Printable Mesoscopic Perovskite Solar Cells Research Articles

Selective coordination of polyazin sapanisertib with halide vacancy for printable mesoscopic perovskite solar cells

The mitigation of under-coordinated Pb2+ (halide vacancy) defect remains an imperative challenge in the perovskite solar cells, especially printable mesoscopic perovskite solar cells (FP-PSCs). Here we report a commercial-available polyazin anticancer drug Sapanisertib as coordination passivator of halide vacancies in FP-PSCs, thereby achieving the photoelectric conversion efficiency (PCE) to 18.46%, along with a record certified PCE of 18.27%. In polazin Sapanisertib (Sap), there exists two kinds of nitrogen atoms: in-aromatic ring (in purine and oxazole rings, IAR-Ns) and out-aromatic ring (substituted amino groups, OAR-Ns). Through multiple characterizations, and DFT calculations show that substituted amino groups OAR-Ns hardly get interaction with the halide vacancy due to the distribution of charge density in Sapanisertib. Our work suggests that the selective coordination is of great significance for the design of high-performance passivators for printable mesoscopic perovskite solar cells.

Enhancing the Performance of Fa‐Based Printable Mesoscopic Perovskite Solar Cells via the Polymer Additive

AbstractThe low cost and scalability advantages of printable mesoscopic perovskite solar cells (p‐MPSCs) are impaired by the issue of limited power conversion efficiency (PCE). Herein, the PCE of p‐MPSCs is improved by introducing the polymer additive polyacrylonitrile (PAN) into the formamidinium (FA)‐based perovskite for crystallization and defect modulation. PAN forms hydrogen bond and coordination bond with halide perovskite through its C≡N group. Such interactions improve the crystallization and filling of FA‐based perovskite in the mesoscopic scaffold and bring a long carrier lifetime by passivating defects. The synergy improves the PCE of p‐MPSCs from 16.80% to 18.33%. Meanwhile, the hydrophobic nature of PAN enhances the device's resistance against moisture. This work demonstrates that the polymer additive is a promising choice for breaking the PCE limit of p‐MPSCs.

A Polymer Defect Passivator for Efficient Hole‐Conductor‐Free Printable Mesoscopic Perovskite Solar Cells

AbstractDue to the low cost and excellent potential for mass production, printable mesoscopic perovskite solar cells (p‐MPSCs) have drawn a lot of attention among other device structures. However, the low open‐circuit voltage (VOC) of such devices restricts their power conversion efficiency (PCE). This limitation is brought by the high defect density at perovskite grain boundaries in the mesoporous scaffold, which results in severe nonradiative recombination and is detrimental to the VOC. To improve the perovskite crystallization process, passivate the perovskite defects, and enhance the PCE, additive engineering is an effective way. Herein, a polymeric Lewis base polysuccinimide (PSI) is added to the perovskite precursor solution as an additive. It improves the perovskite crystallinity and its carbonyl groups strongly coordinate with Pb2+, which can effectively passivate defects. Additionally, compared with its monomer, succinimide (SI), PSI serves as a better defect passivator because the long‐chained macromolecule can be firmly anchored on those defect sites and form a stronger interaction with perovskite grains. As a result, the champion device has a PCE of 18.84%, and the VOC rises from 973 to 1030 mV. This study offers a new strategy for fabricating efficient p‐MPSCs.

Two Birds with One Stone: Defect Passivation and Energy Level Optimization Achieved by Using Ionic Liquid Additives for Printable Mesoscopic Perovskite Solar Cells with Efficiency beyond 16%

Two Birds with One Stone: Defect Passivation and Energy Level Optimization Achieved by Using Ionic Liquid Additives for Printable Mesoscopic Perovskite Solar Cells with Efficiency beyond 16%

Depth-Dependent Post-Treatment for Reducing Voltage Loss in Printable Mesoscopic Perovskite Solar Cells.

The printable mesoscopic perovskite solar cells consisting of a double layer of metal oxides covered by a porous carbon film have attracted attention due to their industrialization advantages. However, the tens-of-micrometer thickness of the triple scaffold leads to a challenge for perovskite to crystallize and for the charge carriers to separate and travel to the electrode, which limits the open circuit voltage (VOC ) of such devices. In this work, a depth-dependent post-treatment strategy is demonstrated to synergistically passivate defects and tune interfacial energy band alignment. Two thiophene derivatives, namely 3-chlorothiophene (3-CT) and 3-thiophene ethylenediamine (3-TEA), are selected for the post-treatment. Energy-dispersive X-ray spectroscopy proves that 3-CT is uniformly distributed throughout the triple scaffold and effectively passivates the defects of the bulky perovskite, while 3-TEA reacts rapidly with the loose perovskite in the carbon layer to form 2D perovskite, forming a type II energy band alignment at the perovskite/carbon interface. As a result, the defect-assisted recombination is suppressed and the interfacial energy band is regulated, increasing the VOC to 1012mV. The PCE of the devices is enhanced from 16.26% to 18.49%. This depth-dependent post-treatment strategy takes advantage of the unique structure and provides a new insight for reducing the voltage loss.

