Average Power Conversion Efficiency Research Articles

Compelling temperature behaviour of carbon-perovskite solar cell for fenestration at various climates

Sustainable building with smart windows is a promising technology. Due to their nanostructured and composite materials, perovskite devices can play a crucial role as tunable transparent or semi-transparent photovoltaics managing the buildings' energy health for harvesting, storage and utilization. Here, the temperature profile of different properties essential for the application of carbon perovskite solar cell (c-PSC) in the BIPV (building-integrated photovoltaics) field is illuminated cautiously to find out its feasibility at various climatic conditions. The results dictate small changes in transparency and efficiency with temperature, which also impacts other BIPV-related parameters. At temperatures 15 to 55°C, the AVT (average visible transmittance) remains at ∼27.5%, with an average power conversion efficiency (PCE) of ∼10%, whereas AVT slightly increases above 55°C in ambient conditions. Interestingly the PCE values greatly correlate with the AVT. The observed pseudo-thermochromic nature of c-PSC is explained by correlating transmittance with temperature coefficient and efficiency coefficient of transparency. The indispensable parameters like colour rendering index (CRI), correlated colour temperature (CCT), solar factor (SF) are calculated utilizing theoretical models at different temperatures to illuminate the colour comfort of these c-PSCs for BIPV integration. Even after temperature treatment, the CCT values >4800, and CRI values >80 signify the possibility of perovskites in different climates. Finally, glare daylight control is analyzed based on temperature and climate, taking an average over the summer and the winter of different places, which display both the advantages and disadvantages of c-PSCs. All the results from this case study suggest that c-PSC can become an integral part of fenestration at different KÖppen climates with suitable modifications.

Importance of tin (II) acetate additives in sequential deposited fabrication of Sn-Pb-based perovskite solar cells

Sn-Pb-based perovskite is a promising solar cell material for its low toxicity and narrow band gap. However, the poor crystallinity of Sn-containing perovskite films and the facile oxidation of Sn2+ are obstacles to the efficiency and stability of Sn-Pb-based perovskite solar cells (PSCs). Herein, we developed a new additive strategy of tin acetate (SnAc2) to fabricate high-quality (HC(NH2)2)n(CH3NH3)1-nPb0.7Sn0.3IxBr3-x films by a two-step method and simultaneously restrict the oxidation of Sn2+ to Sn4+ by coordination between Sn2+ and Ac-. Moreover, SnAc2 built an Sn-rich environment to alleviate the intrinsic Sn2+ vacancies. All these effectively reduced the defect state densities and carrier nonradiative recombinations in the device, resulting in improvements in the performance of PSCs. The PSCs with the SnAc2 additive exhibited a increase in average power conversion efficiency (PCE) from 15.60% to 16.69%. Furthermore, the phenethylammoniumiodide (PEAI) post-treatment was introduced to passivate the SnAc2-containing perovskite films. Finally, the optimal cell with a PCE of 17.93% was obtained, which was second-best compared to the reported Sn-Pb-based PSCs by the two-step methods. Furthermore, the producibility and stability of devices are also improved due to the inhibited oxidation of Sn2+ by SnAc2 additives and the protection of two-dimensional (2D) (PEA)2PbI4 perovskites, the unencapsulated PSC maintained 80.4% of its initial efficiency when stored in air after 24 days.

Enhanced proton irradiation resistance in Cs-doped CH3NH3PbI3 films and solar cells

