All-inorganic Perovskite Solar Cells Research Articles

Double-Side healing at CsPbI2Br/ZnO interface by bipyrimidine hydroiodide enables inverted solar cells with enhanced efficiency and stability

Inorganic perovskite solar cells (PSCs) with inverted (p-i-n) configuration are important for the development of tandem solar cells. Nevertheless, inverted all-inorganic PSCs still remain challenging due to the high-density defects in the perovskite and inorganic charge-transporting layer. Herein, we demonstrate a double-side healing strategy to simultaneously improve the performance of perovskite and electron transporting layer (ETL). Specifically, bipyrimidine hydroiodide (BP-HI) is introduced at the CsPbI2Br/ZnO interface in inverted PSC. A combined microscopic, mass spectrometric and spectroscopic study reveals that the BP-HI could diffuse into not only perovskite grain boundaries (GBs) but also the ZnO layer. This double-side healing leads to improved conduction through perovskite grain, suppressed ion-migration along perovskite GBs, enhanced built-in electric field cross perovskite film and better electric contact at the PVK/ZnO interface. As a result, the optimized PSCs deliver a champion PCE of 15.36% along with a stabilized power output (SPO) of 15.05%. Meanwhile, these PSCs also display excellent long-term operational stability under ambient conditions. This work thus provides a feasible route for improving the performance and stability of inverted PSCs.

A counter electrode modified with renewable carbonized biomass for an all-inorganic CsPbBr3 perovskite solar cell

The cost associated with hole-transporting materials (HTMs) and electrodes made of noble metals is a recurrent problem for the widespread application of perovskite solar cells (PSCs). Biomass-derived carbons are green materials that have been incorporated in the electrodes of diverse electrochemical devices to reduce cost, improve environmental sustainability, and augment the specific surface area (SSA). Here, carbonized bacterial cellulose (CBC) and carbonized macadamia nutshell (CMNS) were combined with commercial carbon paste (CP) to fabricate counter electrodes (CEs) integrated into highly-stable all-inorganic CsPbBr3 PSCs synthesized by thermal evaporation. When electrically-conductive CP was mixed with either 0.1% CBC or CMNS, the power conversion efficiency was improved to 4.76% and 6.18%, respectively, compared to 4.45% for a PSC equipped with pure CP. The better performance of CMNS versus CBC in the CEs can be explained by a larger SSA, a more suitable work function, and a lower sheet resistance. The outstanding surface area of CMNS is likely to improve hole scavenging efficiency in the PSCs by increasing the number of contacts with CsPbBr3. The long-term stability of the all-inorganic CsPbBr3 PSC at high temperature was also improved with the CP CE modified with CMNS. These results demonstrate that adding CBC or CMNS to CP for the fabrication of CEs in a suitable ratio improves the photoelectric properties of all-inorganic PSCs and thus opens possibilities for novel applications for renewable and earth-abundant biomass-derived carbons.

Crystallization kinetics modulation and defect suppression of all-inorganic CsPbX3 perovskite films

The recent research progress in film quality optimization strategies and the investigations of the film formation mechanism in all-inorganic CsPbX3 perovskite solar cells are systematically reviewed.

Effectively Inhibit Phase Separation to Improve Efficiency and Stability of All-Inorganic Planar CsPbIBr2 Perovskite Solar Cells

Effectively Inhibit Phase Separation to Improve Efficiency and Stability of All-Inorganic Planar CsPbIBr2 Perovskite Solar Cells

High-quality and full-coverage CsPbBr3 thin films via electron beam evaporation with post-annealing treatment for all-inorganic perovskite solar cells

Due to their superior stability in comparison to organic–inorganic hybrid devices, all-inorganic cesium lead bromide (CsPbBr3) perovskite solar cells (PSCs) have garnered considerable attention. However, the conventional solution process is limited for the preparing of CsPbBr3 films due to the limitation of bromide in solution, resulting in uneven film and low coverage. So, the development of viable evaporation deposition strategies is essential for boosting the power conversion efficiency (PCE) of CsPbBr3-based PSCs. In this work, high-quality and full-coverage CsPbBr3 thin films are fabricated using single-source electron beam evaporation followed with post-annealing treatment. Br-rich condition in evaporation process is realized by using the mixture of CsPbBr3 and Cs4PbBr6 powders as source materials, and the formation of CsPb2Br5 phase is successfully suppressed. Furthermore, the influences of annealing temperature and annealing time on the crystallinity, morphology and optical properties of the films are thoroughly explored. High-quality CsPbBr3 films with good uniformity and crystallinity are achieved by systematic optimization of the annealing parameters. As a result, a device efficiency of 7.81% with an open circuit voltage (VOC) of 1.43 V has been achieved for the PSCs with a planar structure of FTO/c-TiO2/CsPbBr3/carbon.