Comprehensively Improved the Performance of Carbon‐Based Printed Mesoscopic (FA)CsRbPbI3 Solar Cells by 3‐Pyridine Formamide

Excellent stability, low costs, and printability are the most significant features of printable mesoscopic perovskite solar cells (p‐MPSCs). However, the introduction of carbon electrodes reduces the cost of production while causing severe voltage losses within the p‐MPSCs. Herein, formamidine (FA), cesium, and rubidium are selected as A‐site cations (or cationic groups) in perovskite films, and nicotinamide (3‐pyridine formamide, NTM) is introduced as an additive to modify the perovskite films for the preparation of p‐MPSCs. The introduction of NTM can effectively passivate the crystal defects of perovskite films filled in the triple mesopores (mesoscopic TiO2/ZrO2/C), which enhances the pore filling and improves the carrier transportation and extraction efficiency. In addition, the amide group can effectively enhance the work function of the perovskite films and further increase the open‐circuit voltage (VOC) of the p‐MPSCs. Consequently, major benefitting from the significant increase in VOC (from 880 to 970 mV), the power conversion efficiency (PCE) of the NTM‐modified p‐MPSCs is improved up to 16.36%, which is nearly 20% improvement compared with the 14.36% of the control devices. In addition, the unencapsulated modified NTM‐modified (FA)CsRbPbI3 p‐MPSCs show excellent stability in air by maintaining 85% of the initial PCE after 90 days of storage.

Defect Passivation by a Sulfur‐Containing Lewis Base for Efficient Printable Mesoscopic Perovskite Solar Cells

In the rapid development of perovskite solar cells (PSCs), additive engineering has played a significant role for perovskite crystallization and passivation. The high density of defects at perovskite grain boundaries in the mesoporous scaffold leads to severe nonradiative recombination, which results in severe voltage loss. Herein, a sulfur‐containing Lewis base 2‐(methylthio)ethylamine hydrochloride (MTEACl) is applied in the perovskite precursor solution for printable mesoscopic PSCs with triple‐mesoscopic layer structure. Due to the strong electron donating ability of sulfur, the MTEACl can strongly interact with Pb2+, which can effectively passivate the defects of the perovskite. Correspondingly, the trap density of the perovskite is reduced, contributing to the improvement of power conversion efficiency from 15.18% to 17.17% and open circuit voltage to 995 mV.

Varied performance of printable mesoscopic perovskite solar cells by the non-stoichiometric precursor

Halide perovskite semiconductors such as MAPbI3 always fluctuate around their stoichiometric compositions due to the weighing or annealing, which causes performance variation of related devices. Here, we investigate the comprehensive impact of non-stoichiometric MAPbI3 precursor on the performance including power conversion efficiency (PCE), hysteresis, and stability of printable mesoscopic perovskite solar cells (p-MPSCs). Excess MAI improves PCE, suppresses hysteresis, and enhances stability by promoting hole transport and passivating defects evaluated by a designed mesoporous space-charge-limited-current device, while excess PbI2 impairs device performance. Replacing excess MAI with other monovalent cation halide salts including guanidinium iodide (GUAI), 2-phenylethylamine hydroiodide (PEAI) and rubidium iodide (RbI) further improves the device PCE to 17.02% and minimizes the hysteresis. Our work reveals that making monovalent cation halide salts such as MAI rather than PbI2 excessive is positive for the comprehensive performance enhancement of PSCs and developing more suitable salt substitution will benefit industrializing PSCs.

Semitransparent Printable Mesoscopic Perovskite Solar Cells for Tandem Solar Cells

The boosting efficiency of perovskite solar cells (PSCs) has evoked the interest in applying them in tandem structures, especially perovskite/silicon tandem solar cells. However, the tandem solar cells still face concerns about stability, upscaling, and cost‐effectiveness on the path to commercialization. Herein, an innovative tandem architecture based on the printable mesoscopic perovskite solar cells is proposed. By investigating the effects of indium tin oxide (ITO) particle size, annealing temperature, and dispersant on the performance of ITO mesoporous films, screen‐printable mesoscopic ITO electrode with an electron mobility of 7.5 cm2 V−1 s−1 and an average visible transmittance of over 80% is successfully obtained. The screen‐printed mesoporous titania, zirconia, and ITO are used as a scaffold and a semitransparent PSC with a champion power conversion efficiency of 9.38% is fabricated infiltrated with perovskites. Further, a perovskite/silicon tandem device which can remain stable for >720 h is demonstrated, highlighting the potential of screen‐printed inorganic scaffold structure in tandem photovoltaic technique.

