Efficient and Stable Large-Area Perovskite Solar Cells with Inorganic Perovskite/Carbon Quantum Dot-Graded Heterojunction.
ABSTRACT: This work reports on a compositionally graded heterojunction for photovoltaic application by cooperating fluorine-doped carbon quantum dots (FCQDs in short) into the CsPbI2.5Br0.5 inorganic perovskite layer. Using this CsPbI2.5Br0.5/FCQDs graded heterojunction in conjunction with low-temperature-processed carbon electrode, a power conversion efficiency of 13.53% for 1 cm2 all-inorganic perovskite solar cell can be achieved at AM 1.5G solar irradiation. To the best of our knowledge, this is one of the highest efficiency reported for carbon electrode based all-inorganic perovskite solar cells so far, and the first report of 1 cm2 carbon counter electrode based inorganic perovskite solar cell with PCE exceeding 13%. Moreover, the inorganic perovskite/carbon quantum dot graded heterojunction photovoltaics maintained over 90% of their initial efficiency after thermal aging at 85° for 1056 hours. This conception of constructing inorganic perovskite/FCQDs graded heterojunction offers a feasible pathway to develop efficient and stable photovoltaics for scale-up and practical applications.
Project description:All-inorganic CsPbI<sub>3</sub> perovskite quantum dots have received substantial research interest for photovoltaic applications because of higher efficiency compared to solar cells using other quantum dots materials and the various exciting properties that perovskites have to offer. These quantum dot devices also exhibit good mechanical stability amongst various thin-film photovoltaic technologies. We demonstrate higher mechanical endurance of quantum dot films compared to bulk thin film and highlight the importance of further research on high-performance and flexible optoelectronic devices using nanoscale grains as an advantage. Specifically, we develop a hybrid interfacial architecture consisting of CsPbI<sub>3</sub> quantum dot/PCBM heterojunction, enabling an energy cascade for efficient charge transfer and mechanical adhesion. The champion CsPbI<sub>3</sub> quantum dot solar cell has an efficiency of 15.1% (stabilized power output of 14.61%), which is among the highest report to date. Building on this strategy, we further demonstrate a highest efficiency of 12.3% in flexible quantum dot photovoltaics.
Project description:In this article, we present a new paradigm for organometallic hybrid perovskite solar cell using NiO inorganic metal oxide nanocrystalline as p-type electrode material and realized the first mesoscopic NiO/perovskite/[6,6]-phenyl C61-butyric acid methyl ester (PC61BM) heterojunction photovoltaic device. The photo-induced transient absorption spectroscopy results verified that the architecture is an effective p-type sensitized junction, which is the first inorganic p-type, metal oxide contact material for perovskite-based solar cell. Power conversion efficiency of 9.51% was achieved under AM 1.5 G illumination, which significantly surpassed the reported conventional p-type dye-sensitized solar cells. The replacement of the organic hole transport materials by a p-type metal oxide has the advantages to provide robust device architecture for further development of all-inorganic perovskite-based thin-film solar cells and tandem photovoltaics.
Project description:Vacuum deposition is a simple and controllable approach that aims to form higher-quality perovskite films compared with those formed using solution-based deposition processes. Herein, we demonstrate a novel method to promote the intercalation control of inorganic cesium lead iodide (CsPbI<sub>3</sub>) perovskite thin films via alternate vacuum deposition. We also investigated the effect of layer-by-layer deposition of PbI<sub>2</sub>/CsI to fabricate efficient planar heterojunction CsPbI<sub>3</sub> thin films and solar cells. This procedure is comparatively simple when compared with commonly used coevaporation techniques; further, precise intercalation control of the CsPbI<sub>3</sub> thin films can be achieved by increasing the number of layers in the layer-by-layer deposition of PbI<sub>2</sub>/CsI. The best control and the highest reproducibility were achieved for the deposition of four double layers owing to the precise intercalation control during the deposition of the CsPbI<sub>3</sub> thin film. A power conversion efficiency of 6.79% was obtained via alternating vacuum deposition of two double layers with a short-circuit current density (<i>J</i> <sub>sc</sub>) of 12.06 mA/cm<sup>2</sup>, an open-circuit voltage (<i>V</i> <sub>oc</sub>) of 0.79 V, and a fill factor (FF) of 0.72. Our results suggest a route for inorganic precursors to be used for efficient perovskite solar cells via alternating vacuum deposition.
Project description:Among various all-inorganic halide perovskites exhibiting better stability than organic-inorganic halide perovskites, α-CsPbI<sub>3</sub> with the most suitable band gap for tandem solar cell application faces an issue of phase instability under ambient conditions. We discovered that a small amount of two-dimensional (2D) EDAPbI<sub>4</sub> perovskite containing the ethylenediamine (EDA) cation stabilizes the α-CsPbI<sub>3</sub> to avoid the undesirable formation of the nonperovskite δ phase. Moreover, not only the 2D perovskite of EDAPbI<sub>4</sub> facilitate the formation of α-CsPbI<sub>3</sub> perovskite films exhibiting high phase stability at room temperature for months and at 100°C for >150 hours but also the α-CsPbI<sub>3</sub> perovskite solar cells (PSCs) display highly reproducible efficiency of 11.8%, a record for all-inorganic lead halide PSCs. Therefore, using the bication EDA presents a novel and promising strategy to design all-inorganic lead halide PSCs with high performance and reliability.
