In order to reduce deep level defects, the theory and process design of 4H-SiC homoepitaxial layer implanted by carbon ion are studied. With the Monte Carlo simulator TRIM, the ion implantation range, location of peak...In order to reduce deep level defects, the theory and process design of 4H-SiC homoepitaxial layer implanted by carbon ion are studied. With the Monte Carlo simulator TRIM, the ion implantation range, location of peak concentration and longitudinal straggling of carbon are calculated. The process for improving deep energy level in undoped 4H-SiC homoepitaxial layer by three times carbon ion-implantation is proposed, including implantation energy, dose, the SiO2 resist mask, annealing temperature, annealing time and annealing protection. The deep energy level in 4H-SiC material can be significantly improved by implantation of carbon atoms into a shallow surface layer. The damage of crystal lattice can be repaired well, and the carbon ions are effectively activated after 1 600 ℃ annealing, meanwhile, deep level defects are decreased.展开更多
Focusing on the low open circuit voltage(V_(OC))and fill factor(FF)in flexible Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)solar cells,indium(In)ions are introduced into the CZTSSe absorbers near Mo foils to modify the back interface...Focusing on the low open circuit voltage(V_(OC))and fill factor(FF)in flexible Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)solar cells,indium(In)ions are introduced into the CZTSSe absorbers near Mo foils to modify the back interface and passivate deep level defects in CZTSSe bulk concurrently for improving the performance of flexible device.The results show that In doping effectively inhibits the formation of secondary phase(Cu(S,Se)_(2))and VSndefects.Further studies demonstrate that the barrier height at the back interface is decreased and the deep level defects(Cu_(Sn)defects)in CZTSSe bulk are passivated.Moreover,the carrier concentration is increased and the V_(OC) deficit(V_(OC,def))is decreased significantly due to In doping.Finally,the flexible CZTSSe solar cell with 10.01%power conversion efficiency(PCE)has been obtained.The synergistic strategy of interface modification and bulk defects passivation through In incorporation provides a new thought for the fabrication of efficient flexible kesterite-based solar cells.展开更多
Fifty-millimeter undoped indium phosphide(InP)wafers polished on both sides were measured by a psdegenerate four-wave mixing(FWM)technique.Deep defect related carrier generation,recombination,and decay kinetics and ex...Fifty-millimeter undoped indium phosphide(InP)wafers polished on both sides were measured by a psdegenerate four-wave mixing(FWM)technique.Deep defect related carrier generation,recombination,and decay kinetics and exposure characteristics were measured by time-resolved picosecond FWM at 1064nm at room temperature.The diffraction efficiency of an undoped InP sample as a function of energy is shown for two grating periods.Deep donor defects in undoped InP samples are confirmed by the pronounced effect of space charge electric field on carrier transport.展开更多
Halide perovskite solar cells(PSCs)have already demonstrated power conversion efficiencies above 25%,which makes them one of the most attractive photovoltaic technologies.However,one of the main bottlenecks towards th...Halide perovskite solar cells(PSCs)have already demonstrated power conversion efficiencies above 25%,which makes them one of the most attractive photovoltaic technologies.However,one of the main bottlenecks towards their commercialization is their long-term stability,which should exceed the 20-year mark.Additive engineering is an effective pathway for the enhancement of device lifetime.Additives applied as organic or inorganic compounds,improve crystal grain growth enhancing power conversion efficiency.The interaction of their functional groups with the halide perovskite(HP)absorber,as well as with the transport layers,results in defect passivation and ion immobilization improving device performance and stability.In this review,we briefly summarize the different types of additives recently applied in PSC to enhance not only efficiency but also long-term stability.We discuss the different mechanism behind additive engineering and the role of the functional groups of these additives for defect passivation.Special emphasis is given to their effect on the stability of PSCs under environmental conditions such as humidity,atmosphere,light irradiation(UV,visible)or heat,taking into account the recently reported ISOS protocols.We also discuss the relation between deep-defect passivation,non-radiative recombination and device efficiency,as well as the possible relation between shallow-defect passivation,ion immobilization and device operational stability.Finally,insights into the challenge and criteria for additive selection are provided for the further stability enhancement of PSCs.展开更多
Unintentionally doped 4H-SiC homoepitaxial layers grown by hot-wall chemical vapor deposition （HWCVD） have been studied using photoluminescence （PL） technique in the temperature range of 10 to 240 K. A broadband g...Unintentionally doped 4H-SiC homoepitaxial layers grown by hot-wall chemical vapor deposition （HWCVD） have been studied using photoluminescence （PL） technique in the temperature range of 10 to 240 K. A broadband green luminescence has been observed. Vacancies of carbon （Vc） are revealed by electron spin resonance （ESR） technique at 110 K. The results strongly suggest that the green band luminescence, as shallow donor-deep accepter emission, is attributed to the vacancies of C and the extended defects. The broadband green luminescence spectrum can be fitted by the two Gauss-type spectra using nonlinear optimization technique. It shows that the broad-band green luminescence originates from the combination of two independent radiative transitions. The centers of two energy levels are located 2.378 and 2.130 eV below the conduction band, respectively, and the ends of two energy levels are expanded and superimposed each other.展开更多
