Surface and interfacial engineering for aqueous-processed quantum dots-sensitized solar cell with efficiency approaching 11 %

This study presents a straightforward method for the aqueous synthesis of CuInSe2 (CISe) quantum dots (QDs) utilizing various surface linkers. The energy band position and average photoluminescent lifetime of QDs are both influenced by different surface linkers. As a result, L-cysteine-capped CISe (C-CISe) quantum-dot sensitized solar cell (QDSSC) achieves an exceptional efficiency of 9.06 %, signifying a substantial improvement of approximately 39.0 % in comparison to QDSSC sensitized with thioglycolic acid-capped CISe QDs. After refining the device efficiency by modulating surface linkers of pre-synthesized QDs, surface and interface modification, which involved CuInS2 (CIS) QDs and Gd3+ ions, respectively, were proposed to further improve the photovoltaic efficiency of pristine C-CISe cell. Implementing the cascade co-sensitization architecture of C-CISe and CIS QDs in the device resulted in an improved efficiency of 9.99 %, compared to devices that used an inverted cascaded CIS/ C-CISe structure, which obtained an efficiency of 7.20 %. Furthermore, the Gd3+ ions, possessing a stable halffilled electron configuration, are the first report employed for heterointerface modification between C-CISe and CIS QD in QDSSC. The resulting C-CISe/Gd/CIS cell achieved a JSC of 31.4 mA/cm2, VOC of 0.63 V, and FF of 55.2 %, resulting in the highest efficiency of 10.91 %. Electrochemical impedance spectroscopy, open-circuit voltage decay, and intensity-modulated photocurrent/voltage spectroscopy collectively indicate that the introduction of interface modification (Gd3+ ions) and surface co-sensitization (CIS QDs) can effectively reduce the quantity of charge recombination pathways at the interface between the electrolyte and photoanode.