Lead antimony sulfide (Pb5Sb8S17) solid-state quantum dot-sensitized solar cells with an efficiency of over 4%

• First demonstration of solid-state Pb5Sb8S17 quantum dot-sensitized solar cells.
• The best cell achieved a respectable efficiency of 4.14% and a normalized Jsc of 20.0 mA cm−2 under 10% sun.
• The best efficiency is 65% higher than the best previous result.
• Pb5Sb8S17 has a large optical absorption coefficient and a near optimal Eg.
• External quantum efficiency (EQE) spectral range: 300–800 nm; maximal EQE = 65% at λ = 450 nm.

Lead antimony sulfides are rare in nature and relatively unexplored ternary semiconductors. This work investigates the photovoltaic performance of Pb–Sb–S quantum dot-sensitized solar cells (QDSCs). Pb5Sb8S17 nanoparticles are grown on mesoporous TiO2 electrodes using the successive ionic layer adsorption reaction process. The synthesized Pb5Sb8S17 nanoparticles exhibit two attractive features for a good solar absorber material: a high optical absorption coefficient and a near optimal energy gap. Solid-state QDSCs are fabricated from the synthesized Pb5Sb8S17 nanoparticles using Spiro-OMeTAD as the hole-transporting material. The best cell yields a short-circuit current density Jsc of 11.92 mA cm−2, an open-circuit voltage Voc of 0.48 V, a fill factor FF of 30.7% and a power conversion efficiency (PCE) of 1.76% under 1sun. The external quantum efficiency (EQE) spectrum covers a spectral range of 350–800 nm with a maximal EQE = 65% at λ = 450 nm. At the reduced light intensity of 10% sun, the PCE increases to 4.14% with Jsc = 2.0 mA cm−2 (which could be normalized to 20 mA cm−2 under 1 sun). This PCE is 65% higher than the best previous result. The respectable PCE and Jsc indicate that Pb5Sb8S17 could be a potential candidate for a solar absorber material.