Nh4ac Boosts the Efficiency of Carbon-Based All-Inorganic Perovskite Solar Cells Fabricated in the Full Ambient Air to 15.43%

Nh4ac Boosts the Efficiency of Carbon-Based All-Inorganic Perovskite Solar Cells Fabricated in the Full Ambient Air to 15.43%

A green Bi-Solvent system for processing high-quality CsPbBr3 films in efficient all-inorganic perovskite solar cells

All-brominated inorganic perovskite CsPbBr3 has received much attention in the field of optoelectronic applications owing to its superb stability and ease of manufacture under the ambient condition. However, the tedious process and toxic solvent are two major challenges for fabrication of CsPbBr3 films via a multi-step deposition method. Here, we demonstrate a sustainable bi-solvent system for preparing high-quality CsPbBr3 films in a triple-step solution-processed route, where the bi-solvent system comprises of green solvent water and ethylene glycol monomethyl ether (EGME) in place of the noxious methanol for CsBr solution. By adjusting the temperature of heat treatment and spin-coating speed, the pinhole-free, ultra-smooth and high crystallinity of CsPbBr3 films were obtained. As a result, the CsPbBr3 PSC prepared from the green bi-solvent system demonstrates an optimal power conversion efficiency (PCE) of 9.55%, which is one of the highest efficiencies for planar carbon-based PSCs without hole transport layer. Moreover, the all-inorganic unpacked PSCs exhibit excellent humidity stability under ambient environment for 34 days. Our result not only offers a facile and simple way to fabricate the pure-phase CsPbBr3 films, but also alleviates the solvent toxicity during the preparation of CsPbBr3 PSCs.

Ionic Liquid as an Additive for Two-Step Sequential Deposition for Air-Processed Efficient and Stable Carbon-Based CsPbI2Br All-Inorganic Perovskite Solar Cells

Ionic Liquid as an Additive for Two-Step Sequential Deposition for Air-Processed Efficient and Stable Carbon-Based CsPbI₂Br All-Inorganic Perovskite Solar Cells

On the role of carboxylated polythiophene in defect passivation of CsPbI 2 Br surface for efficient and stable all‐inorganic perovskite solar cells

Improved film surface is a prerequisite to achieve high photovoltaic performance of inorganic perovskite solar cells because defective (under-coordinated) lead ions derived from imperfect lattice structure of the film surface or grain boundaries the principal nonradiative recombination centers in the inorganic perovskite absorber. In this study, we suggest poly[3-(4-carboxybutyl)thiophene-2,5-diyl] (P3CT), a carboxylated p-type conjugated polymer, as a passivating agent of the CsPbI2Br layer to tailor electronic properties of a perovskite absorber. With the P3CT passivation, the defective sites of the perovskite film surface were improved and stabilized, which can suppress nonradiative recombination to promote charge transport of CsPbI2Br-based all-inorganic perovskite solar cells. Consequently, the P3CT passivation delivers a power conversion efficiency (PCE) of 12.25% and decent long-term stability of CsPbI2Br perovskite solar cells, which surpasses the pristine device without the passivation. The electricity generation capability under indoor light source of the passivated device is also studied, demonstrating a promising PCE of 27.47%. This work unveils the role of P3CT as a passivating agent to passivate the defective sites of CsPbI2Br perovskite film surface and grain boundaries, which facilitates charge transport and reduced carrier recombination of CsPbI2Br absorber in solar cell devices.

Phase Control of Cs-Pb-Br Derivatives to Suppress 0D Cs4 PbBr6 for High-Efficiency and Stable All-Inorganic CsPbBr3 Perovskite Solar Cells.

