Proceedings of Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP20)
DOI: https://doi.org/10.29363/nanoge.iperop.2020.051
Publication date: 14th October 2019
Recent reports on dye-sensitized solar cells (DSSCs) under ambient light conditions [1][2] have reopened the path towards widespread indoor photovoltaics. DSSCs possess promising features such as solution-based fabrication, low-toxicity, colour-tunability and light-weight. However, challenges remain including the appropriate choice of the electrolyte or solid hole conductor. A 2015 report by Freitag et al.[3] proposes the use of a copper phenanthroline electrolyte towards the development of efficient liquid- and solid-state DSSCs. Their solid-state DSSCs are obtained by slow evaporation of the electrolyte in liquid-state cells.
Originating from the above work, we have studied the co-sensitization effect of two organic dyes in a copper bipyridyl electrolyte system.[4] A high-performing costly dye (XY1)[5] was co-adsorbed with a moderately-performing cheaper dye (5T)[6] to achieve similar (9.5% at 1 sun) or superior (10.2% at 0.1 sun) performance to the XY1 dye alone. This translates to a 1.4-fold increase in cost performance of the sensitizer. Photophysical measurements suggested that the co-sensitized devices (XY1+5T) have better dye coverage and exhibit longer electron lifetimes especially at lower light intensities. Further testing of XY1+5T under indoor fluorescent lighting revealed a power conversion efficiency (PCE) of 29% at 1000 lux, which is among the highest reported under similar conditions. We believe our findings revalue the co-sensitization method as a cost-reduction strategy for DSSCs. Proposals towards more practical DSSCs (e.g. solid-state) will also be discussed during the talk.
E.T. thanks the Energy Technology Partnership for their research funding and the Japan Student Services Organization for their PhD studentship.