Reducing Optical Reflection Loss for Perovskite Solar Cells Via Printable Mesoporous SiO2 Antireflection Coatings

AbstractThe power conversion efficiency (PCE) of single‐junction perovskite solar cells (PSCs) is being rapidly promoted towards their theoretical limit, with a certified value of 25.7%. Reducing optical loss will further contribute to PCE improvement. Here, the optical loss including reflection loss, absorption loss, and transmission loss in printable mesoscopic perovskite solar cells (p‐MPSCs) is analyzed. A printable mesoporous SiO2 antireflection coating for improving the transmittance of the fluorine‐doped tin oxide (FTO) glass substrate by reducing optical reflection at the air/glass interface is reported. With modulated porosity and thickness, the mesoporous SiO2 film constructs a graded refractive index interface and increases the transmittance of FTO glass by ≈2%–4% in the spectral range of 350–800 nm at normal incident angle with the highest transmittance improved from 85% to 89%. The SiO2 coating also exhibits wide‐angle and broadband antireflection properties. The coatings successfully help p‐MPSCs obtain about an average 3% enhancement in the short‐circuit current density (JSC) and PCE. This study demonstrates the necessity of optical management for efficient solar cells and provides a cost‐effective and scalable antireflection coating for the future realistic application of PSCs.

Surface Lattice Perturbation of Electron Transport Layer Reducing Oxygen Vacancies for Positive Photovoltaic Effect

For carbon‐based fully printable mesoscopic perovskite solar cells (FP‐PSCs), due to the serious interfacial defects formed in the uncontrollable crystallization process, modifying the interface between perovskite and electron transport layer is an effective way to enhance their photovoltaic performance. Herein, ultrathin ZrO2 is deposited on the mesoporous TiO2 surface by using spray pyrolysis, and Zr4+ intercalates into the TiO2 surface lattice and works together with Ti4+ and O2− ions. Thanks to this surface lattice perturbation of Zr4+, the reduction of surface oxygen vacancies of TiO2 (electron transport layer) decreases the density of defective states at the TiO2–perovskite interface inhibiting the Shockley–Read–Hall recombination (nonradiative recombination) in the charge cross‐interface transfer. Furthermore, both the open‐circuit voltage and short‐circuit current density are improved significantly. Based on perovskite Cs0.05(FA0.92MA0.08)0.95Pb(I0.92Br0.08)3 for carbon‐based FP‐PSCs, a high power conversion efficiency of 17.81% is obtained. It provides a novel idea and technology for efficient interfacial modification of the electron transport layer for FP‐PSCs.

Trivalent Europium Ions Doped CsPbBr3 for Highly Efficient and Stable Printable Mesoscopic Perovskite Solar Cells and Driving Water Electrolysis

The all‐inorganic CsPbBr3 perovskite exhibits the possibility of overcoming the substantial nonideal thermal, humidity, and photostability of hybrid organic–inorganic perovskite solar cells (PSCs) in photoelectronic devices. Specifically, the rapid development of CsPbBr3 perovskite has delivered device efficiencies >10%. However, the mismatched energy band alignment and bad crystallization quality are still potential obstacles for the superior performance of PSCs. Herein, by employing n‐type doping, trivalent europium cation is successfully introduced into the CsPbBr3 lattice. The better energy‐level alignment leads to further reduction of voltage losses. Besides, the large and uniform grains resulting from the improvement of crystallization after doping decrease the grain boundaries and reduce the nonradiative recombination center. The quality of the film improves substantially, which significantly enhances the photoabsorption and the short‐circuit current density. The efficiency of the carbon‐based printable mesoscopic PSCs is improved from 7.5% to 8.06% with 3 mol% Eu3+ doping, resulting in high open‐circuit voltage of 1.41 V. Based on the device with effective area of 1 cm2 and 60.075 cm2, the record power conversion efficiency of 5.41% and 1.14% is obtained. The device also displays excellent stability with driving water electrolysis.

