Performance Enhancement Of Semitransparent Organic Solar Cells Via Interface Modification And Optical Adjustment

In recent years,semitransparent organic solar cells(ST-OSCs)exhibit promising prospects in building integrated photovoltaics(BIPVs)due to advantages of low cost,large-area manufactureing processg,bright and tunable colors.However,ST-OSCs must maintain excellent photoelectric conversion efficiency(PCE)while ensuring suitable average visible transmittance(AVT)and visually comfortable color(high color rendering index,CRI)for the application of photovoltaic glass windows.Therefore,the trade-off between the PCE and AVT/CRI is crucial for enhancing the performance of ST-OSCs.Herein,an in-depth investigation on regulating AVT,PCE and CRI was carried out via the synergistic effects of interface modification and optical coupling,and thus achieving high-performance ST-OSCs.The main research results are as follows:a.High-performance electron transport layers(ETLs)are vital to improve the performance of ST-OSCs.Gallium oxide(Ga2O3)and indium oxide(In2O3)films are good ETLs in perovskite solar cells and dye-sentisized solar cells,but their preparation processes either suffered from complexity or involved high-temperature thermal treatment.In this work,we obtained In2O3 and Ga2O3 films via a mild solution process of spin-coating In(acac)3 and Ga(acac)3 isopropanol precursor followed by a low temperature thermal treatment.The comparison studies present that both In2O3 and Ga2O3 films have higher than 95%transmittance within the whole visible range.Meanwhile,the In2O3 layer possesses a work function(WF)of 4.58 eV,which is more favorable for forming of ohmic contact than that of Ga2O3 with a WF of 5.06 eV,and leading to a higher open circuit voltage for the former devices.Then,the internal charge transfer process and their effects on devices were discussed through further investigations on electrochemical impedance spectra(EIS).The results show that In2O3 has lower series resistance loss,and Ga2O3 has higher recombination resistance.Finally,the PCEs of opaque devices with In2O3 or Ga2O3 ETL reach up to 16.17%and 16.01%,respectively.The corresponding PCEs for semitransparent devices are 12.71%and 12.60%,respectively.Notably,the AVTs of all devices exceed 25%,and the CRIs are also higher than 95.b.For ST-OSCs,the common approach for generating different colors is to adopt various photoactive layers,which complicates production processes and leads to process-induced performance deviations.In addition,the general thickness of photoactive layers for nonefullerene OSCs is about 100 nm,which is not thickner enough for fully absorpting the incident sunlight,but increasing the thickness of active layers will cause seriousrecombination and reduce the fill factor of devices.In order to improve the light absorption of devices and simultaneously realize multicolored devices independently from the active layer,we introduced a new type of electron transport layer Hf(ACB1)4 and Ag/MoO3/Ag microcavity.Research present that the hemispherical Hf(ACB1)4 nanoparticles can significantly improve the light absorption of devices,and the PCE based on PM6:BTP-eC9 OSCs gets up to 16.76%.Finally,under the guidance of optical simulation,the rationally designed ST-OSCs with Hf(ACB 1)4 ECL and Ag/MoO3/Ag display vibrant colors(purple,sky blue,cyan,green and magenta)independently from the inherent color of PM6:Y6 active material,and show a close to 12%PCE.Among them,the cyan device displayed a champion PCE of 11.91%with an AVT of 23.69%and a CRI of 92.5.The results show that interface modification and optical microcavity pave a promising way for realizing multicolored ST-OSCs with outstanding efficiency and visual comfort.