The Study On Light Absorber And Counter Electrode Of Full Printable Perovskite Solar Cells

The ABX₃ halide perovskite formed cubic crystal structure with B formed octahedral framework with 6 halide ions and A occupied the cub octahedral voids neighboring with the 12 nearest halide ions.Halid perovskite solar cells have been investigated extensively owing to their large absorption coefficient over a wide spectral range,high carrier mobility as well as ambipolar charge transport,the simple preparation process etc.In past few years,the power conversion efficiency of perovskite solar cells increased rapidly from 3.8%in2009 to 22.7%in 2017.Among various device structures,fully printable perovskite solar cells based on inorganic metal oxides architecture of TiO₂/Al₂O₃（/NiO）/carbon has been promising photovoltaics due to its feature of being principally high stability and low cost.However,compare to the convential thin film perovskite solar cells,the full printable mesoporous perovskite solar cells show a lower device efficiency.Moreover,CH₃NH₃PbI₃always shows poor stability,which have been most widely investageted in various device structures.Considering above problems,in this thesis,we systematically explored the light absorber layer materials and counter electrode based on device structure of TiO₂/Al₂O₃（/NiO）/carbon,aming to promote the device efficiency and stability.The main contents of this thesis are listed as following:Triple cation perovskite of Cs_x(FA_0.4MA_0.6)_1-xPbI_2.8Br_0.2,for the first time,is introduced in fully printable perovskite solar cells on the basis of a mesoporous metal oxides TiO₂/Al₂O₃/NiO layered framework with carbon counter electrode.We find partial replacement FA/MA by Cs could increase the bandgap and exciton binding energy of Cs_x(FA_0.4MA_0.6)_1-xPbI_2.8Br_0.2 perovskite.An optimal efficiency of 17.02%can be obtained using Cs_0.05(FA_0.4MA_0.6)_0.95PbI_2.8Br_0.2 Detailed investigations with nanosecond transient absorption spectroscopy and transient photovoltage/photocurrent decay measurement reveal that the presence of Cs in perovskite compounds can increase charge carrier lifetime along with diffusion length benefiting for charge transport and reducing the recombination process in thick mesoscopic layers.The long diffusion length makes the devices with no space charge limit effect,which would effectively reduce the recombination process.Furthermore,the Cs_0.05(FA_0.4MA_0.6)_0.95PbI_2.8Br_0.2-based devices exhibit good stability with a retention of over 90%initial PCE after 1020 h in dark condition at 85 ^oC.The Cs（Pb:xBi）I₂Br perovskite is introduced to mesoporous metal oxides TiO₂/Al₂O₃/NiO layered framework.We find that the absorption onset is redshift systematically with the Bi contend increased.However,with the addition of Bi³⁺,the devices performance was severe decrease.To investigate the reasons for the poor performance of Bi³⁺doped devices,the time resolve fluorescence decay and electrochemical impedance spectroscopy measurements were performed.We find that the decreased performance mainly arrtibuted the increased recombination process.The NiO/SWCNT films show excellent conductivity and charge extraction ability.We find appreciated power conversion efficiency of 12.7%can be achieved for the CH₃NH₃PbI₃ perovskite solar cell using mesoscopic TiO₂/Al₂O₃ framework structure in combination with a thin NiO/SWCNT counter electrode under standard reporting conditions.Electronic impedance spectroscopy measurements reveal efficient charge collection ability for perovskite devices using thin NiO/SWCNT counter electrodes compared to the conventional carbon black/graphite counter electrode,and thus can efficiently deliver photocurrent.