Mixed-cation perovskite solar cells have attracted tremendous attention in space applications due to their excellent power conversion efficiency (PCE) and stability to light and heat. Although the evolution of photovoltaic performance in different space environments has been investigated, the role of inorganic cesium ions (Cs+) in the enhancement of irradiation resistance needs to be further clarified. Herein, the structure and performance evolution of Cs-doped CH3NH3PbI3 (MAPbI3) films and planar heterojunction devices under proton irradiation up to 1 × 1016 p cm−2 were studied. 5% of Cs+ doping can increase the cohesive energy of MAPbI3 and effectively alleviate the lattice strain induced by proton irradiation, thereby enhancing the crystallinity and stability of films. The bandgap changes of irradiated Cs0.05MA0.95PbI3 films under the identical fluence were only one third of that of MAPbI3 films. Upon irradiation under the fluence of 1 × 1014 p cm−2, the density of trap states in the undoped and 5%Cs-doped films increased by 71% and 9%, respectively, and the average PCE of 20 corresponding devices decreased only by 12% and 9%, respectively. This proves that the replacement of organic methylamine ion with inorganic cesium ion contributes to the improvement of MAPbI3 resistance to proton irradiation, thus confirming the application prospects of mixed-cation or all-inorganic perovskite solar cells in spacecraft.

High-performance Ruddlesden-Popper two-dimensional perovskite solar cells via solution processed inorganic charge transport layers.

Two-dimensional (2D) layered halide perovskites have been shown to enable improved long-term stability in comparison to the well-known three-dimensional hybrid organic-inorganic halide perovskites. The optoelectronic properties of the 2D perovskites are strongly influenced by the chemical nature of the charge transport layer. In this work, we fabricated Ruddlesden-Popper 2D perovskite solar cells (PSCs) using solution processed inorganic NiOx and a C60 : C70 (1 : 1) mixture as the hole and electron transport layers, which significantly improved the performance of the 2D PSCs. Time resolved photoluminescence measurements indicate the shortened lifetime of excitons, which demonstrates the excellent charge extraction properties. The PSCs based on these inorganic charge transport materials (CTMs) exhibit an average power conversion efficiency (PCE) of 14.1%, which is higher than that (12.3%) of PSCs using organic CTMs of poly(3,4-ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT:PSS) and phenyl-C61-butyric acid methyl ester (PCBM). Compared with PEDOT:PSS and PCBM based cases, the PSCs using inorganic CTMs also show improved long-term stability, with the PCE degradation significantly suppressed from 20% to 12% after a measurement of 15 days. The best PSCs using NiOx and C60 : C70 show a high PCE of 14.4%, with a stable power output and negligible hysteresis.

β-cyclodextrin–polyacryloyl hydrazide-based surface modification for efficient electron-collecting electrodes of indoor organic photovoltaics

Indoor organic photovoltaics (OPVs) show immense potential as a reliable energy harvester for powering emerging Internet of Things devices because of their unique optoelectrical properties. The extremely low number of charge carriers under indoor lighting conditions in comparison to 1-sun conditions necessitates different techniques to optimize the performance of indoor OPVs. In this study, an indium tin oxide (ITO) surface was modified using a water-soluble β-cyclodextrin–polyacryloyl hydrazide (CD–PAH). The abundant amine functional groups on the polyacryloyl hydrazide arms induce a vacuum-level shift owing to their excellent electron-withdrawing ability. Consequently, the work function (WF) of ITO decreased from 4.5 to 4.1 eV, providing a suitable energy-level alignment between ITO and the photoactive layer. The photovoltaic performance of inverted poly(3-hexylthiophene):indene-C60 bisadduct-based OPVs with the surface-treated ITO was evaluated under various lighting conditions. The average power conversion efficiency of the optimized OPV increased substantially from 1.2 ± 0.1% to 3.5 ± 0.1% under 1 sun illumination and 2.4 ± 0.2% to 8.1 ± 0.4% under light-emitting diode illumination. This remarkable performance improvement can be attributed to the excellent transmittance, smooth surface morphology, and suitable WF of the surface-modified ITO.