Project description:Inorganic halide perovskites such as cesium lead halide are promising due to their excellent thermal stability. Cesium lead iodide (CsPbI<sub>3</sub>) has a bandgap of 1.73?eV and is very suitable for making efficient tandem solar cells, either with low-bandgap perovskite or silicon. However, the phase instability of CsPbI<sub>3</sub> is hindering the further optimization of device performance. Here, we show that high quality and stable ?-phase CsPbI<sub>3</sub> film is obtained via solvent-controlled growth of the precursor film in a dry environment. A 15.7% power conversion efficiency of CsPbI<sub>3</sub> solar cells is achieved, which is the highest efficiency reported for inorganic perovskite solar cells up to now. And more importantly, the devices can tolerate continuous light soaking for more than 500?h without efficiency drop.
Project description:A 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 CsPbBr<sub>3</sub> 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 PbBr<sub>2</sub> immune to PbBr<sub>2</sub> film microstructure. As a result, the small-area (0.09 cm<sup>2</sup>) and large-area (1.00 cm<sup>2</sup>) carbon-electrode CsPbBr<sub>3</sub> 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 CsPbCl<sub>3</sub>, CsPbIBr<sub>2</sub>, and CsPbI<sub>2</sub>Br films with outstanding efficiencies of 1.27%, 10.44%, and 13.30%, respectively, for carbon-electrode PSCs.
Project description:The emerging CsPbI<sub>3</sub> perovskites are highly efficient and thermally stable materials for wide-band gap perovskite solar cells (PSCs), but the doped hole transport materials (HTMs) accelerate the undesirable phase transition of CsPbI<sub>3</sub> in ambient. Herein, a dopant-free D-π-A type HTM named CI-TTIN-2F has been developed which overcomes this problem. The suitable optoelectronic properties and energy-level alignment endow CI-TTIN-2F with excellent charge collection properties. Moreover, CI-TTIN-2F provides multisite defect-healing effects on the defective sites of CsPbI<sub>3</sub> surface. Inorganic CsPbI<sub>3</sub> PSCs with CI-TTIN-2F HTM feature high efficiencies up to 15.9 %, along with 86 % efficiency retention after 1000 h under ambient conditions. Inorganic perovskite solar modules were also fabricated that exhibiting an efficiency of 11.0 % with a record area of 27 cm<sup>2</sup> . This work confirms that using efficient dopant-free HTMs is an attractive strategy to stabilize inorganic PSCs for their future scale-up.
Project description:All-inorganic perovskites have a special place in halide perovskite family because of their potential for better stability. However, the representative cesium lead iodide (CsPbI<sub>3</sub>) is metastable and spontaneously converts to the non-perovskite structure at room temperature. Here, we demonstrate that what appears to be all-inorganic CsPbI<sub>3</sub> stabilized in its perovskite form using the purported intermediate known as hydrogen lead iodide (HPbI<sub>3</sub>) is, in fact, the hybrid perovskite cesium dimethylammonium lead iodide (Cs<sub>1-x</sub>DMA<sub>x</sub>PbI<sub>3</sub>, x = 0.2 to 0.5). Thus, many of the reported all-inorganic perovskites are actually still hybrid organic-inorganic perovskites, as strongly evidenced by a wide battery of experimental techniques presented here. Solar cells based on the representative composition Cs<sub>0.7</sub>DMA<sub>0.3</sub>PbI<sub>3</sub> can achieve an average power conversion efficiency of 9.27 ± 1.28% (max 12.62%). These results provide an alternative angle to look at previous results pertaining all-inorganic CsPbI<sub>3</sub> while the DMA cation is now revealed as an alternative A site cation.
Project description:Photovoltaic cells use semiconductors to convert sunlight into electrical current and are regarded as a key technology for a sustainable energy supply. Quantum dot-based solar cells have shown great potential as next generation, high performance, low-cost photovoltaics due to the outstanding optoelectronic properties of quantum dots and their multiple exciton generation (MEG) capability. This review focuses on QDs as light harvesters in solar cells, including different structures of QD-based solar cells, such as QD heterojunction solar cells, QD-Schottky solar cells, QD-sensitized solar cells and the recent development in organic-inorganic perovskite heterojunction solar cells. Mechanisms, procedures, advantages, disadvantages and the latest results obtained in the field are described. To summarize, a future perspective is offered.
Project description:All-inorganic perovskites have been intensively investigated as potential optoelectronic materials because of their excellent thermal stability, especially for CsPbI<sub>2</sub> Br. Herein, the authors studied the effects of mixed passivation utilizing organic phenylethylammonium bromide and inorganic ionic cesium bromide (PEABr + CsBr) on the all-inorganic perovskite (CsPbI<sub>2</sub> Br) solar cells for the first time. The treatment with different passivation mechanisms enhances the perovskite film quality, resulting in uniform surface morphology and compact film with low trap density. Besides, the passivation improves the energy level alignment, which benefits the hole extraction at the perovskite/HTL interface and drives the interface electron separation, suppressing the charge recombination and realizing a high open-circuit voltage (V<sub>oc</sub> ). Finally, the device represents a high power conversion efficiency (PCE) of 16.70%, a V<sub>oc</sub> of 1.30 V, and an excellent fill factor (FF) of 0.82. The V<sub>oc</sub> loss and high FF should be among the best values for CsPbI<sub>2</sub> Br based devices. Furthermore, the treated devices exhibit remarkable long-term stability with only 8% PCE loss after storing in a glove box for more than 1000 h without encapsulation.