Enhanced photocurrent in PbSe nanorod-quantum dot bulk nano-heterojunction solar cells

Owing to their remarkable multiple exciton generation (MEG) yield, PbSe nanorods (NRs) have been considered as one of the most promising materials to overcome the Shockley–Queisser limit. Unfortunately, assessing the direct role of the PbSe NRs in solar cell designs has been challenging due to their unoptimized film microstructure and poor performances. Here we devise a cell architecture that overcomes these limitations by inserting an electron blocking quantum dot (QD) layer to the NR/metal interface. Further enhancement was achieved by creating a bulk nano-heterojunction (BNHJ) platform comprising the covalently bonded PbSe NRs-donors and PbSe QDs-acceptors. The overall benefit of the exciton cascade, enabling an efficient non-radiative energy transfer, was evidenced through a photocurrent enhancement at energies where the hot exciton generation is expected to take place, that is ≥ 2 E g ( E g = band gap). Resulting BNHJ solar cells exhibit 2.42% efficiency and a peak internal quantum efficiency of 100% with a threshold photon energy of 2.9 E g , outperforming the present cells comprising the NRs with similar band gaps. This proof-of-principle demonstrates that the concept of BNHJ has a practical potential and a breakthrough in the design of the MEG-based solar cells.