Starburst configured imidazole-arylamine organic sensitizers for DSSC applications

In this study, special consideration was given to the design and synthesis of imidazole-arylamine-based organic sensitizers with three arylamine donors (Carbazole, Triphenylamine and Phenothiazine) paired with cyanoacrylic acid acceptor to form D-D-A architecture. Phenothiazine-imidazole dye (PZIM) was found to be the best for DSSC applications in the D-D-A set. Hence, we further extended the conjugation of PZIM dye by three different spacers such as benzene (PZIMBe), thiophene (PZIMTh), and furan (PZIMFu) having different resonance energies, which resulted in the design of D-D-π-A. We have carried out the photo-physical, electrochemical, and photovoltaic performance for these six dyes. The PZIM, PZIMTh and PZIMFu dyes were identified as the efficient among the six with an average power conversion efficiency of 7.0%, 7.10% and 7.30%, respectively. Thiophene and furan outperformed benzene spacer as the best linkers in the D-D-π-A configuration. Grafting the bulky imidazole moiety onto the arylamine donor is considered to be a promising approach for tuning photovoltaic parameters by increasing the electron richness of the main electron donor core, increasing solubility, and suppressing aggregation.

Bridging Effects of Sulfur Anions at Titanium Oxide and Perovskite Interfaces on Interfacial Defect Passivation and Performance Enhancement of Perovskite Solar Cells

Interfacial defects at the electron transport layer (ETL) and perovskite (PVK) interface are critical to the power conversion efficiency (PCE) and stabilities of the perovskite solar cells (PSCs) via significantly affecting the quality of both interface contacts and PVK layers. Here, we demonstrate a simple ionic bond passivation method, employing Na2S solution treatment of the surface of titanium dioxide (TiO2) layers, to effectively passivate the traps at the TiO2/Cs0.05(MA0.15FA0.85)0.95Pb(Br0.15I0.85)3 PVK interface and enhance the performance of PSCs. X-ray photoelectron spectroscopy and other characterizations show that the Na2S treatment introduced S2– ions at the TiO2/PVK interface, where S2– ions effectively bridged the TiO2 ETL and the PVK layer via forming chemical bonds with Ti atoms and with uncoordinated Pb atoms and resulted in the reduced defect density and improved the crystallinity of PVK layers. In addition, the S2– ions can effectively enlarge the grain size of the PVK layers. The average PCE of solar cells is improved from 15.77 to 19.06% via employing the Na2S-treated TiO2 layers. This work demonstrates a simple and facile interface passivation method using ionic bond passivation to afford high-performance PSCs. The bridging effect of S2– ions may inspire the further exploration of the ionic bond passivation and sulfur-based passivation materials.

Surface dipole assisted charge carrier extraction in inverted architecture perovskite solar cells

Engineering the energetics of perovskite solar cells through the introduction of surface dipoles that assist with charge carrier extraction is a promising route to enhance the device performance without altering other device layers or fabrication parameters. In this work, we introduce four different derivatives of dicationic phosphonium-bridged ladder stilbenes (PYMC) in inverted perovskite solar cells with the device structure of ITO/Meo-2pacz/perovskite/PYMC/phenyl-C61-butyric acid methyl ester (PCBM)/bathocuproine/Ag. We show that the derivatives introduce a dipole at the perovskite/PCBM interface, which for derivatives with suitable energy levels can enhance the charge carrier extraction, leading to a quenched photoluminescence of perovskite thin films and an improved photovoltaic performance. As a result, both a higher average and maximum power conversion efficiency could be achieved and an overall better device reproducibility. This work highlights the significant potential of energetics engineering between perovskites and transport layers in perovskite solar cells for highly efficient photovoltaic devices.