A multifunctional piperidine-based modulator for printable mesoscopic perovskite solar cells

Printable mesoscopic perovskite solar cells (PSCs) have received extensive attention due to their convenient large-area fabrication and good stability. The further improvement of the power conversion efficiency (PCE) of such simplified PSC configuration is limited by the low open circuit voltage (VOC). The high density of defects at grain boundaries of perovskites inside the mesoporous scaffold can cause severe nonradiative recombination, which have negative effects on VOC. Additive engineering has demonstrated advantages in improving the perovskite crystallization inside the pores, passivating the defects of perovskite and enhancing the performance of printable mesoscopic PSCs. Herein, we introduce a multifunctional modulator 1-(2-Chloroethyl) piperidine hydrochloride (ClEP) as an additive into the perovskite precursor solution. Benefiting from the strong interaction between ClEP and perovskite, it can interact with non-coordinating ions and defect states to achieve multi-defect passivation. As a result, the VOC of the printable mesoscopic PSC increases from 895.25 mV to 982.24 mV and the ClEP-treated printable mesoscopic PSC reaches a champion PCE of 17.08%. This work provides a new approach for developing efficient printable mesoscopic PSCs.

Tautomeric Dual‐Site Passivation for Carbon‐Based Printable Mesoscopic Perovskite Solar Cells

AbstractAlthough ionic conjugated passivation systems, such as ionic liquids (ILs), have been used to passivate perovskite in carbon‐based printable mesoscopic perovskite solar cells (FP‐PSCs), their tautomerism process and synergistic effect of multifunctional groups have not yet caused enough attention. In this work, a series of novel ILs including 1‐allyl‐3‐methylimidazole tetrafluoroborate ([AMIm]BF4) and 1‐benzyl‐3‐methylimidazole tetrafluoroborate ([BzMIm]BF4) used as passivants for FP‐PSCs are reported. Combining Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculation, it is found that one of its tautomers (positive ion at the near end N atom of conjugated side chain) plays a key role on dual‐site simultaneous passivation. As the conjugation degree of side chain increases from allyl to benzyl, it not only effectively inhibits the non‐radiative charge recombination, but also reduces the passivation adsorption energy and increases the charge transfer rate. A high efficiency of 16.87% has been achieved with a high FF (>0.7), a Jsc of 23.88 mA cm–2 value and Voc value up to 1.0 V, by using the “tautomeric dual‐site passivation” strategy.

Highly Orientational Order Perovskite Induced by In situ-generated 1D Perovskitoid for Efficient and Stable Printable Photovoltaics.

Employing low-dimensional perovskite has been proven to be a promising approach to enhance the efficiency and stability of perovskite solar cells. Here, thiopheniformamidine hydrochloride is introduced into CH3 NH3 PbI3 -based printable mesoscopic perovskite solar cells, to form 1D iodide lead thiophenamidine (TFPbI3 ) in situ. This judiciously designed low-dimensional perovskite can effectively passivate the defect of perovskite and induce the perovskite crystals to grow in a direction perpendicular to the substrate. Thus, the obtained 1D@3D perovskite could suppress the charge recombination and promote the charge transfer significantly. Benefiting from its dual effect and robustness, a significantly improved power conversion efficiency of 17.42% is yielded. The authors also develop high-performance printable mesoscopic perovskite solar cells with a champion efficiency approaching 13% for aperture area about 11.8 cm2 , as well as outstanding operational stability, retaining 90% of the original power conversion efficiency after 1000 hours of continuous illumination at the maximum power point in air.

Minimizing the Voltage Loss in Hole‐Conductor‐Free Printable Mesoscopic Perovskite Solar Cells

AbstractThe hole‐conductor‐free printable mesoscopic perovskite solar cells based on the inorganic scaffolds of mesoporous titania, mesoporous zirconia, and porous carbon have attracted much attention due to their excellent stability and low manufacturing cost. However, in such hole‐conductor‐free devices, the transport of the photogenerated holes is dominated by the diffusion‐assisted charge carrier movement, while the driving force is insufficient. Reinforcing the built‐in electric field (BEF) is an effective strategy to promote oriented carrier transport. Herein, by using an optimized two‐step deposition method, the BEF is reinforced by creating a work function difference of perovskite (Δµ) in different layers via a gradient self‐doping. The enhanced BEF improves the hole transport and extraction, and significantly reduces the carrier recombination losses in the device. As a result, an average open‐circuit voltage improvement over 60 mV and a power conversion efficiency of 17.68% are achieved without any additives or complex processes. This strategy provides a new approach toward fabricating highly efficient printable mesoscopic perovskite solar cells with reduced carrier recombination losses.