The precise phase control of Cs-Pb-Br derivatives from 3D CsPbBr3 to 0D Cs4 PbBr6 highly determines the photovoltaic performance of all-inorganic CsPbBr3 perovskite solar cells (PSCs). Herein, the preferred phase conversion from precursor to Cs-Pb-Br derivatives is revealed by theoretically calculating the Gibbs free energies (∆G) of various phase conversion processes, allowing for a simplified multi-step solution-processable spin-coating method to hinder the formation of detrimental 0D Cs4 PbBr6 phase and enhance the photovoltaic performance of a PSC because of its large exciton binding energy, which is regarded as a recombination center. By further accelerating the interfacial charge extraction with a novel 2D transition metal dichalcogenide ReSe2 , the hole-free CsPbBr3 PSC achieves a champion efficiency of 10.67% with an impressive open-circuit voltage of 1.622V and an excellent long-term stability. This work provides an in-depth understanding on the precise Cs-Pb-Br perovskite phase control and the effect of derivatives on photovoltaic performance of advanced CsPbBr3 PSCs.

Dual-functional metal (IIB) diethyldithocarbamate salts passivation enabled high-efficiency and stable carbon-based CsPbIBr2 all-inorganic perovskite solar cells

Solution-prepared perovskite films are accompanied by high defect density. Defects gathered on the surface or grain boundaries of the perovskite accelerate the degradation of the perovskite and affect the photovoltaic performance and long-term stability of the device, which is one of the bottlenecks to curb the further development of perovskite solar cells (PSCs). In this work, a simple and effective surface passivation method is designed by choosing metal (IIB) diethyldithiocarbamate salts [M(DDTC)2, M = Pb2+, Cd2+ and Zn2+]. The DDTC has excellent complexing ability with metal ions and chelate bidentately with unpaired Pb2+ ions on the surface of perovskite. IIB metal ions have a small ion radius and could easily diffuse into the perovskite to occupy Pb vacancies. The synergistic effect of anions and cations effectively reduces the defect concentration and non-radiative recombination in the CsPbIBr2 all-inorganic perovskite, thereby obtaining carbon-based CsPbIBr2 all-inorganic PSCs with high efficiency and high stability. Ultimately, champion efficiency of the Cd(DDTC)2 and Zn(DDTC)2 -treated CsPbIBr2 PSCs yield 9.59% and 10.21%, respectively, obviously higher than that of the pristine one (8.74%).

Improving the stability and scalability of all-inorganic inverted CsPbI2Br perovskite solar cell

All-inorganic perovskite solar cells (PSCs) have potential to pass the stability international standard of IEC61215:2016 but cannot deliver high performance and stability due to the poor interface contact. In this paper, Sn-doped TiO2 (Ti1−xSnxO2) ultrathin nanoparticles are prepared for electron transport layer (ETL) by solution process. The ultrathin Ti0.9Sn0.1O2 nanocrystals have greatly improved interface contact due to the facile film formation, good conductivity and high work function. The all-inorganic inverted NiOx/CsPbI2Br/Ti0.9Sn0.1O2 p-i-n device shows a power conversion efficiency (PCE) of 14.0%. We tested the heat stability, light stability and light-heat stability. After stored in 85 °C for 65 days, the inverted PSCs still retains 98% of initial efficiency. Under continuous standard one-sun illumination for 600 h, there is no efficiency decay, and under continuous illumination at 85 °C for 200 h, the device still retains 85% of initial efficiency. The 1.0 cm2 device of inverted structure shows a PCE of up to 11.2%. The ultrathin Ti1−xSnxO2 is promising to improve the scalability and stability and thus increase the commercial prospect.

Mitigating voltage loss in efficient CsPbI2Br all-inorganic perovskite solar cells via metal ion-doped ZnO electron transport layer

CsPbI2Br all-inorganic perovskite solar cells (PSCs) have attracted much attention due to their suitable bandgap and outstanding thermostability. However, the large energy loss of CsPbI2Br PSCs generally endows low open circuit voltage (VOC) and unsatisfactory power conversion efficiency (PCE), which severely hamper its further development. Herein, we proposed a facile route to modify the ZnO electron transporting layer (ETL) by in situ chemical doping strategy with metal ions. The doped ZnO ETL with Pb(Ac)2 or CsAc cannot only effectively tune its energy levels, conductivity, and charge extraction but also ameliorate the crystallization and morphology of upper perovskite films. Particularly, Pb(Ac)2-doped ZnO (ZnO:Pb) induces an energy level offset of 0.15 eV relative to the conduction band of CsPbI2Br with largely reduced Ohmic loss. Thus, the highest VOC is significantly boosted to above 1.3 V for the CsPbI2Br PSCs with a champion PCE of 16.36%, while the reference PSC just yields a moderate PCE of 14.43% with a low VOC of 1.168 V. Moreover, considerable improvements in device stability are achieved for the PSCs with doped ZnO ETLs than those of the ZnO-based device. Our work provides a promising strategy to alleviate the VOC deficit toward the attainment of highly efficient and stable PSCs.

