The role of quantum dots in the functional layers of thin film polymer solar cells.

Abstract

Polymer solar cells (PSCs) have emerged as a promising class of photovoltaic technology, valued for their lightweight, flexibility, and potential for cost-effective, large-scale production. The ability to fully harness their potential is dependent on resolving the challenges mitigating their efficient power conversion efficiency (PCE) and environmental stability. As such, various advancements in material engineering have been embarked upon for device optimisation. This study explored the use of compound semiconductor quantum dots (SQDs), as guests in the functional layers of polymer solar cells using both conventional and inverted device architectures. Semiconductor quantum dots represent a class of inorganic materials that have been utilised for matured but expensive organic solar cells not viable for large-scale production. The fascinating inherent features of SQDs are leveraged in their careful introduction into the hole transport, photoactive, and electron transport layers of organic solar cells. The fullerene-based solar cells were fabricated upon the introduction of alloyed, core, and core-shell SQDs in their functional layers in ambient conditions. The II-VI compound SQDs are employed, such as CdTeSe, core ZnS, and core-shell CdxS/Zn1-xS. The photoactive layer blends are composed of poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) and poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b]dithiophene-2,6-diyl][3-fluoro- 2-[(2 ethylhexyl)-carbo-nyl]-thieno[3,4-b] thiophenediyl]]:[6,6]-phenyl C71 butyric acid methyl ester (PTB7:PC71BM). The as-synthesised SQDs and fabricated devices were subjected to various characterisations. The analysed data collected from various characterisation techniques showed that the incorporation of SQDs in the functional layers broadened the absorption range, improved light harvesting, and enhanced charge transport. These effects translated into better device parameters, as evident in the improved power conversion efficiencies of the modified devices. Ultimately, it can be inferred from this study that the use of semiconductor quantum dots in the various functional layers of PSCs at certain thresholds assisted in the optimisation of the devices, improving their PCE and shelf lives. This study explores the synergy between organic and inorganic materials (hybrid materials) that have positively impacted the performance of various PV technologies.