Outdoor Characterization of a Plasmonic Luminescent Solar Concentrator

Plasmonic luminescent solar concentrators (PLSCs) have been shown to enhance the optical performance and power conversion efficiency of LSCs, due to added plasmonic gain in the medium. Despite the promising outlook of a PLSC through plasmonic coupling, device characterization and performance have not been verified in the real outdoor conditions, with varying direct and diffuse solar irradiation. In this work, characterization of a PLSC device of dimensions 4.5 \(\times\) 4.5 \(\times\) 0.3 cm3 embedded with Lumogen Red 305 dye and plasmonic gain medium of gold core silver shell nano cuboids was carried out in outdoor conditions of Dublin, Ireland. Optimized PLSC device power output at different solar insolation was compared to a reference photovoltaic (PV) cell and an optimized luminescent solar concentrator (LSC) device. The effect of the solar disc position, solar insolation, PV cell surface temperature, diurnal, and seasonal variation on the performance of the PLSC device is studied. The key observation was that PLSC average power conversion efficiency was 1.4 times more than the PV cell in cloudy and diffuse solar conditions. The PLSC device performed 45% better than a PV cell in December than July, as December has higher diffuse solar irradiation. Even though the PLSC device absorbs only 31% and transmits 69% incident solar irradiation in the concerned visible range of 380–750 nm. The preliminary outdoor characterization on a small-scale PLSC establishes its viability in a diffuse to direct solar radiation ratio throughout the year as well as establishing its benefits for integration in buildings.

Sub-nanometer atomic layer deposited Al2O3 barrier layer for improving stability of nonfullerene organic solar cells

Organic solar cells (OSCs) is a promising next-generation photovoltaic technology, however, the device stability remains to be the main barrier for its future commercialization. Herein, we reported the application of a sub-nanometer Al2O3 barrier layer in nonfullerene OSCs via atomic layer deposition (ALD), for the purpose of preventing metal ion diffusion from indium tin oxide (ITO) into the polymer layer caused by the corrosion of Poly(3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS). The thickness of the ALD-Al2O3 barrier layer was precisely optimized by controlling the number of ALD cycles (n) to achieve simultaneously good photoelectric properties and conformal coverage. An average power conversion efficiency (PCE) of 15.02% was demonstrated for the optimal OSCs with ALD-Al2O3 barrier layer. The above mentioned suppression of metal ion diffusion was experimentally confirmed by the cross sectional observations of transmission electron microscopy (TEM) and chemical mapping from energy-dispersive X-ray spectroscopy (EDX), resulting in a significantly improved operational stability with a device lifetime 3-times longer than that without ALD-Al2O3 barrier layer. Such ALD-assisted interface modification provides an effective approach to realize high-performance and stable OSCs.

Tin Oxide Modified Titanium Dioxide as Electron Transport Layer in Formamidinium-Rich Perovskite Solar Cells

The design of electron transport layers (ETLs) with good optoelectronic properties is one of the keys to the improvement of the power conversion efficiencies (PCEs) and stability of perovskite solar cells (PSCs). Titanium dioxide (TiO2), one of the most widely used ETL in PSCs, is characterized by low electrical conductivity that increases the series resistance of PSCs, thus limiting their PCEs. In this work, we incorporated tin oxide (SnO2) into titanium dioxide (TiO2) and studied the evolution of its microstructural and optoelectronic properties with SnO2 loading. The thin films were then integrated as ETLs in a regular planar Formamidinium (FA)-rich mixed lead halide PSCs so as to assess the overall effect of SnO2 incorporation on their charge transport and Photovoltaic (PV) characteristics. Analysis of the fabricated PSCs devices revealed that the best performing devices; based on the ETL modified with 0.2 proportion of SnO2; had an average PCE of 17.35 ± 1.39%, which was about 7.16% higher than those with pristine TiO2 as ETL. The improvement in the PCE of the PSC devices with 0.2 SnO2 content in the ETL was attributed to the improved electron extraction and transport ability as revealed by the Time Resolved Photoluminescence (TRPL) and Electrochemical Impedance Spectroscopy (EIS) studies.