Highly oriented MAPbI3 crystals for efficient hole-conductor-free printable mesoscopic perovskite solar cells

Highly crystalline perovskite films with large grains and few grain boundaries are conducive for efficient and stable perovskite solar cells. Current methods for preparing perovskite films are mostly based on a fast crystallization process, with rapid nucleation and insufficient growth. In this study, MAPbI3 perovskite with inhibited nucleation and promoted growth in the TiO2/ZrO2/carbon triple mesoscopic scaffold was crystallized by modulating the precursor and the crystallization process. N-methylformamide showed high solubility for both methylammonium iodide and PbI2 and hampered the formation of large colloids in the MAPbI3 precursor solution. Furthermore, methylammonium chloride was added to reduce large colloids, which are a possible source of nucleation sites. During the crystallization of MAPbI3, the solvent was removed at a slow controlled speed, to avoid rapid nucleation and provide sufficient time for crystal growth. As a result, highly oriented MAPbI3 crystals with suppressed non-radiative recombination and promoted charge transport were obtained in the triple mesoscopic layer with disordered pores. The corresponding hole-conductor-free, printable mesoscopic perovskite solar cells exhibited a highest power conversion efficiency of 18.82%. The device also exhibited promising long-term operational stability of 1000 h under continuous illumination at maximum power point at 55 ± 5 °C and damp-heat stability of 1340 h aging at 85 °C as well as 85% relative humidity.

Cellulose‐Based Oxygen‐Rich Activated Carbon for Printable Mesoscopic Perovskite Solar Cells

Carbon electrodes (CEs) are demonstrated as the most stable and cost‐effective back electrodes for perovskite solar cells (PSCs), which influence the performance of related PSCs significantly. Herein, oxygen‐rich activated carbon (AC) is synthesized from the most abundant biomass resource, cellulose, via a feasible carbonization and oxidization process and applied in CEs for hole‐conductor‐free printable mesoscopic PSCs (p‐MPSCs). The obtained cellulose‐based activated carbon (CAC) exhibits a high specific area of 477.14 m2 g−1 and possesses a high oxygen content of 11.9%, promoting the wettability and contact between CEs and perovskites. Moreover, the high oxygen content also leads to an elevated work function of CEs. As a result, p‐MPSCs filled with (5‐AVA)0.03(MA)0.97PbI3 based on CEs containing CAC give an efficiency of 15.5%, whereas those devices based on CEs with no CAC give an efficiency of 13.8%. The improved efficiency benefits from the promoted fill factor and open circuit voltage due to the optimized energy level alignment and enhanced charge extraction by CAC. This work presents a good example for the value‐added utilization of cellulose in the energy conversion systems and offers a feasible strategy for preparing oxygen‐rich CE for PSCs with enhanced performance.

Enhanced perovskite electronic properties via A-site cation engineering

Organic-inorganic halide perovskites have emerged as excellent candidates for low-cost photovoltaics and optoelectronics. While the predominant recent trend in designing perovskites for efficient and stable solar cells has been to mix different A-site cations, the role of A-site cations is still limited to tune the lattice and bandgap of perovskites. Herein we compare the optoelectronic properties of acetamidinum (Ace) and guanidinium (Gua) mixed methylammonium lead iodide perovskites and shed a light on the hidden role of A-site cation on the carrier mobility of mixed-cation lead iodide perovskites. The cations do not affect the bandgap of the perovskites since the orbitals from Ace and Gua do not contribute to the band edges of the material. However, the mobility of the Ace mixed perovskite is significantly enhanced to be an order of magnitude higher than that of the pristine perovskite. We apply the Ace mixed perovskite in hole-conductor-free printable mesoscopic perovskite solar cells and obtain a stabilized PCE of over 18% (certified 17.7%), which is the highest certified efficiency so far.

Effect of polystyrene treatment on the efficiency and stability of fully printable mesoscopic perovskite solar cells with carbon electrode

Hole conductor-free, fully printable mesoscopic perovskite solar cells with carbon electrode (PM-PSCs) have a good commercialization prospect because of low-cost production and high power conversion efficiency (PCE). Currently, the problem of improving the stability of perovskite solar cells (PSCs) is very important for commercialization. Interfacial engineering using polymers is an effective method to improve the efficiency and stability of PSCs. We prepared PM-PSCs by treatment with the toluene solution containing polystyrene (PS) on the carbon electrode of the PM-PSCs, which would improve the charge transfer and greatly suppressed charge recombination in PS treated PM-PSCs, and also could greatly prevent degradation of perovskite into PbI2. The PS treated PM-PSCs showed higher stability to light and moisture than the control, and the PCE was improved from 11.31% (control) to 14.03%.