Band gap tunable quaternary PbxCd1−xS1−ySey quantum dot-sensitized solar cells with an efficiency of 9.24% under 1% sun. Issue 11 (16th May 2022) - Boon-on, Patsorn
Abstract : We present a new solar absorber material – quaternary Pb x Cd1− x S1− y Se y quantum dots (QDs) – with a band gap E g tunable over a broad range of 1.5–2.4 eV. Abstract : We present a new solar absorber material – quaternary Pb x Cd1− x S1− y Se y quantum dots (QDs) – with a band gap E g tunable over a broad range of 1.5–2.4 eV. Pb x Cd1− x S1− y Se y QDs were prepared using a two-step cation/anion co-alloying approach: first, Pb 2+ was incorporated into the binary CdS host by cation exchange, leading to ternary Pb x Cd1− x S QDs. Second, Se 2− replaced a fraction of S 2− in Pb x Cd1− x S by anion exchange, leading to quaternary Pb x Cd1− x S1− y Se y QDs. The reactions reduced the E g from 2.42 (CdS, absorption onset 500 nm) to 1.91 (Pb x Cd1− x S, 650 nm) to 1.55 eV (Pb x Cd1− x S1− y Se y, 800 nm). The E g of Pb x Cd1− x S1− y Se y (1.55 eV) is close to the Shockley–Queisser gap. Solid-state Pb x Cd1− x S1− y Se y QD solar cells (QDSCs) were fabricated with Spiro-OMeTAD as the hole transport material. The best cell (Pb0.15 Cd0.85 S0.75 Se0.18 ) yielded J sc = 13.71 mA cm −2, V oc = 0.59 V, FF = 54.8% and PCE = 4.43% under 1 sun. At low light intensities, the PCE increased to 7.18% under 10% sun and further to 9.24% under 1% sun. The co-alloying treatment improved the PCE from 4.49 (CdS) to 8.48 (Pb x Cd1− x S) to 9.24% (Pb0.15 Cd0.85 S0.75 Se0.18 ) under 1% sun. The cell with a PCE of 9.24% can be categorized as a high-efficiency QDSC, suggesting that Pb x Cd1− x S1− y Se y can be an efficient solar absorber.