Molecular Lock Induced by Chloroplatinic Acid Doping of PEDOT:PSS for High-Performance Organic Photovoltaics.

In organic photovoltaics (OPVs), the mechanical contact between charge transport layers and photoactive layer can influence the electrical contact that facilitates carrier collection. Unfortunately, the mechanical contact at the interface is rarely discussed in the OPV context. Herein, we report a distinct molecular locking effect that occurs between the donor molecules in the photoactive layer and the hole transport layer (HTL). This is achieved by doping chloroplatinic acid into poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate). The "molecular lock" at the interface leads to denser distribution and more ordered assembling of PM6 donor molecules close to the HTL. Consequently, the trap-assisted recombination in the cell is greatly suppressed, and the carrier lifetime is prolonged by more than 2 times. Together with the elevated charge carrier collection probability, a high fill factor of 77% and a power conversion efficiency of 16.5% are achieved in the PM6:Y6-based OPVs. This study provides a feasible way to boost the device performance by reinforcing the interfacial interaction between the HTL and photoactive layer.