Tunable multicolor luminescence in vanadates from yttrium to indium with enhanced luminous efficiency and stability for its application in WLEDs and indoor photovoltaics

The preparation of high-efficiency phosphor is the key to the construction of white light-emitting diode(WLED)devices and their application in indoor photovoltaics.Compared with YVO_(4),InVO_(4)is not suitable as the host material of lanthanide ions because of its strong self-luminescence.Here,the work focused on combining the broadband emission from InVO_(4)and the red luminescence from YVO_(4):Eu^(3+)to obtain enhanced and stable multicolor luminescence.The band structure,density of state,and optical properties were studied by density functional theory.The spectral configuration of YVO_(4):In^(3+)/Eu^(3+)with(112)surface appears to be broadening and redshifts with increasing layer number.When the In^(3+)concentration is 3.5 mol%,the YVO_(4):30%Eu^(3+)/In^(3+)emits the strongest light.The Judd-Ofelt parameterΩ2 of YVO_(4):In^(3+)/Eu^(3+)increases with increaing In^(3+)concentration,indicating that the symmetry decreases.By adjusting In^(3+)/Eu^(3+)contents,the YVO_(4):In^(3+)/Eu^(3+)not only can emit white light with a color rendering index of 95,but also can be used as high-efficiency red phosphor to build WLED devices with blue emitting N/Tb codoped carbon quantum dots(CQDs-N:Tb^(3+))and green emitting MOF:Tb^(3+)(MOF=metal organic framework),for which the color rendering index can also reach 95 and the color temperature is 5549 K.The manufactured WLED devices were further used to excite the silicon solar cell and make it show good photoelectric characteristics.

Organic photodiode with dual functions of indoor photovoltaic and high-speed photodetector

Energy harvesting and light detection are key technologies in various emerging optoelectronic applications.The high absorption capability and bandgap tunability of organic semiconductors make them promising candidates for such applications.Herein,a poly(3-hexylthiophene-2,5-diyl)(P3HT):indene-C60 bisadduct(ICBA)bulk heterojunction-based organic photodiode(OPD)was reported,demonstrating dual functionality as an indoor photovoltaic(PV)and as a high-speed photodetector.This OPD demonstrated decent indoor PV performance with a power conversion efficiency(PCE)of(11.6±0.5)%under a light emitting diode(LED)lamp with a luminance of 1000 lx.As a photodetector,this device exhibited a decent photoresponsivity of 0.15 A/W(green light)with an excellent linear dynamic range(LDR)of over 127 dB within the optical power range of 3.74×10^(−7) to 9.6×10^(−2) W/cm^(2).Furthermore,fast photoswitching behaviors could be observed with the rising/falling times of 14.5/10.4μs and a cutoff(3 dB)frequency of 37 kHz.These results might pave the way for further development of organic optoelectronic applications.

Simultaneous improving luminescence intensity and stability of CsPbBr_(3):SCN−@Eu/Zr-Uio-66-NH_(2) with tunable emissions from blue to green and applications in indoor photovoltaics

The construction of stable and efficient materials that emit blue and green light remains a challenge.Among the blue light materials reported,metal-organic framework(MOF)materials are rarely reported as blue phosphors due to their weak luminescence intensity.Based on the construction of CsPbBr_(3)@MOF(CPB@MOF),an innovative idea was proposed to simultaneously enhance the green luminescence of CPB and the blue luminescence of MOF through the interaction between CPB and MOF for the first time.As expected,the blue luminescence from CPB:7%SCN−@0.5%MOF:Eu as well as the green luminescence from 5%CPB:7%SCN−@MOF:Eu was sufficient to construct high-performance light-emitting diode(LED)devices and further excite solar cells to generate stable photoelectric signals.The white LED(WLED)device with excellent color quality(color rendering index(CRI)=96.2)and correlated color temperature(CCT=9688 K)can be constructed by using the obtained blue-emitting CPB:7%SCN-@0.5%MOF:Eu,green-emitting 5%CPB:7%SCN−@MOF:Eu,and red-emitting PPB:30%Mn^(2+).The density functional theory(DFT)theoretical calculation results indicate that the p orbital of Pb plays the major role in the conduction band,and the p orbital of Br plays the major role in the valance band of CPB and CPB:SCN−.While the p orbital of O plays the major role in both the conduction band and valance band of MOF.The heat capacity of CPB and CPB:SCN−separately reaches the Dulong–Petit limit at 200 and 400 K,indicating that the thermal stability of CsPbBr_(3)increases after SCN−doping.

