Improving the stability, aesthetics and performance of perovskite materials for photovoltaics

Lead Research Organisation: Swansea University
Department Name: School of Engineering

Abstract

The generation of energy is the most important scientific and technological challenge that faces humankind in the 21st century. In order to supply the demand of increasing global energy requirements, the development of low cost, easily processable, efficient photovoltaics (PV) is essential. Third generation PV offers a potentially low cost, easily processable and efficient technology and before us lays a great opportunity in solar energy research. International progress in PV research and technology is currently running at an unparalleled rate, with major contributions from the SPECIFIC and Ser Solar groups. The extremely rapid evolution of solution processed halide perovskite-based solar cells during the last few years (reaching efficiencies in the range of 15-20%, including certified 20.1%) makes them an extremely strong candidate to develop a cost and performance competitive PV technology. Photovoltaic devices which utilise light harvesting perovskite chemistries could potentially offer a cheaper and simpler technology in comparison to the typically favoured silicon solar cell. However, current issues when using perovskites for PV application include physicochemical degradation, instability and lifetime issues up on exposure to ambient conditions. The fundamental workings and reasoning for the aforementioned problems when using perovskite absorbers are yet to be fully understood. The project is concerned with gaining a better understanding of halide perovskite chemistry through identification and investigation of the manufacturing conditions or parameters which may lead to device instabilities. Fluorescence microscopy and fluorescence spectroscopy are two techniques which will be applied to investigate the photoluminescent properties and morphologies of a range of perovskite materials prepared under different conditions. The project research will explore routes to increasing the efficiency and light harvesting ability of these devices. There is also scope to use X-ray diffraction to investigate the crystalline structure of the perovskite layer and to determine whether the uniformity of this layer (amongst other layers) is affected by the alteration of certain parameters during device manufacture. The degradation of perovskite is believed to be exacerbated due to reaction with oxygen which will be investigated using transient absorption spectroscopy as a method to monitor oxygen diffusion within halide-perovskite solar cells. The overall aim is to develop an understanding of device photophysics and photochemistry resulting in the development of new materials to improve stability and cost and leading to world leading, high impact articles in the premier international journals in the field.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509553/1 01/10/2016 30/09/2021
1879632 Studentship EP/N509553/1 01/01/2017 30/06/2020 Tamara Dee McFarlane
 
Description Lead halide perovskites (CH3NH3)PbX3 (X = Cl, Br or I) offer a versatile and performance effective photovoltaic (PV) material with the potential to become an eminent competitor within the PV sector. This research aspires to develop an understanding of both the photochemistry of methylammonium lead bromide (CH3NH3PbBr3) perovskite and methylammonium lead iodide (CH3NH3PbI3) photovoltaic devices through the exploration of routes which may increase the efficiency and light harvesting ability of such devices.
The initial aims of this research included improving and optimising the manufacturing method of CH3NH3PbBr3 devices to consistently achieve device efficiencies of or above at least 1%. This was with a view to co-sensitising the devices with blue/green sensitising dyes which absorb light within the red to near-infrared region of the visible spectrum. Initially achieving consistent device efficiencies above 1% clarified if any observed increase or decrease in device efficiency had arisen as a result of co-sensitisation with a dye.
A set manufacturing method for CH3NH3PbBr3 devices was established with average devices efficiencies consistently achieving 3 - 4% when prepared ambiently.
Following the investigation of several different routes of introducing the sensitising dye into the photovoltaic device, a set method for the co-sensitisation of CH3NH3PbBr3 devices was then developed which did not cause degradation of the perovskite active layer during the co-sensitisation process. The semi-transparent light orange colour of CH3NH3PbBr3 showed an evident colour change following co-sensitisation with a dye solution producing green and orange/red devices.
Photovoltaic testing of co-sensitised devices then revealed co-sensitised devices demonstrated improved performance in comparison to control devices. This method was then extended to CH3NH3PbI3 devices where it was found device performance could be improved with co-sensitisation for thicker devices which incorporated more of the sensitizing dye.
A paper has been published from these results highlighting the improvement of both the aesthetics and performance of perovskite photovoltaic devices through co-sensitisation with an organic dye.
Currently, a second paper is being drafted which investigates the relative changes to performance which are observed when varying the amount of dye within the perovskite device.
Exploitation Route We have demonstrated the capabilities of introducing organic dyes into perovskite solar cells through co-sensitisation of the perovskite active layer. We have shown the dye is actively contributing to the light harvesting and ultimately improving device performance.
The semi-transparent light orange colour of the methylammonium lead bromide perovskite films undergoes an evident colour change following co-sensitisation in the dye solution producing green and orange/red devices. This highlights the potential for tuning the colour of perovskite solar cells yielding aesthetically attractive devices which could be advantageous for applications as building integrated photovoltaics, product-integrated photovoltaics or in tandem devices.
Sectors Energy,Environment

URL https://pubs.rsc.org/en/content/articlehtml/2019/cc/c8cc07298a