All-inorganic perovskites are advantageous in terms of improved thermal stability compared to organic-inorganic counterparts.However,the ion migration-induced hysteresis significantly undermines the long-term operatio...All-inorganic perovskites are advantageous in terms of improved thermal stability compared to organic-inorganic counterparts.However,the ion migration-induced hysteresis significantly undermines the long-term operational stability of all-inorganic perovskite solar cells(PSCs),particularly in mixed halide perovskites.Herein,we report that tin-lead(Sn-Pb)alloying for all-inorganic mixed halide perovskites can effectively inhibit the ion migration behavior,as comprehensively revealed by the time-of-flight secondary ion mass spectrometry(TOF-SIMS),optical microscopy and galvanostatic measurements.On one hand,the small-sized Sn2+cations can tighten the lattice structure to enhance the Pb/Sn-X(X=I and Br)ionic bonds,thereby effectively immobilizing the halide ions.On the other hand,Sn substitution can significantly reduce anti-site defects,such as I_(Cs)and I_(Pb),which are considered potential pathways for ion migration.With these advantages,ion migration is greatly suppressed in Sn-Pb alloyed inorganic perovskites,resulting in reduced hysteresis and improved operational stability of PSC devices.展开更多
ZnSe nanoribbons were synthesized with chemical vapor deposition route. The excitation power-dependent photol and surface photovoltage （SPV） techniques were used to study the optoelectronic properties of the as-grow...ZnSe nanoribbons were synthesized with chemical vapor deposition route. The excitation power-dependent photol and surface photovoltage （SPV） techniques were used to study the optoelectronic properties of the as-grown ZnSe nanoribbons. Three deep defect （DD）-related emission bands, respectively, centered at 623 nm （DD1）, 563 nm （DD2） and 525 nm （DD3）, emerge orderly with increasing the excitation power, which is attributed to the saturation of the DD states from deeper to shallower level. The SPV spectrum and the corresponding phase spectrum show that DD1 mainly acts as recombination center, while DD2 and DD3 can act as both the recombination center and electron traps. The influence of the trapping electrons on the SPV response dynamic was studied with transient SPV.展开更多
基金Supported by the National Natural Science Foundation of China (No. 61006008)Xi'an Applied Materials Innovation Fund (No. XA-AM-200607)
文摘In order to reduce deep level defects, the theory and process design of 4H-SiC homoepitaxial layer implanted by carbon ion are studied. With the Monte Carlo simulator TRIM, the ion implantation range, location of peak concentration and longitudinal straggling of carbon are calculated. The process for improving deep energy level in undoped 4H-SiC homoepitaxial layer by three times carbon ion-implantation is proposed, including implantation energy, dose, the SiO2 resist mask, annealing temperature, annealing time and annealing protection. The deep energy level in 4H-SiC material can be significantly improved by implantation of carbon atoms into a shallow surface layer. The damage of crystal lattice can be repaired well, and the carbon ions are effectively activated after 1 600 ℃ annealing, meanwhile, deep level defects are decreased.
基金supported by the National Natural Science Foundation of China(62074037)the Science and Technology Department of Fujian Province(2020I0006)the Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(2021ZZ124)。
文摘Focusing on the low open circuit voltage(V_(OC))and fill factor(FF)in flexible Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)solar cells,indium(In)ions are introduced into the CZTSSe absorbers near Mo foils to modify the back interface and passivate deep level defects in CZTSSe bulk concurrently for improving the performance of flexible device.The results show that In doping effectively inhibits the formation of secondary phase(Cu(S,Se)_(2))and VSndefects.Further studies demonstrate that the barrier height at the back interface is decreased and the deep level defects(Cu_(Sn)defects)in CZTSSe bulk are passivated.Moreover,the carrier concentration is increased and the V_(OC) deficit(V_(OC,def))is decreased significantly due to In doping.Finally,the flexible CZTSSe solar cell with 10.01%power conversion efficiency(PCE)has been obtained.The synergistic strategy of interface modification and bulk defects passivation through In incorporation provides a new thought for the fabrication of efficient flexible kesterite-based solar cells.
文摘Fifty-millimeter undoped indium phosphide(InP)wafers polished on both sides were measured by a psdegenerate four-wave mixing(FWM)technique.Deep defect related carrier generation,recombination,and decay kinetics and exposure characteristics were measured by time-resolved picosecond FWM at 1064nm at room temperature.The diffraction efficiency of an undoped InP sample as a function of energy is shown for two grating periods.Deep donor defects in undoped InP samples are confirmed by the pronounced effect of space charge electric field on carrier transport.
