• Energy Research

We proposed a novel application of cobalt sulfide (CoS) in the configuration of transparent thin film as anode in p-type dye-sensitized solar cell (p-DSC). The anodes here considered have been prepared using a water-based method that is suitable for the large scale production of large-area electrodes. The photoactive cathodes of the p-DSC were mesoporous nickel oxide (NiO) thin films deposited via rapid discharge sintering. The NiO electrodes were sensitized with the benchmark dye erythrosine B (ERY), while the couple I−/I3− was the redox mediator. The CoS anodes showed higher electrocatalytic efficiency in comparison with the commonly used platinized Fluorine-doped Tin Oxide (Pt-FTO). This was determined by means of electrochemical impedance spectroscopy of CoS based dummy cells, with CoS showing a lower charge-transfer resistance with respect to Pt-FTO. The overall conversion efficiency of the p-DSC employing ERY-sensitized NiO as photoactive cathode and CoS anode was 0.026 %, a value very close to that obtained with Pt-FTO anodes (0.030 %). The external quantum efficiency spectra of the p-DSCs with CoS anodes were similar to those obtained with Pt-FTO anodes under illumination with AM 1.5 solar simulator.

Abstract We carried out an investigation on the performance of a conformal curved large area, flexible, metal/plastic dye solar cells in outdoor conditions. We calculated the energy produced by the flexible cells over the course of a diurnal cycle utilizing their peculiar property of being able to be conformed to curved surfaces. The total electrical energy E produced and energy produced per unit of occupied surface (i.e. footprint) E ∗ over the course of a whole day were extracted from flat cells placed facing South with a 60° tilt angle and also for cells conformal to a cylindrical curve surface. For RCURV = 13.5 cm an enhancement of 3.3% and 7.9% respectively for E and E ∗ was observed with respect to the cell positioned flat. The enhancement in E ∗ was even greater (9.1%) when RCURV = 5.5 cm. Mechanisms induced by curving the device and leading to this enhancement were analyzed. These results that show up to ∼10% enhancement of energy produced (per unit of occupied projected area) compared to flat devices demonstrate the attractiveness and possibilities of DSC technology for all those applications where devices handiness, flexibility and conformability are required.

We present our research for fast and reliable extraction of bandgap and absorption quality values for triple-cation perovskite thin films from sample scans. Our approach leverages machine learning methods, namely convolutional neural networks, to perform regression tasks aimed at predicting the properties of interest. To this end, thin film samples were synthesized via blade-coating and their photoluminescence and ultraviolet–visible spectra collected, along with the film thickness. We propose a method of computing a dimensionless figure of merit we called the Area Under Absorption Coefficient (AUAC), its purpose being to qualitatively evaluate the absorption quality of perovskite films for use in photovoltaic modules. This work demonstrates the usability of simple imaging techniques to analyze experimental samples while requiring only a feasibly acquirable initial amount of data. Our reported method can help speed up time consuming material optimizations by reducing lab time spent on recurrent characterization, nicely synergizes with high throughput production lines and could be adapted for quick extraction of other optoelectrical quantities.

In the renewable energy field, the use of hybrid perovskite materials has opened up new directions to fabricate cost‐effective and highly efficient photovoltaic devices. Despite impressive power conversion efficiency (PCE), exceeding 25.2%, demonstrated on lab‐scale devices, scalability and stability of device are still topical issues. In this context, large‐area deposition procedures and automated fabrication protocols are required to achieve high throughput serial production of modules and panels. In this work, a spray‐coated tin oxide (SnO2) layer processed at low temperature for the realization of planar perovskite solar cells (PSCs) and modules is demonstrated. Using sprayed Np‐SnO2 as the electron transport layer (ETL), a CH3NH3PbI3‐based solar device shows a maximum PCE of 16.77% (avg. 15.01%) comparable to 17% (avg. 15.5%) with respect to spin‐coated Np‐SnO2. Unencapsulated spray‐ and spin‐coated PSCs stored in 25 °C and 50% relative humidity show shelf life stability by retaining 85% of the initial PCE value after more than 1000 h. Moreover, the feasibility of fabrication of the modules with 15 cm2 active area is demonstrated, which reaches 9.37% of PCE from uniform spray‐deposited SnO2 film on a large area (20 × 20 cm2).