Opportunities of copper addition in CH3NH3PbI3 perovskite and their photovoltaic performance evaluation

Perovskite solar cells (PSCs) have encountered a fulgurant development in their power-conversion efficiency (PCEs) generation in the drive to provide a facile, cheap and clean source of energy over just a few years. The most efficient PSCs are fabricated using CH3NH3PbI3 (MAPbI3) perovskite. However, being a promising photovoltaic (PV) performance piloted by MAPbI3, Pb-toxicity and poor stability obstructs the progress of PSCs in PV technology. In this regard, replacing Pb with some environmentally friendly, cheaper, and similar optoelectronic behaviour related alternative material or element is highly desirable. In this work, an attempt was made on copper as Cu (I) addition in the perovskite, MAPbI3 through some exotic ways in an intention of Pb replacement, i.e., complete Pb replacement with Cu, which generates MACuxI3 (1 ≤ x ≥ 2); partial lead replacement, i.e., MAPb1−xCuxI3; and cocktail perovskite, i.e., both MAPbI3 and MACuxI3 mixture, and finally they are employed for carbon-based perovskite solar cells. Remarkably, Cu incorporation facilitates the near-infrared (NIR) absorption, indicating a maximum solar spectrum absorbance. Integration of Cu as MAPb1−xCuxI3 results in the maximum PCE of ~12.85%, whereas using 1:1 cocktail perovskite solution of MAPbI3 and MACuxI3 exhibits an average PCE of ~12.43%. On the other hand, during complete Pb substituted perovskites, MACuxI3, the device has only experienced an average PCE of ~4.0%. However, MACuxI3-based PSCs lead to negligible PCE degradation as perceived up to 1000 h, whereas Pb-based other devices are experienced rapid PCE depletion over the same period. Noticeably, Cu-incorporation facilitates a comparatively steeper and lesser PCE degradation rate than Pb-based PSCs. These results may help exploit unlimited possibilities of the potential application of Pb-free based highly stable solar cells and highlights the opportunities for broad solar absorption towards the NIR route and enhanced device stability. Besides, Cu employment has the advantages of environmentally benign impact, earth abundance, good thermal and aqueous stability.

Polymer Hole Transport Materials for Perovskite Solar Cells via Buchwald–Hartwig Amination

The development of low-cost materials for charge-selective contacts that provide good energetic alignment with perovskite active layers, favorable thermal properties, and lead to efficient photoconversion is becoming an increasingly important aspect of the perovskite solar cell (PSC) field. Presented here is a series of polymers based on a one-pot polymerization of aryl dihalides with primary aryl amines to produce solution-processable polymers in high yield, with simple purification, and promising properties for high performing P-I-N PSC devices. How these properties can be tuned by careful selection of the reactant chemical moieties is discussed. Through this strategy, a wide range of relevant properties such as glass transition temperature, highest occupied molecular orbital tuning, and polydispersity are explored. When implemented into devices using a triple-cation FAMACs perovskite active layer, the hole transport material series shows average power conversion efficiencies (PCE) in excess of 17%, which is comparable to controls using state-of-the-art poly(triarylamine). How different synthetic parameters such as the reaction time and purification protocol impact device performance is also investigated.

High performance inverted perovskite solar cells using PEDOT:PSS/KCl hybrid hole transporting layer

PEDOT:PSS is one of the most widely used hole transporting layer for inverted perovskite solar cells. Yet the performances of the corresponding perovskite solar cells are not satisfactory. Here, we demonstrate that KCl modified PEDOT:PSS film can promote the crystallization of perovskite film and enlarge the perovskite crystals. At the same time, KCl can diffuse into the perovskite film and effectively passivate the defects. As a result, inverted perovskite solar cells fabricated on 10 mg mL −1 PEDOT:PSS/KCl films exhibit an average power conversion efficiency of 16.24 %, which is enhanced by 17.77 % compared with the reference perovskite solar cells. Open circuit voltage of 1.009 V and power conversion efficiency of 17.09 % have also been demonstrated using the optimized 10 mg mL −1 PEDOT:PSS/KCl films. • KCl is used to modify the PEDOT:PSS film. • Island and dendrite KCl structures are observed in the PEDOT:PSS/KCl films. • Charge carrier recombination is suppressed using the PEDOT:PSS/KCl films. • Champion power conversion efficiency of 17.09 % has been demonstrated.

