function, and operating temperature in the quest for best device performance in terms of photoconversion efficiency (PCE). The effect of DC biasing voltage is analyzed using C-V characteristics to understand the spatial charge distribution, absorber doping profile, and junction built-in potential. The frequency-dependent admittance was studied using simulated C-f characteristics to give an insight into the defect and the conductance. The Cesium tin (IV) halide (Cs 2 SnI 6) based device optimized with CuBi 2 O 4 , Cu 2 O, CuAlO 2 , and NiO HTLs has shown PCE of 28.18 %, 29.72 %, 29.43 %, and 29.33 %, respectively. [ABSTRACT FROM AUTHOR]

We have introduced a novel approach to enhance the perovskite solar cell efficiency by controlling the grain growth and light harvesting properties of perovskite crystallites. Instead of using a mesoporous TiO 2 layer, we have modified the surface microstructuring of the TiO 2 film by dispensing nano assembled TiO 2 submicron structures (nanobeads, NBs) on TiO 2 compact layer. With this new approach solar cell efficiency was improved significantly through an increase in both J sc and V oc . This high efficiency is attributed to crystallite size of the perovskite phase. These also act as light scattering centers giving higher current density and reduced recombination effects giving higher open circuit voltage. [ABSTRACT FROM AUTHOR]

Self-assembled monolayers (SAMs) are becoming widely utilized as hole-selective layers in high-performance p-i-n architecture perovskite solar cells. Ultrasonic spray coating and airbrush coating are demonstrated here as effective methods to deposit MeO-2PACz; a carbazole-based SAM. Potential dewetting of hybrid perovskite precursor solutions from this layer is overcome using optimized solvent rinsing protocols. The use of air-knife gas-quenching is then explored to rapidly remove the volatile solvent from an MAPbI3 precursor film spray-coated onto an MeO-2PACz SAM, allowing fabrication of p-i-n devices with power conversion efficiencies in excess of 20%, with all other layers thermally evaporated. This combination of deposition techniques is consistent with a rapid, roll-to-roll manufacturing process for the fabrication of large-area solar cells. [ABSTRACT FROM AUTHOR]

Traditional single-junction binary organic solar cells suffer from narrow absorption windows, limiting their ability to harvest photons. One promising approach to avoid this issue is through the construction of a ternary system to enhance the spectral response and efficiency. However, the complex morphology and photophysical processes within ternary blends leave the criteria of an effective third component unclear, and so they remain a challenge. In this work, we report on the fabrication of PTB7-Th:COi8DFIC-based ternary solar cells with enhanced efficiency by employing either a polymer donor or a nonfullerene acceptor as the third component. We demonstrate that the third component is highly associated with the condensed state of the host acceptor and is the primary factor in determining efficiency improvement. The π-π stacking molecular packing of COi8DFIC helps to maintain the optimal phase separation within the ternary blends and improves both the hole and electron charge mobilities, resulting in enhanced power conversion efficiency of over 14%, compared to 13.1% in binary devices. We also found an excessive amount of polymer donor or nonfullerene acceptor increases the phase separation and encourages lamellar crystallization with the host acceptor domain, resulting in reduced light-harvesting and external quantum efficiencies at long wavelengths. Our results provide a rational guide to selecting the third component to fabricate high-performance nonfullerene-based ternary solar cells. [ABSTRACT FROM AUTHOR]

The δ → α phase transformation is a crucial step in the solution-growth process of formamidinium-based lead triiodide (FAPbI3) hybrid organic-inorganic perovskite (HOIP) thin films for perovskite solar cells (PSCs). Because the addition of cesium (Cs) stabilizes the α phase of FAPbI3-based HOIPs, here our research focuses on FAPbI3(Cs) thin films. We show that having a large grain size in the δ-FAPbI3(Cs) non-perovskite intermediate films is essential for the growth of high-quality α-FAPbI3(Cs) HOIP thin films. Here grain coarsening and phase transformation occur simultaneously during the thermal annealing step. A large starting grain size in the δ-FAPbI3(Cs) thin films suppresses grain coarsening, precluding the formation of voids at the final α-FAPbI3(Cs)-substrate interfaces. PSCs based on the interface void-free α-FAPbI3(Cs) HOIP thin films are much more efficient and stable in the ambient atmosphere. This interesting finding inspired us to develop a simple room-temperature aging method for preparing coarse-grained δ-FAPbI3(Cs) intermediate films, which are subsequently converted to coarse-grained, high-quality α-FAPbI3(Cs) HOIP thin films. This study highlights the importance of microstructure meditation in the processing of formamidinium-based PSCs. [ABSTRACT FROM AUTHOR]

Mixed cation perovskites currently achieve very promising efficiency and operational stability when used as the active semiconductor in thin‐film photovoltaic devices. However, an in‐depth understanding of the structural and photophysical properties that drive this enhanced performance is still lacking. Here the prototypical mixed‐cation mixed‐halide perovskite (FAPbI3)0.85(MAPbBr3)0.15 is explored, and temperature‐dependent X‐ray diffraction measurements that are correlated with steady state and time‐resolved photoluminescence data are presented. The measurements indicate that this material adopts a pseudocubic perovskite α phase at room temperature, with a transition to a pseudotetragonal β phase occurring at ≈260 K. It is found that the temperature dependence of the radiative recombination rates correlates with temperature‐dependent changes in the structural configuration, and observed phase transitions also mark changes in the gradient of the optical bandgap. The work illustrates that temperature‐dependent changes in the perovskite crystal structure alter the charge carrier recombination processes and photoluminescence properties within such hybrid organic–inorganic materials. The findings have significant implications for photovoltaic performance at different operating temperatures, as well as providing new insight on the effect of alloying cations and halides on the phase behavior of hybrid perovskite materials. [ABSTRACT FROM AUTHOR]