Search

Outstanding material properties allowed perovskite solar cells’ power conversion efficiencies (PCEs) exceed 25% within a decade, demonstrating the most rapid increase rate in PCEs among all the existing photovoltaic (PV) technologies. Despite such significant progress perovskite technology commercialization requires further enhancement in device performance. Here, we report a strategy for optimizing interfacial quality of the perovskite solar cells (PSCs). The interfacial layer between the electron transport layer (ETL) and the perovskite absorber were optimized by interface engineering technique via preparing the ETL consisted of Tin(IV) oxide (SnO2) quantum dots (QDs), SnO2 nanoparticle (NP) and a passivation layer based on Poly(methyl methacrylate): [6,6]-phenyl-C61-butyric acid methyl ester (PMMA:PCBM). It was demonstrated that the PSCs with a single-layer ETL made of SnO2 QDs exhibit strong I-V hysteresis, while the application of a triple-layer ETL effectively suppresses the hysteresis due to the optimization of ETL/perovskite interface. This work demonstrated the effective protocol which can substantially improve the performance of PSCs and eliminate the I-V hysteresis.

In the conventional sandwich structure of perovskite solar cells (PSCs) with the metallic electrodes, the parasitic absorption losses due to the presence of glass substrate, conductive metal oxides and other functional layers below the perovskite film reduce a certain portion of photons that can be harvested by the perovskite absorber. The carbon quantum dots (CQDs) with down-converting properties can absorb high-energy UV light and convert them into the photons with lower energy lying in the visible light region. The CQDs can be used to enhance the light harvesting power of the PSCs so that the negative effect due to the parasitic absorption can be suppressed. In this work, a coating layer composed of CQDs is deposited on the illuminated side of the glass substrate. In contrast to our previous report, the deionized water (DIW) is used to disperse the CQDs instead of dispersing CQDs in the matrix of PMMA and chlorobenzene (CB). By using the new approach, the preparation of CQD coatings is more efficient and the use of toxic CB can be avoided. After systematic optimization of the preparation parameters, it is found that using water as the dispersion medium for CQDs can also yield the effective coatings for PSCs to enhance their light absorption power.

This work reports the impact of electron transport layers (ETLs) on the performance of perovskite solar cells (PSCs). The ETLs are based on tin (IV) oxide (SnO 2 ) prepared in different nanostructures. The carrier transport properties of PSCs are systematically characterized and the underlying mechanism for the enhancement in performance of PSCs is found. The strategies for optimizing the interface between the ETL and perovskite are demonstrated, yielding a champion device with a power conversion efficiency (PCE) of 20.8 %.

Perovskite solar cells (PSCs) with a standard sandwich structure suffer from optical transmission losses due to the substrate and its active layers. Developing strategies for compensating for the losses in light harvesting is of significant importance to achieving a further enhancement in device efficiencies. In this work, the down-conversion effect of carbon quantum dots (CQDs) was employed to convert the UV fraction of the incident light into visible light. For this, thin films of poly(methyl methacrylate) with embedded carbon quantum dots (CQD@PMMA) were deposited on the illumination side of PSCs. Analysis of the device performances before and after application of CQD@PMMA photoactive functional film on PSCs revealed that the devices with the coating showed an improved photocurrent and fill factor, resulting in higher device efficiency.

The performance of perovskite solar cells (PSCs) are determined by a number of factors including the quality of perovskite absorber, types of the carrier transports layers and the interfacial quality between the perovskite thin film and carrier transport layers. This work demonstrates effective fabrication strategies focusing on the mixed perovskites and electron transport layers (ETLs). A novel cryogenic-assisted technique is used to grow high-quality mixed perovskite thin films. The performance of PSCs based on SnO 2 ETL is found to be more promising compared to the commonly used TiO 2 , in terms of power conversion efficiency (PCE) and light stability. To achieve hysteresis-free PSCs, the architecture of the electron transport layers should be also carefully optimized.

This work demonstrates the effectiveness of interfacial engineering and defect passivation in the bulk of mixed perovskite absorber to achieve high performance perovskite solar cells (PSCs). It is found that the extent of I–V hysteresis is most significant in PSCs with a single-layer electron transport layer (ETL) composed of SnO2 quantum dots (QD-SnO2) or SnO2 nanoparticles (NP–SnO2). The hysteresis of the PSCs can be effectively suppressed by adopting a multilayer structure for the ETL to optimize the ETL/perovskite interface. Furthermore, the performance of the PSCs can be enhanced by incorporating a controlled amount of an organic cross linker, 2,2′-(ethylenedioxy)bis (ethylammonium iodide) (EDAI), in the mixed perovskite absorber layers. The experimental results consistently show that incorporation of an optimal amount of EDAI is effective in passivating defect states in the bulk of mixed perovskite as well as the grain boundaries and film surface, while excessive EDAI significantly degrades the photovoltaic (PV) performance of PSCs due to generation of defects and electrically insulating properties of EDAI itself. Owing to the synergistic effect contributed from optimized ETL/perovskite interface and the mixed perovskite thin film, the PSC with an active area of 0.06 cm2 exhibits a champion power conversion efficiency (PCE) of ~19.0% with negligible hysteresis and improved stability. The proposed strategies were also applied to fabricate larger area devices from 0.15 cm2 to 0.85 cm2, exhibiting the PCEs of ~12%–18% with negligible hysteresis.

Organic photovoltaics has attracted much effort and many research groups during the past decade, because of low-cost and easy fabrication techniques. Despite the great progress that has been achieved in increasing the conversion efficiencies of the devices, there are still several problems to be solved to make the solar cells commercially viable, especially for cells based on bulk heterojunctions.The purpose of this work is to supply techniques for predicting the order of magnitude of the charge carrier mobilities of bulk heterojunction devices, on the basis of easy-to-perform measurements for experimentalists. A one dimensional model of a bulk heterojunction cell was used, and then simulations were performed in order to obtain the photocurrent as a function of an effective applied voltage. Plotted in a double logarithmic scale, the resulting curves exhibit different signatures depending on the mobilities of the charge carriers. These signatures could be helpful for experimentalists in order to predict an order of magnitude for both the electron mobility and the hole mobility.