Theoretical efficiency limit and realistic losses of indoor organic and perovskite photovoltaics [Invited]

Indoor organic and perovskite photovoltaics(PVs)have been attracting great interest in recent years.The theoretical limit of indoor PVs has been calculated based on the detailed balance method developed by Shockley–Queisser.However,realistic losses of the organic and perovskite PVs under indoor illumination are to be understood for further efficiency improvement.In this work,the efficiency limit of indoor PVs is calculated to 55.33%under indoor illumination(2700 K,1000 lux)when the bandgap(E_(g))of the semiconductor is 1.77 eV.The efficiency limit was obtained on the basis of assuming 100%photovoltaic external quantum efficiency(EQ_(EPV))when E≥E_(g),there was no nonradiative recombination,and there were no resistance losses.In reality,the maximum EQEPV reported in the literature is 0.80–0.90.The proportion of radiative recombination in realistic devices is only 10^(−5)–10^(−2),which causes the open-circuit voltage loss(ΔV_(loss))of 0.12–0.3 V.The fill factor(FF)of the indoor PVs is sensitive to the shunt resistance(R_(sh)).The realistic losses of EQE_(PV),nonradiative recombination,and resistance cause the large efficiency gap between the realistic values(excellent perovskite indoor PV,32.4%;superior organic indoor PV,30.2%)and the theoretical limit of 55.33%.In reality,it is feasible to reach the efficiency of 47.4%at 1.77 eV for organic and perovskite photovoltaics under indoor light(1000 lux,2700 K)with V_(OC)=1.299 V,J_(SC)=125.33μA/cm^(2),and FF=0.903 when EQE_(PV)=0.9,EQE_(EL)=10^(−1),R_(s)=0.5Ωcm^(2),and R_(sh)=10^(4) kΩcm^(2).

高性能、光冲击稳定的钙钛矿室内光伏器件

Perovskite solar cells offer great potential as a sustainable power source for distributed electronic devices that operate indoors.However,the impact of advanced lighting technology,especially the widely used pulse width modulation(PWM)technology,on perovskite photovoltaics has been ignored.Herein,for the first time in photovoltaics,we find that the light impact emitted by the PWM lighting system caused dynamic strain in perovskite thin films,induced phase separation,and accelerated the generation of metallic lead(Pb^(0))defects,leading to irreversible degradation of the cell performance after 27 h(T_(80)).To address this issue,formamidinium triiodide(FAI_(3))is chosen to treat the surface of the perovskite and release residual stress,resulting in reduced lattice deformation during dynamic strain processes.Meanwhile,it suppresses harmful Pb0 defects and reduces Voc loss at low light intensity.The champion device achieves impressive power conversion efficiency(PCE)of 35.14%and retains 99.5%of the initial PCE after continuous strobe light soaking for 2160 h.

The issues on the commercialization of perovskite solar cells

Perovskite solar cells have aroused a worldwide research upsurge in recent years due to their soaring photovoltaic performance,ease of solution processing,and low cost.The power conversion efficiency record is constantly being broken and has recently reached 26.1%in the lab,which is comparable to the established photovoltaic technologies such as crystalline silicon,copper indium gallium selenide and cadmium telluride(CdTe)solar cells.Currently,perovskite solar cells are standing at the entrance of industrialization,where huge opportunities and risks coexist.However,towards commercialization,challenges of up-scaling,stability and lead toxicity still remain,the proper handling of which could potentially lead to the widespread adoption of perovskite solar cells as a low-cost and efficient source of renewable energy.This review gives a holistic analysis of the path towards commercialization for perovskite solar cells.A comprehensive overview of the current state-of-the-art level for perovskite solar cells and modules will be introduced first,with respect to the module efficiency,stability and current status of industrialization.We will then discuss the challenges that get in the way of commercialization and the corresponding strategies to address them,involving the upscaling,the stability and the lead toxicity issue.Insights into the future direction of commercialization of perovskite photovoltaics was also provided,including the flexible perovskite cells and modules and perovskite indoor photovoltaics.Finally,the future perspectives towards commercialization are put forward.