Increased open-circuit voltage of ZnO nanowire/PbS quantum dot bulk heterojunction solar cells with solution-deposited Mg(OH)2 interlayer

An ultrathin Mg(OH)2 layer was solution‐deposited onto the ZnO nanowires to solve the problem of interfacial charge recombination, caused by the increase of interfacial area in bulk heterojunction (BHJ) PbS colloidal quantum dot solar cells (CQDSCs). This Mg(OH)2 interlayer efficiently passivated the surface defects of ZnO nanowires and provided tunnel barrier at ZnO/PbS interface. As a result, the charge recombination at ZnO/PbS interface was largely suppressed, proved by the significantly elongated electron lifetime and the increased open‐circuit voltage of the Mg(OH)2‐involved BHJ CQDSCs. Careful thickness optimization of Mg(OH)2 interlayer finally brought a ∼33% increase in Voc and ∼25% improvement in power conversion efficiency. An ultrathin Mg(OH)2 interlayer was successfully solution‐deposited at the heterojunction of ZnO nanowire/PbS quantum dot solar cells to passivate surface defects of ZnO and provide a tunnel barrier for the interface charge recombination, which is proved to dramatically improve Voc by 33% and PCE by 25%.