Advanced Energy Materials

Swapping main-chain substituents in a set of analogous wide-bandgap polymer donors is shown to result in gradual bulk-heterojunction (BHJ) device performance improvements when the polymers are combined with the nonfullerene acceptor “ITIC”. The gradual improvements result from better charge generation, collection, and reduced geminate and bimolecular recombination, leading to polymer-nonfullerene BHJ solar cells with power conversion efficiencies as high as 9.8%.

The photophysical properties of the electronically excited states of molecular aggregates are dictated by the mutual interactions of their building blocks and lead commonly to the formation of delocalized exciton states. After summarizing the theoretical background a survey of experiments on various material systems ranging from natural photosynthetic assemblies to self assembled artificial dye arrangements is provided.

A bifunctional NiFe-layered double hydroxide (LDH)/Co,N-carbon nanoframe (CNF) electrocatalyst, comprising 3–5 nm NiFe-LDH particles immobilized on Co,N-doped carbon nanoframes (Co,N-CNF), demonstrates excellent activities for both oxygen evolution reaction and oxygen reduction reaction, and outstanding performance and stability as cathode catalysts in rechargeable zinc–air batteries. Intimate contact between NiFe-LDH and Co,N-CNF preventing NiFe-LDH aggregation is the key to the higher electrocatalytic activity and stability of NiFe-LDH/Co,N-CNF compared to precious metal-based catalysts.

Over 11% efficiency random polymer-based nonfullerene solar cell is realized on the donor family of PTPTI-Tx containing various thiophene/bithiophene ratios in the backbone. A small-scale phase separation with an increased fraction of face-on oriented crystallites observed in the PTPTI-T70:m-ITIC blend enables efficient exciton dissociation and charge transport, thereby inducing a remarkably enhanced J_SC of 17.12 mA cm⁻² through this system.

Ternary solar cells with minimum voltage losses around 0.25 eV are designed by combining two donor polymers with same bulk and interface energy which make the hole transportation like in one donor polymer. The voltage losses were minimized due to E_ICT+ ≈ E_ICT−, where the trade-off between enhancing of charge generation and charge recombination by ICT states arrives at sweet spot.