A dopant–free polymeric hole transport material (HTM), RCP, based on benzo[1,2-b:4,5:b′]dithiophene and 2,1,3-benzothiadiazole exhibited a high efficiency of 17.3% in a perovskite solar cell and maintained its initial efficiency for over 1400 hours.

In this work, the impact of temperature-dependent aggregation behaviors in benzodithiophene (BDT)-based polymer donors (P D s) on the electrical, morphological, and photovoltaic performances of all-polymer solar cells (all-PSCs) is investigated. Two P D s, PBDB-T and PBDB-Bz, with thienyl or benzothienyl side chains and identical backbones are prepared. In contrast to PBDB-T, PBDB-Bz with bulkier side chains exhibits strong aggregation behavior in solution independent of temperatures between 20 and 100 °C. Notably, PBDB-Bz-based all-PSCs show a power conversion efficiency (PCE) of over 9% without any solvent additives (SAs) or thermal annealing (TA), whereas these treatments are inevitable in optimizing the PCE of PBDB-T-based all-PSCs. Furthermore, high PCEs for the PBDB-Bz-based devices are maintained, irrespective of their processing temperature (T proc ). However, the PCEs of PBDB-T-based devices are strongly dependent on their SA, TA, and T proc conditions. This phenomenon is due to the robust nature of the domain crystallinity and blend morphology of PBDB-Bz blends at different T proc s, resulting in T proc -tolerant charge mobilities and PCE values. Thus, the development of P D s with temperature-insensitive, strong aggregation behavior is crucial in producing reproducible, T proc -tolerant, and additive-free high-performance all-PSC devices.

Condensation copolymerization reactions of carbazole 3,6-diboronate with 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole (DTBT) only produce low-molecular-weight donor (D)-p-acceptor (A) copolymers. High-molecular-weight copolymers for use in optoelectronic devices are necessary for achieving extended p-conjugation and for controlling the copolymer processibility. To elucidate the cause of the persistently low molecular weight, we synthesized three 3,6-carbazole-based D-A copolymers using copolymerizations of N-9 0heptadecanyl-3,6-carbazole with DTBT, N-9 0 {2-[2-(2-methoxyethoxy)-ethoxy]-ethyl}-3,-6-carbazole with DTBT, and N-9 0 -heptadecanyl-3,6-carbazole with alkyl-substituted DTBT. We investigated several parameters for their influence on molecular copolymer weight, including the conformation of the chain during growth, the solubility of the monomers, and the dihedral angles between the donor and acceptor units. Size exclusion chromatography, UV-vis absorption spectroscopy, and computational studies revealed that the low molecular weights

Interlayers in organic solar cells (OSCs) play a crucial role in determining their charge extraction properties, device performance, and stability. In this work, two naphthalene diimide (NDI)-based n-type polymers (P(NDIDEG-T) and P(NDITEG-T)) incorporating oligo(ethylene glycol) (OEG) side chains of different lengths are designed and used as new electron transport layers (ETLs) in OSCs. The hydrophilic OEG side chains enable the processing of these n-type polymers using eco-friendly water/ethanol mixtures. In addition, the polar OEG groups effectively modify the work function of the Ag cathode, enabling the polymers to function as efficient ETLs. Consequently, when these OEG-based ETLs are applied to PM6:Y6-based OSCs, a maximum power conversion efficiency (PCE) of 15.43% is achieved, which is substantially higher than that of a reference OSC without an ETL (9.93%) and comparable to that of an OSC with a representative high-performance PFN-Br ETL (15.34%). We demonstrate that the P(NDIDEG-T)-based OSCs show both enhanced PCEs and better reproducibility than their P(NDITEG-T)-based counterparts, which are attributed to the lower surface tension and improved film uniformity of the P(NDIDEG-T) ETL. Also, the P(NDIDEG-T) ETL realizes OSCs with higher storage stability and more thickness-tolerant performance compared to the P(NDITEG-T) and PFN-Br ETLs. Our study provides useful guidelines for the design of ETLs suitable for the fabrication of highperformance, reproducible, and stable OSCs.

Our work presents a strategy for the development of eco-compatible highly efficient organic solar cells with sufficient solubility and optimized aggregation by introducing an ester-substituted thiophene.