Insights into the adsorption of water and oxygen on the cubic CsPbBr3 surfaces: A first-principles study

The degradation mechanism of the all-inorganic perovskite solar cells in the ambient environment remains unclear. In this paper, water and oxygen molecule adsorptions on the all-inorganic perovskite (CsPbBr3) surface are studied by density-functional theory calculations. In terms of the adsorption energy, the water molecules are more susceptible than the oxygen molecules to be adsorbed on the CsPbBr3 surface. The water molecules can be adsorbed on both the CsBr- and PbBr-terminated surfaces, but the oxygen molecules tend to be selectively adsorbed on the CsBr-terminated surface instead of the PbBr-terminated one due to the significant adsorption energy difference. While the adsorbed water molecules only contribute deep states, the oxygen molecules introduce interfacial states inside the bandgap of the perovskite, which would significantly impact the chemical and transport properties of the perovskite. Therefore, special attention should be paid to reduce the oxygen concentration in the environment during the device fabrication process so as to improve the stability and performance of the CsPbBr3-based devices.

Tailored graphene quantum dots to passivate defects and accelerate charge extraction for all-inorganic CsPbIBr2 perovskite solar cells

Graphene quantum dots (GQDs) have shown great potential to simultaneously improve the stability and efficiency of perovskite solar cells (PSCs). However, their preparation is either extremely harsh or inefficient, which severely hampers the extensive research and application. Herein, a novel solid-liquid interfacial exfoliation technique is established to fabricate high-quality GQDs from carbon fiber, in which the throughput of GQDs is up to 20 g in one pot with yield over 90%. To explore their role in PSC, nitrogen and sulfur functionalized GQDs have been further synthesized via a hydrothermal method, and used to regulate the interfacial properties of all-inorganic CsPbIBr2 PSC. Arising from the interaction based on Lewis acid-base chemistry between GQDs and the under-coordinated Pb2+, the detrimental non-radiative recombination is significantly reduced, especially for the functionalized GQDs tailored PSC, leading to the champion efficiency of 9.80% for carbon-electrode based CsPbIBr2 PSCs with excellent long-term stability.

CsCl-induced defect control of CsPbI2Br thin films for achieving open-circuit voltage of 1.33 V in all-inorganic perovskite solar cells

All-inorganic perovskite solar cells (PSCs) attract attention due to their excellent optical properties and high thermal stability, but energy loss is a challenge due to the trap-assisted recombination loss at the imperfect film morphology. We herein demonstrate the optimization of α-CsPbI2Br morphology including low defect density and large grain size by employing cesium chloride (CsCl) as an additive. High-quality CsPbI2Br film grown with CsCl reveals high crystallinity and largely-grained morphology, which provides reduced defect density and energy loss. As a result, we optimize the CsPbI2Br device with 1% CsCl additive, which shows a power conversion efficiency (PCE) of 11.04% with an open-circuit voltage (VOC) of 1.33 V. The CsPbI2Br with CsCl shows stability maintaining >80% of the initial efficiency being aged for >360 h in ambient atmosphere. The CsCl-employed device also retains 98% of initial PCE after being heated at 85 °C for 12 h, verifying enhanced stability of the all-inorganic PSCs. In addition, the photovoltaic performance under white light-emitting diode yields PCE over 25% with a high V OC of 1.08 V in the presence of CsCl, which realizes the stable all-inorganic PSCs applicable in outdoor/indoor environments.

Enhancing the performance and stability of carbon-based CsPbI2Br perovskite solar cells via tetrabutylammonium iodide surface passivation

All-inorganic carbon-based perovskite solar cells (C-PSCs) with CsPbI2Br as photosensitizer have attracted great attention due to their low cost, high efficiency, and good stability. However, the CsPbI2Br film prepared by the solution method usually has many defects, which reduces the charge extraction rate and photoelectric performance. In this paper, intermediate gradient annealing and antisolvent ethyl acetate treatment are combined to prepare CsPbI2Br films with good crystallinity and few voids. The surface of the obtained CsPbI2Br film is then treated using tetrabutylammonium iodide (TBAI), which can interact with the Pb-I framework to passivate defect states and extend the carrier lifetime. Finally, the champion power conversion efficiency (PCE) of the optimized C-PSCs with a structure of FTO/SnO2/CsPbI2Br/carbon electrode prepared in the air reach 12.29%. At the same time, TBAI molecules also effectively enhance the stability of the PSCs, and the unencapsulated device can still maintain 90% of the initial efficiency after 300 h of storage in an ambient air atmosphere with a relative humidity of 20%-30%. This work provides a simple and effective strategy for the preparation of cheap, high-performance, and stable all-inorganic C-PSCs under atmospheric conditions, and also increases the feasibility of PSCs commercialization.

