Study On Photovoltaic Performance And Ultraviolet Stability Of Perovskite Solar Cells

Perovskite materials possess great potential for development and application prospects in the photovoltaic field due to their excellent photoelectric properties,low cost and simple preparation process.Recently,the power conversion efficiency（PCE）of perovskite solar cells（PVSCs）has increased rapidly from 3.8%to 25.8%,but it is still below the theoretical limit defined by Shockley-Queisser（SQ）.In addition,the long-term stability of the perovskite film and their corresponding devices under ultraviolet（UV）conditions is an inevitable issue to be confronted towards commercialization.The aim of this research is to improve UV stability and photovoltaic performance through additive strategy and solvent engineering,in order to advance the commercialization of PVSCs.The UV stability of PVSCs is improved by introducing a6,13-bis（triisopropylsilylethynyl）pentacene（TIPS-PEN）layer with singlet fission down-conversion effect via one-step anti-solvent method.The introduction of down conversion layer can not only improve the short circuit photocurrent(J_sc)by converting UV light into multiple excitons,but also enhance the open-circuit voltage(V_oc)owing to a better matched energy level alignment at the perovskite/HTL interface.Consequently,the TIPS-PEN incorporated PVSCs attain the champion power conversion efficiency（PCE）up to 22.92%.As the light conversion effect of TIPE-PEN weakens the UV damage to perovskite,the UV stability of the device is dramatically improved,maintaining 80%of the initial PCE after 150 hours of continuous UV light exposure.In addition,the TIPS-PEN modified PVSCs also demonstrate excellent humidity stability,preserving over 80%of their original PCE after 1000 hours in ambient conditions（50%relative humidity,25°C）.The introduction of hexamethylphosphoramide（HMPA）into the Pb I₂ solution through a reasonable choice of second solvent forms a Lewis acid-base adduct intermediate phase to modulate the perovskite crystallization.On the one hand,HMPA solvent molecules have a large molecular volume and can pre-expand the Pb I₂lattice,regulating the plane spacing of Pb I₂ at a microscopic level.The broadened plane spacing not only provides intramolecular channels for the rapid penetration of FAI,but also partially counteracts the lattice expansion during the conversion of Pb I₂to perovskite.On the other hand,unlike the conventional conversion path of Pb I₂ to perovskite,which requires overcoming a high energy barrier,Pb I₂-HMPA can be converted toα-phase perovskite in situ at low temperature.In summary,premium-quality perovskite films are fabricated using HMPA and the corresponding devices exhibit the highest PCE（23.30%）.Moreover,the corresponding unencapsulated devices show significantly improved stability even after extended light and humidity stability tests.