Deep level transient Fourier spectroscopy （DLTFS） measurements are used to characterize the deep impurity levels in n-type 4H-SiC by vanadium ions implantation. Two acceptor levels of vanadium at Ec - 0.81 and Ec - ...Deep level transient Fourier spectroscopy （DLTFS） measurements are used to characterize the deep impurity levels in n-type 4H-SiC by vanadium ions implantation. Two acceptor levels of vanadium at Ec - 0.81 and Ec - 1.02eV with the electron capture cross section of 7.0 × 10^16 and 6.0 × 10^-16 cm^2 are observed, respectively. Low-temperature photoluminescence measurements in the range of 1.4-3.4eV are also performed on the sample, which reveals the formation of two electron traps at 0.80 and 1. 16eV below the conduction band. These traps indicate that vanadium doping leads to the formation of two deep acceptor levels in 4H-SiC,with the location of 0.8±0.01 and 1. 1 ±0.08eV below the conduction band.展开更多
Fully conjugated donor-acceptor （D-A） block copolymers, P3HT-b-PNDIT, containing p-type poly（3-hexylthio- phene） （P3HT） and n-type poly（naphthalene bismide） （PNDIT） segments are synthesized in a one-pot reac...Fully conjugated donor-acceptor （D-A） block copolymers, P3HT-b-PNDIT, containing p-type poly（3-hexylthio- phene） （P3HT） and n-type poly（naphthalene bismide） （PNDIT） segments are synthesized in a one-pot reaction via Stille coupling polycondensation. Various D-A block copolymers with low polydispersities （1.42--1.56） are ob- tained through further separation via preparative GPC. The structural and molecular features of block copolymers are verified by 1H NMR, FTIR spectra, UV-Vis absorption, differential scanning calorimetry （DSC） and cyclic voltammetry （CV）. It is found that optical and electrochemical properties of D-A block copolymers are strongly de- pendent on the combination ratio of the donor P3HT and acceptor PNDIT segment. By reducing the acceptor block lengths, the highest occupied molecular orbital （HOMO） energy levels of D-A block copolymers sequentially rise, leading to the sequential decrease of energy gaps. To the best of our knowledge, this is the first report on engineer- ing the energy levels of fully conjugated D-A block copolymers by tuning donor and acceptor chain lengths. More- over, compared to D/A polymer blends, the all-conjugated D-A block copolymer films show significant fine struc- tures and much smoother film morphologies.展开更多
To achieve high-efficiency polymer solar cells(PSCs),it is not only important to develop high-performance small molecule acceptors(SMAs)but also to find a matching polymer donor to achieve optimal morphology and match...To achieve high-efficiency polymer solar cells(PSCs),it is not only important to develop high-performance small molecule acceptors(SMAs)but also to find a matching polymer donor to achieve optimal morphology and matching electronic properties.Currently,state-of-the-art SMAs mostly rely on a donor polymer named PM6.However,as the family of SMAs continues to expend,PM6 may not be the perfect polymer donor due to the requirement of energy level matching.In this work,we tune the energy level of PM6 via the strategy of ternary copolymerization.We achieve two donor polymers(named PL-1 and PL-2)with upshifted HOMO(the highest occupied molecular orbital)energy level(compared with PM6),and can thus match with the SMAs with upshifted HOMO energy levels compared with Y6.These two copolymers exhibit slightly higher order of molecular packing and similar charge transport properties,which demonstrate that the method of ternary copolymerization can fine tune the HOMO level of donor polymers,while the morphology and mobility of the blend film remain mostly unaffected.Among them,the best device based on PL-1:Y6 exhibits power conversion efficiencies(PCEs)of 16.37%with lower open circuit voltage(Voc)but higher short circuit current voltage(Jsc)and fill factor(FF)than that of the device based on PM6:Y6.This work provides an effective approach to find polymer matches for the SMAs with upshifted HOMO levels.展开更多
文摘Deep level transient Fourier spectroscopy （DLTFS） measurements are used to characterize the deep impurity levels in n-type 4H-SiC by vanadium ions implantation. Two acceptor levels of vanadium at Ec - 0.81 and Ec - 1.02eV with the electron capture cross section of 7.0 × 10^16 and 6.0 × 10^-16 cm^2 are observed, respectively. Low-temperature photoluminescence measurements in the range of 1.4-3.4eV are also performed on the sample, which reveals the formation of two electron traps at 0.80 and 1. 16eV below the conduction band. These traps indicate that vanadium doping leads to the formation of two deep acceptor levels in 4H-SiC,with the location of 0.8±0.01 and 1. 1 ±0.08eV below the conduction band.
文摘Fully conjugated donor-acceptor （D-A） block copolymers, P3HT-b-PNDIT, containing p-type poly（3-hexylthio- phene） （P3HT） and n-type poly（naphthalene bismide） （PNDIT） segments are synthesized in a one-pot reaction via Stille coupling polycondensation. Various D-A block copolymers with low polydispersities （1.42--1.56） are ob- tained through further separation via preparative GPC. The structural and molecular features of block copolymers are verified by 1H NMR, FTIR spectra, UV-Vis absorption, differential scanning calorimetry （DSC） and cyclic voltammetry （CV）. It is found that optical and electrochemical properties of D-A block copolymers are strongly de- pendent on the combination ratio of the donor P3HT and acceptor PNDIT segment. By reducing the acceptor block lengths, the highest occupied molecular orbital （HOMO） energy levels of D-A block copolymers sequentially rise, leading to the sequential decrease of energy gaps. To the best of our knowledge, this is the first report on engineer- ing the energy levels of fully conjugated D-A block copolymers by tuning donor and acceptor chain lengths. More- over, compared to D/A polymer blends, the all-conjugated D-A block copolymer films show significant fine struc- tures and much smoother film morphologies.
基金the Shenzhen Technology and Innovation Commission(JCYJ20170413173814007,JCYJ20170818113905024)the Hong Kong Research Grants Council(Research Impact Fund R6021-18)(16305915,16322416,606012,16303917)+1 种基金Hong Kong Innovation and Technology Commission(ITCCNERC14SC01,ITS/471/18)the National Natural Science Foundation of China(51573120,51973146,51820105003)。
文摘To achieve high-efficiency polymer solar cells(PSCs),it is not only important to develop high-performance small molecule acceptors(SMAs)but also to find a matching polymer donor to achieve optimal morphology and matching electronic properties.Currently,state-of-the-art SMAs mostly rely on a donor polymer named PM6.However,as the family of SMAs continues to expend,PM6 may not be the perfect polymer donor due to the requirement of energy level matching.In this work,we tune the energy level of PM6 via the strategy of ternary copolymerization.We achieve two donor polymers(named PL-1 and PL-2)with upshifted HOMO(the highest occupied molecular orbital)energy level(compared with PM6),and can thus match with the SMAs with upshifted HOMO energy levels compared with Y6.These two copolymers exhibit slightly higher order of molecular packing and similar charge transport properties,which demonstrate that the method of ternary copolymerization can fine tune the HOMO level of donor polymers,while the morphology and mobility of the blend film remain mostly unaffected.Among them,the best device based on PL-1:Y6 exhibits power conversion efficiencies(PCEs)of 16.37%with lower open circuit voltage(Voc)but higher short circuit current voltage(Jsc)and fill factor(FF)than that of the device based on PM6:Y6.This work provides an effective approach to find polymer matches for the SMAs with upshifted HOMO levels.