基金the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grant SEV-2013-0295 for the postdoctoral contract to H.X.To the Solar Era.Net Cofund 2(EU)and the AEI(Spain)for the project Pr Oper Photo Mi Le(Ref 12 and PCI2020-112185)the Spanish State Research Agency for the grant Self-Power(PID2019-10^(4)272RB-C54/AEI/10.13039/501100011033)+2 种基金the Agència de Gestiód’Ajuts Universitaris i de Recerca(AGAUR)for the support to the consolidated Catalonia research group 217 SGR 329 and the Xarxa d’R+D+I Energy for Society(XRE4S)CONACYT for the scholarship to C.P.ICN2 is supported by the Severo Ochoa program from Spanish MINECO(Grant No.SEV-2017-0706)funded by the CERCA Programme/Generalitat de Catalunya。
文摘Halide perovskite solar cells(PSCs)have already demonstrated power conversion efficiencies above 25%,which makes them one of the most attractive photovoltaic technologies.However,one of the main bottlenecks towards their commercialization is their long-term stability,which should exceed the 20-year mark.Additive engineering is an effective pathway for the enhancement of device lifetime.Additives applied as organic or inorganic compounds,improve crystal grain growth enhancing power conversion efficiency.The interaction of their functional groups with the halide perovskite(HP)absorber,as well as with the transport layers,results in defect passivation and ion immobilization improving device performance and stability.In this review,we briefly summarize the different types of additives recently applied in PSC to enhance not only efficiency but also long-term stability.We discuss the different mechanism behind additive engineering and the role of the functional groups of these additives for defect passivation.Special emphasis is given to their effect on the stability of PSCs under environmental conditions such as humidity,atmosphere,light irradiation(UV,visible)or heat,taking into account the recently reported ISOS protocols.We also discuss the relation between deep-defect passivation,non-radiative recombination and device efficiency,as well as the possible relation between shallow-defect passivation,ion immobilization and device operational stability.Finally,insights into the challenge and criteria for additive selection are provided for the further stability enhancement of PSCs.
基金supported by the State Key Development Program for Basic Research of China (No. 51327020202)the Key Fund of the Ministryof Education of China (No. 106150)the Xi’an Applied Materials Innovation Fund (No. XA-AM-200607).
文摘Unintentionally doped 4H-SiC homoepitaxial layers grown by hot-wall chemical vapor deposition （HWCVD） have been studied using photoluminescence （PL） technique in the temperature range of 10 to 240 K. A broadband green luminescence has been observed. Vacancies of carbon （Vc） are revealed by electron spin resonance （ESR） technique at 110 K. The results strongly suggest that the green band luminescence, as shallow donor-deep accepter emission, is attributed to the vacancies of C and the extended defects. The broadband green luminescence spectrum can be fitted by the two Gauss-type spectra using nonlinear optimization technique. It shows that the broad-band green luminescence originates from the combination of two independent radiative transitions. The centers of two energy levels are located 2.378 and 2.130 eV below the conduction band, respectively, and the ends of two energy levels are expanded and superimposed each other.
基金supported by National Natural Science Foundation of China(Nos.51925206 and 52461160328)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0450301)the Fundamental Research Funds for the Central Universities(20720220009,WK2490000002).
文摘All-inorganic perovskites are advantageous in terms of improved thermal stability compared to organic-inorganic counterparts.However,the ion migration-induced hysteresis significantly undermines the long-term operational stability of all-inorganic perovskite solar cells(PSCs),particularly in mixed halide perovskites.Herein,we report that tin-lead(Sn-Pb)alloying for all-inorganic mixed halide perovskites can effectively inhibit the ion migration behavior,as comprehensively revealed by the time-of-flight secondary ion mass spectrometry(TOF-SIMS),optical microscopy and galvanostatic measurements.On one hand,the small-sized Sn2+cations can tighten the lattice structure to enhance the Pb/Sn-X(X=I and Br)ionic bonds,thereby effectively immobilizing the halide ions.On the other hand,Sn substitution can significantly reduce anti-site defects,such as I_(Cs)and I_(Pb),which are considered potential pathways for ion migration.With these advantages,ion migration is greatly suppressed in Sn-Pb alloyed inorganic perovskites,resulting in reduced hysteresis and improved operational stability of PSC devices.
基金supported by the National Natural Science Foundation of China(11374092,61474040,11204073)the National Basic Research Program of China(2012CB933703)the Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province and the Hunan Provincial Science and Technology Department(2014FJ2001,2014GK3015,2014TT1004)
文摘ZnSe nanoribbons were synthesized with chemical vapor deposition route. The excitation power-dependent photol and surface photovoltage （SPV） techniques were used to study the optoelectronic properties of the as-grown ZnSe nanoribbons. Three deep defect （DD）-related emission bands, respectively, centered at 623 nm （DD1）, 563 nm （DD2） and 525 nm （DD3）, emerge orderly with increasing the excitation power, which is attributed to the saturation of the DD states from deeper to shallower level. The SPV spectrum and the corresponding phase spectrum show that DD1 mainly acts as recombination center, while DD2 and DD3 can act as both the recombination center and electron traps. The influence of the trapping electrons on the SPV response dynamic was studied with transient SPV.
