Efficient organic-inorganic hybrid cathode interfacial layer enabled by polymeric dopant and its application in large-area polymer solar cells

An organic-inorganic hybrid cathode interfacial layer(CIL) was developed by doping ZnO with the naphthalene-diimide based derivative NDI-PFNBr. It was found the resulting organic-inorganic hybrid CIL showed apparently improved conductivity and could act as an effective cathode interlayer to modify indium tin oxide(ITO) transparent electrodes. As a result, by employing the blend of PTB7-Th:PC71BM as the photoactive layer, the inverted polymer solar cells(PSCs) exhibited a remarkable enhancement of power conversion efficiency(PCE) from 8.52% for the control device to 10.04% for the device fabricated with the hybrid CIL. Moreover, all device parameters were simultaneously improved by using this hybrid CIL. The improved open-circuit voltage(VOC) was attributed to the reduced work function of the ITO cathode, whereas the enhancements in fill factor(FF) and short-circuit current density(JSC) were assigned to the increased conductivity and more effective charge extraction and collection at interface. Encouragingly, when the thickness of the hybrid CIL was increased to 80 nm, the resulting device could still keep a PCE of 8.81%, exhibiting less thickness dependence. Considering these advantages, 16 and 93 cm2large-area PSCs modules were successfully fabricated from the hybrid CIL by using doctor-blade coating techniques and yielded a remarkable PCE of8.05% and 4.49%, respectively. These results indicated that the hybrid CIL could be a promising candidate to serve as the cathode interlayer for high-performance large-area inverted PSCs.

n-Type Conjugated Polymer Based on Dicyanodistyrylbenzene and Naphthalene Diimide Units for All-Polymer Solar Cells

All polymer solar cells （all-PSCs）, possessing superior mechanical strength and flexibility, offer the commercialization opportunity of the PSCs for flexible and portable devices. In this work, we designed and synthesized two copolymer acceptors based on dicyanodistyrylbenzene （DCB） and naph-thalene diimide （NDI） units. The corresponding copolymer acceptors are denoted as PDCB-NDI812 and PDCB-NDI1014. The medium band gap copolymer PBDB-T was selected as donor material for investigation of the photovoltaic performance. Two alI-PSCs devices showed power conversion efficiencies （PCE） of 4.26% and 3.43% for PDCB-NDI812 and PDCB-NDI1014, respectively. The improved PCE was ascribed to the higher short-circuit current （Jsc）, greater charge carrier mobility and higher exciton dissociation probability of the PBDB-T：PDCB-NDI812 blend film. These results suggest that DCB unit and NDI unit based copolymer acceptors are promising candidates for high performance alI-PSCs.