Efficient counter electrode for quantum dot sensitized solar cells using p-type PbS@reduced graphene oxide composite

Abstract

This study developed a novel PbS-rGO composite counter electrode to enhance the performance of quantum dot-sensitized solar cells (QDSSCs). The composite was synthesized via a hydrothermal method by anchoring PbS nanocubes onto reduced graphene oxide (rGO) sheets. The effect of the mass ratio of rGO to PbS (0.0, 0.1, 0.3, and 0.6) on power conversion efficiency (PCE) was investigated. The optimized rGO-PbS (0.03) composite achieved a power conversion efficiency of 5.358%, V _oc of 0.540 V, J _sc of 21.157 mA cm^-2, and FF of 0.516. The rGO framework provides an interconnected conductive network that facilitates efficient charge transport, reduces charge transfer resistance, and improves overall conductivity. Electrochemical analyses confirmed the superior electrocatalytic activity of the composite in reducing the S _n ^2-/S^2- redox couple. The unique band alignment between rGO and PbS optimized the electron transfer pathways. The hierarchical structure increased the surface area and light absorption, enabling a more effective charge transfer at the electrode-electrolyte interface.

Scheme 1. Synthesis of the FTO/PbS–rGO counter electrode.

Fig. 1. XRD patterns of rGO, PbS, rGO–PbS x (x = 0.01, 0.03, 0.06) nanocomposites.

Fig. 2. (a) Raman spectrum of PbS, GO, rGO, and rGO–PbS (x) (x = 0.01, 0.03, 0.06) nanocomposites; (b) inset Raman spectrum in range 2500–2800 cm⁻¹.

Fig. 3. FT-IR of PbS, GO, rGO, and rGO–PbS (x) (x = 0.01, 0.03, 0.06) nanocomposites.

Fig. 4. FESEM images of (a) PbS, and (b–d) rGO–PbS (x) (x = 0.01, 0.03, 0.06) nanocomposites.

Fig. 5. (a) EDX mapping and (b) EDX spectrum of rGO–PbS (0.03) nanocomposites CE.

Fig. 6. (a and b) TEM and (c and d) HrTEM of rGO–PbS (0.03) nanocomposites CE.

Fig. 7. High-resolution XPS (a) C 1s spectra of GO (b) C 1s (c) Pb 4f, (d) S 2p, and spectrum of rGO–PbS (0.03) nanocomposites CE.

Fig. 8. (a) J–V curves; (b) CV plots; (c) Nyquist plots (inset: the equivalent circuit), and (d) Tafel polarization of PbS, GO, rGO, and rGO–PbS (x) (x = 0.01, 0.03, 0.06) electrode.

Fig. 9. Schematic structure of the QDSSC devices.