“Coffee ring” controlment in spray prepared >19% efficiency Cs0.19FA0.81PbI2.5Br0.5 perovskite solar cells

Achieving high-quality perovskite films with uniform morphology and homogeneous crystallinity is challenging owing to the coffee ring effect (CRE) in the spray-coating technologies. In this study, an evaporation/spray-coating two-step deposition method is used to fabricate Cs0.19FA0.81PbI2.5Br0.5 light harvesters for perovskite solar cells (PSCs). Considering the solid–liquid reaction, we establish a reaction-dependent regulating strategy that inhibits CRE successfully and prepare a high-quality perovskite layer, wherein the solvent for the FAI/Br solution during the spraying process is changed from isopropanol to n-butyl alcohol (NBA). The retarded-drying-enhanced spreading of the NBA solution inhibits contact line pinning to suppress the capillary flows and increases the reaction between metal halides (CsI/PbI2) and organic salts (FAI/Br), which result in a reduction in the accumulation of solutes in the periphery effectively inhibiting CRE. Consequently, we obtain a high performance Cs0.19FA0.81PbI2.5Br0.5 PSC with a power conversion efficiency (PCE) of 19.17%. An enlarged perovskite film (10 × 10 cm2) containing 40 sub-cells is prepared. The average PCE of these devices is 18.33 ± 0.56%, proving the reliability of the “coffee ring” regulating strategy. This study provides an effective approach for CRE controlment in spraying technology to achieve high repeatability devices with good performance.

Inverted perovskite solar cells based on inorganic hole transport material of CuInS2 with high efficiency and stability

In this paper, CuInS2 nanocrystals were prepared and used to fabricate inverted perovskite solar cells (PSCs) with the CuInS2 nanocrystals as a hole transport material (HTM). The average power conversion efficiency (PCE) of the PSCs with CuInS2 is 16.22%, which is close to the average PCE of the NiO-based devices (17.32%). The PCE of the champion PSC with CuInS2 has been reached 17.34%, and that of the control PSC with NiO (18.33%). Moreover the inverted PSCs with CuInS2 present an enhanced stability compared with the NiO-based control devices. The PCE of the inverted PSCs based on CuInS2 maintains 70% of the original when they are placed in ambient atmosphere for 96 h, while the PCE of the control devices with NiO decreased to 60% of the beginning. These results indicate that CuInS2 nanocrystal is an excellent HTM which could be applied to assemble the inverted PSCs.

ITO/SnO2 Interface Defect Passivation via Atomic Layer Deposited Al2O3 for High‐Efficiency Perovskite Solar Cells

Indium tin oxide (ITO) substrate is widely used as a transparent electrode in perovskite solar cells (PSCs). However, the intrinsic defects, especially on the ITO surface, are one of the most key factors to restrict the power conversion efficiency (PCE) of PSCs. Herein, a facile method to passivate the defects of the ITO/SnO2 interface using an ultrathin aluminum oxide (Al2O3) layer through atomic layer deposition, of which the film thickness is exactly regulated, is first demonstrated. With the optimized film thickness, carrier recombination at the ITO/SnO2 interface is effectively suppressed within the three‐cycle Al2O3 layer, which results in an improved charge carrier collection efficiency from the SnO2 electron transporting layer to the ITO electrode. Furthermore, a thinner Al2O3 film (one cycle) does not passivate the interface defect effectively, and a thicker Al2O3 film (five cycles) retards the charge carrier extraction at the ITO/SnO2 interface. The average PCE of the three‐cycle Al2O3‐based PSC is 19.43%, among which the champion PCE is 20.24%, showing a significant improvement compared with the counterpart with an average PCE of 18.50%.