ABSTRACTWe have analysed and optimised a laser process for the sintering of the TiO2 layers in dye solar cells (DSCs). Through a thermographic characterisation of the process, we show that it is possible to scale and process large areas uniformly (16 cm2). We fabricated DSCs with nanocrystalline (nc)‐TiO2 films sintered by using pulsed ultraviolet laser with an average output power P varying from 1 W to 7 W whilst mainting a constant power conversion efficiency η. The highest efficiency reached for a laser sintered DSC was 7%. The time required to sinter 1 m2 of nc‐TiO2 film was found to decrease hyperbolically with P, which is important for determining process takt times. We quantified the embodied energy (EE) required to sinter 1 m2 of the active TiO2 layer for a variety of different processes, and found that the EE for the laser sintering process with a system wall plug efficiency of 3.5% to be competitive with the more conventional oven and belt furnace treatments. We outline the main features required from a laser system to carry out an efficient, energetically favourable and industrially applicable automated process with competitive throughput. Copyright © 2012 John Wiley & Sons, Ltd.

Today poly and mono-crystalline silicon dominate the photovoltaic (PV) markets for outdoor applications. Nevertheless, there is a growing requirement for PV to be deployed in a wide variety of conditions from building-integrated, to portable electronics, to indoors for powering smart sensors, internet of things and homes. In this latter environment, other PV technologies such as amorphous silicon and dye sensitized solar cells have been the wide-spread choice to date for light harvesting. Here, we show that the perovskite solar cells (PSCs) we developed, in their mesoscopic form, incorporating both low temperature compact and mesoporous TiO2 layers, possess an outstanding combination of high power conversion efficiency (PCE) under both outdoor and indoor illumination conditions: i.e. PCE=15.9% (the highest for low temperature processed PSC in the mesoscopic form) under Standard Test Conditions (STC:1000 W/m2 with AM 1.5 Spectrum, 25 °C), and PCE=24% − 25.4% under indoor lighting (with a Maximum Power Density MPD=15.4 µW cm−2 at 200 lx and 32.6 µW cm−2 at 400 lx under compact fluorescent lamp). Our results demonstrate this technology to be exceptional for all-round performance, furthermore being manufactured via low-cost processing. These state-of-the-art high values were enabled by the development of high quality thin TiO2 layers deposited by atomic layer deposition (ALD). Furthermore, our investigation highlights the more stringent blocking behavior requirements of the compact layers under low-level light illumination compared to when the device has to operate under STC. Finally, the architecture and processes used were all carried out at low temperatures (T<150 °C) which enabled us to successfully transfer the design to plastic substrates.

Ultrafast pump-probe spectroscopies have proved to be an important tool for the investigation of charge carriers dynamics in perovskite materials providing crucial information on the dynamics of the excited carriers, and fundamental in the development of new devices with tailored photovoltaic properties. Fast transient absorbance spectroscopy on mixed-cation hybrid lead halide perovskite samples was used to investigate how the dimensions and the morphology of the perovskite crystals embedded in the capping (large crystals) and mesoporous (small crystals) layers affect the hot-carrier dynamics in the first hundreds of femtoseconds as a function of the excitation energy. The comparative study between samples with perovskite deposited on substrates with and without the mesoporous layer has shown how the small crystals preserve the temperature of the carriers for a longer period after the excitation than the large crystals. This study showed how the high sensitivity of the time-resolved spectroscopies in discriminating the transient response due to the different morphology of the crystals embedded in the layers of the same sample can be applied in the general characterization of materials to be used in solar cell devices and large area modules, providing further and valuable information for the optimization and enhancement of stability and efficiency in the power conversion of new perovskite-based devices.