Pb5Sb8S17 quantum dot‐sensitized solar cells with an efficiency of 6% under 0.05 sun: Theoretical and experimental studies

Pb5Sb8S17 has recently been demonstrated to be a potential solar absorber material having an efficiency of 4.14% under 0.1 sun. This work reports on the improved performance of solid‐state Pb5Sb8S17 quantum dot‐sensitized solar cells (QDSCs). Density functional calculations revealed indirect and direct energy gaps of 1.64 and 1.70 eV, respectively, large optical absorption coefficients approximately 105 cm−1 in the visible range, and a large static dielectric function (ε0 = 44) facilitating charge collection. Pb5Sb8S17 nanoparticles were synthesized using the successive ionic layer adsorption and reaction process. Solid‐state QDSCs were fabricated from the synthesized nanoparticles with spiro‐OMeTAD as the hole‐transporting material. The best cell yielded a short‐circuit current density Jsc of 11.88 mA/cm2, an open‐circuit voltage Voc of 0.48 V, a fill factor FF of 45.7%, and an efficiency η of 2.61% under 1 sun. The η increased to 5.13% at the reduced light of 0.1 sun and further increased to 6.04% at 0.05 sun with Jsc = 1.33 mA/cm2, Voc = 0.41 V, and FF = 55.7%. The present result represents a 24% improvement over the best previous result. This efficiency of approximately 6% can be categorized as one of the highest‐efficiency ternary QDSCs (except the widely studied Cu‐In‐Se system) and is comparable to the performance of other high‐efficiency QDSCs based on single‐layered semiconductor absorbers, suggesting that Pb5Sb8S17 could be an efficient absorber material for solar cells