14.46% Efficiency small molecule organic photovoltaics enabled by the well trade-off between phase separation and photon harvesting

Small molecule organic photovoltaics(SMPVs) were prepared by utilizing liquid crystalline donor material BTR-Cl and two similar optical bandgap non-fullerene acceptor materials BTP-BO-4 F and Y6.The BTPBO-4 F and Y6 have the similar optical bandgap and different absorption coefficients.The corresponding binary SMPVs exhibit different short circuit current density(/sc)(20.38 vs.23.24 mA cm^(-2)),and fill factor(FF)(70.77% vs.67.21%).A 14.46% power conversion efficiency(PCE) is acquired in ternary SMPVs with 30 wt% Y6,companied with a JSC of 24.17 mA cm^(-2) a FF of 68.78% and an open circuit voltage(Voc) of 0.87 V.The improvement on PCE of ternary SMPVs should originate from the well trade-off between phase separation and photon harvesting of ternary active layers by incorporating 30 wt% Y6 in acceptors.This work may deliver insight onto the improved performance of SMPVs by superposing the superiorities of binary SMPVs with similar optical bandgap acceptors into one ternary cell.

Annealing-free alcohol-processable MoO_(X) anode interlayer enables efficient light utilization in organic photovoltaics

Molybdenum oxide(MoO_(x))is a commonly used hole extraction material in organic photovoltaics.The MoO_(x) interlayer is deposited typically via thermal evaporation in vacuum.To meet the need for rollto-roll manufacturing,solution processing of MoO_(x) without post-annealing treatment is essential.Herein,we demonstrate an effective approach to produce annealing-free,alcohol-processable MoO_(x) anode interlayers,namely S-MoO_(x),by utilizing the bis(catecholato)diboron(B_(2) Cat_(2))molecule to modify the surface oxygen sites in MoO_(x).The formation of surface diboron-oxygen complex enables the alcohol solubility of S-MoO_(x).An enhanced light utilization is realized in the S-MoO_(x)-based organic photovoltaics.This affords a superior short-circuit current density(Jsc)close to 26 mA cm^(-2) and ultimately a high power-conversion efficiency(PCE)of 15.2%in the representative PM6:Y6 based inverted OPVs,which is one of the highest values in the inverted OPVs using an as-cast S-MoO_(x) anode interlayer.

Small molecule donors with different conjugated π linking bridges: Synthesis and photovoltaic properties

Three small molecule(SM)donors,namely B-T-CN,B-TT-CN and B-DTT-CN,with differentπconjugated bridges were synthesized in this research.Interestingly,with the conjugated fused rings of theπlinking bridge increasing,the SM HOMO levels exhibit a decline tendency with–5.27 eV for B-T-CN,–5.31 eV for B-TT-CN and–5.40 eV for B-DTT-CN.After blending the SM donors with the fullerene acceptor PC71BM,the all SM organic solar cells(OSCs)achieved high Vocs of 0.90 to 0.96 V.However,the phase separation morphology and molecule stacking are also unexpectedly changed together with the enhancement of conjugated degree ofπbridges,resulting in a lower power conversion efficiency(PCE)for the B-DTT-CN:PC71BM device.Our results demonstrate and provide a useful way to enhance OSC Voc and the morphology needs to be further optimized.

Block copolymers as efficient cathode interlayer materials for organic solar cells

Emerging needs for the large-scale industrialization of organic solar cells require high performance cathode interlayers to facilitate the charge extraction from organic semiconductors.In addition to improving the efficiency,stability and processability issues are major challenges.Herein,we design block copolymers with well controlled chemical composition and molecular weight for cathode interlayer applications.The block copolymer coated cathodes display high optical transmittance and low work function.Conductivity studies reveal that the block copolymer thin film has abundant conductive channels and excellent longitudinal electron conductivity due to the interpenetrating networks formed by the polymer blocks.Applications of the cathode interlayers in organic solar cells provide higher power conversion efficiency and better stability compared to the most widelyapplied ZnO counterparts.Furthermore,no post-treatment is needed which enables excellent processability of the block copolymer based cathode interlayer.