Intermediate Phase-Free Process for Methylammonium Lead Iodide Thin Film for High-Efficiency Perovskite Solar Cells.

Solvent engineering by Lewis‐base solvent and anti‐solvent is well known for forming uniform and stable perovskite thin films. The perovskite phase crystallizes from an intermediate Lewis‐adduct upon annealing‐induced crystallization. Herein, it is explored the effects of trimethyl phosphate (TMP), as a novel aprotic Lewis‐base solvent with a low donor number for the perovskite film formation and photovoltaic characteristics of perovskite solar cells (PSCs). As compared to dimethylsulfoxide (DMSO) or dimethylformamide (DMF), the usage of TMP directly crystallizes the perovskite phase, i.e., reduces the intermediate phase to a negligible degree, right after the spin‐coating, owing to the high miscibility of TMP with the anti‐solvent and weak bonding in the Lewis adduct. Interestingly, the PSCs based on methylammonium lead iodide (MAPbI3) derived from TMP/DMF‐mixed solvent exhibit a higher average power conversion efficiency of 19.68% (the best: 20.02%) with a smaller hysteresis in the current‐voltage curve, compared to the PSCs that are fabricated using DMSO/DMF‐mixed (19.14%) or DMF‐only (18.55%) solvents. The superior photovoltaic properties are attributed to the lower defect density of the TMP/DMF‐derived perovskite film. The results indicate that a high‐performance PSC can be achieved by combining a weak Lewis base with a well‐established solvent engineering process.

Improving the Morphology Stability of Spiro-OMeTAD Films for Enhanced Thermal Stability of Perovskite Solar Cells.

To guarantee a long lifetime of perovskite-based photovoltaics, the selected materials need to survive relatively high-temperature stress during the solar cell operation. Highly efficient n-i-p perovskite solar cells (PSCs) often degrade at high operational temperatures due to morphological instability of the hole transport material 2,2',7,7'-tetrakis (N,N-di-p-methoxyphenyl-amine)9,9'-spirobifluorene (Spiro-OMeTAD). We discovered that the detrimental large-domain spiro-OMeTAD crystallization is caused by the simultaneous presence of tert-butylpyridine (tBP) additive and gold (Au) as a capping layer. Based on this discovery and our understanding, we demonstrated facile strategies that successfully stabilize the amorphous phase of spiro-OMeTAD film. As a result, the thermal stability of n-i-p PSCs is largely improved. After the spiro-OMeTAD films in the PSCs were stressed for 1032 h at 85 °C in the dark in nitrogen environment, reference PSCs retained only 22% of their initial average power conversion efficiency (PCE), while the best target PSCs retained 85% relative average PCE. Our work suggests facile ways to realize efficient and thermally stable spiro-OMeTAD containing n-i-p PSCs.

Improvement of interfacial contact for efficient PCBM/MAPbI3 planar heterojunction solar cells with a binary antisolvent mixture treatment

Atomic-force microscopic images, x-ray diffraction patterns, Urbach energies and photoluminescence quenching experiments show that the interfacial contact quality between the hydrophobic [6,6]-phenyl-C61-buttric acid methyl ester (PCBM) thin film and hydrophilic CH3NH3PbI3 (MAPbI3) thin film can be effectively improved by using a binary antisolvent mixture (toluene:dichloromethane or chlorobenzene:dichloromethane) in the anti-solvent mixture-mediated nucleation process, which increases the averaged power conversion efficiency of the resultant PEDOT:PSS (P3CT-Na) thin film based MAPbI3 solar cells from 13.18% (18.52%) to 13.80% (19.55%). Beside, the use of 10% dichloromethane (DCM) in the binary antisolvent mixture results in a nano-textured MAPbI3 thin film with multicrystalline micrometer-sized grains and thereby increasing the short-circuit current density and fill factor (FF) of the resultant solar cells. It is noted that a remarkable FF of 80.33% is achieved, which can be used to explain the stable photovoltaic performance without additional encapsulations.