Generic water-based spray-assisted growth for scalable high-efficiency carbon-electrode all-inorganic perovskite solar cells

SummaryA water-based spray-assisted growth strategy is proposed to prepare large-area all-inorganic perovskite films for perovskite solar cells (PSCs), which involves in spraying of cesium halide water solution onto spin-coating-deposited lead halide films, followed by thermal annealing. With CsPbBr3 as an example, we show that as-proposed growth strategy can enable the films with uniform surface, full coverage, pure phase, large grains, and high crystallinity, which primarily benefits from the controllable CsBr loading quantity, and the use of water as CsBr solvent makes the reaction between CsBr and PbBr2 immune to PbBr2 film microstructure. As a result, the small-area (0.09 cm2) and large-area (1.00 cm2) carbon-electrode CsPbBr3 PSCs yield the record-high efficiencies of 10.22% and 8.21%, respectively, coupled with excellent operational stability. We also illustrate that the water-based spray-assisted deposition strategy is suitable to prepare CsPbCl3, CsPbIBr2, and CsPbI2Br films with outstanding efficiencies of 1.27%, 10.44%, and 13.30%, respectively, for carbon-electrode PSCs.

A Universal Dopant-Free Polymeric Hole-Transporting Material for Efficient and Stable All-Inorganic and Organic-Inorganic Perovskite Solar Cells.

Hole-transporting materials (HTMs) with desired properties play a crucial role in achieving efficient and stable perovskite solar cells (PSCs). However, most high-performance devices generally employ HTMs that require additional complicated doping treatments, which are harmful to the device stability. In this work, a fluorine-substituted polymer electron-donor material, PM6, is developed as a dopant-free HTM in regular all-inorganic CsPbI2Br PSCs. Benefiting from the matched energy-level alignment, high hole mobility, and effective defect passivation, a champion power conversion efficiency (PCE) of 16.06% with an ultrahigh fill factor of 82.54% is achieved for the PM6-based PSCs. Compared to doped Spiro-OMeTAD (PCE of 14.46%), PM6 significantly enhances the PCE of CsPbI2Br PSCs with negligible hysteresis owing to its more efficient charge transportation, suppressed recombination, and strong trap passivation effect. Moreover, remarkable improvements in long-term stability, thermal stability, and operational stability are all gained for the PM6-based PSCs. In addition, the successful application of PM6 as a dopant-free HTM in organic-inorganic hybrid PSCs enables an impressive PCE of 20.05% with superb device stability, manifesting the generality of the polymer donor material in various PSC systems.

Organic additives in all-inorganic perovskite solar cells and modules: from moisture endurance to enhanced efficiency and operational stability

Power conversion efficiency (PCE) of perovskite solar cells (PSC) has been skyrocketed to certified 25.5% owing to their improved and tunable optoelectronic properties. Although, various strategies have been adopted to date regarding PCE and stability enhancement within PSC technology, certain instability factors (moisture, heat, light) are hindering their commercial placement. Recently, all-inorganic PSCs got hype in the photovoltaic research community after they attained PCE > 20% and due to their significant endurance against heat and light mishmashes, but there only left moisture sensitivity as the only roadblock for their industrial integration. Here, we review the recent progress of additive inclusion into all-inorganic (CsPbX3) PSCs to stabilize their intrinsic structure and to withstand the performance limiting factors. We start with the detailed description of chemical instability of different perovskite compositions, phase segregation, and how organic molecules and dyes help to repair the structural defects to improve the overall PCE and stability of PSCs. Moisture endurance as a result of chemical passivation through organic additives, low-dimensional inorganic PSCs to enhance device stability and scalable fabrication of CsPbX3 PSCs are also reviewed. The challenges of module degradation and design implications with proposed strategies and outlook are interpreted in the ending phrases of this review.